Refactor and add much more robust tests (both automated and manual) to ensure loops and things work ok

.forgejo/workflows/lint.yml

@@ -15,7 +15,7 @@ jobs:
         run: |
           apt-get update
           DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
-            black pyflakes3 python3-bandit
+            black pyflakes3 python3-bandit vulture
 
       - name: Run linters
         run: |
@@ -24,3 +24,4 @@ jobs:
           pyflakes3 src/*
           pyflakes3 tests/*
           bandit -s B110 -r src/
+          vulture .

.gitignore

@@ -7,3 +7,4 @@ dist
 *.yml
 *.j2
 *.toml
+regenerated_*

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "jinjaturtle"
-version = "0.2.0"
+version = "0.3.0"
 description = "Convert config files into Ansible defaults and Jinja2 templates."
 authors = ["Miguel Jacq <mig@mig5.net>"]
 license = "GPL-3.0-or-later"

src/jinjaturtle/core.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 from pathlib import Path
 from typing import Any, Iterable
 
+import datetime
 import yaml
 
 from .loop_analyzer import LoopAnalyzer, LoopCandidate
@@ -100,6 +101,9 @@ def parse_config(path: Path, fmt: str | None = None) -> tuple[str, Any]:
     if handler is None:
         raise ValueError(f"Unsupported config format: {fmt}")
     parsed = handler.parse(path)
+    # Make sure datetime objects are treated as strings (TOML, YAML)
+    parsed = _stringify_timestamps(parsed)
+
     return fmt, parsed
 
 
@@ -158,17 +162,6 @@ def _path_starts_with(path: tuple[str, ...], prefix: tuple[str, ...]) -> bool:
     return path[: len(prefix)] == prefix
 
 
-def _normalize_default_value(value: Any) -> Any:
-    """
-    Ensure that 'true' / 'false' end up as quoted strings in YAML.
-    """
-    if isinstance(value, bool):
-        return QuotedString("true" if value else "false")
-    if isinstance(value, str) and value.lower() in {"true", "false"}:
-        return QuotedString(value)
-    return value
-
-
 def generate_ansible_yaml(
     role_prefix: str,
     flat_items: list[tuple[tuple[str, ...], Any]],
@@ -182,7 +175,7 @@ def generate_ansible_yaml(
     # Add scalar variables
     for path, value in flat_items:
         var_name = make_var_name(role_prefix, path)
-        defaults[var_name] = _normalize_default_value(value)
+        defaults[var_name] = value  # No normalization - keep original types
 
     # Add loop collections
     if loop_candidates:
@@ -226,3 +219,29 @@ def generate_jinja2_template(
     return handler.generate_jinja2_template(
         parsed, role_prefix, original_text=original_text
     )
+
+
+def _stringify_timestamps(obj: Any) -> Any:
+    """
+    Recursively walk a parsed config and turn any datetime/date/time objects
+    into plain strings in ISO-8601 form.
+
+    This prevents Python datetime objects from leaking into YAML/Jinja, which
+    would otherwise reformat the value (e.g. replacing 'T' with a space).
+
+    This commonly occurs otherwise with TOML and YAML files, which sees
+    Python automatically convert those sorts of strings into datetime objects.
+    """
+    if isinstance(obj, dict):
+        return {k: _stringify_timestamps(v) for k, v in obj.items()}
+    if isinstance(obj, list):
+        return [_stringify_timestamps(v) for v in obj]
+
+    # TOML & YAML both use the standard datetime types
+    if isinstance(obj, datetime.datetime):
+        # Use default ISO-8601: 'YYYY-MM-DDTHH:MM:SS±HH:MM' (with 'T')
+        return obj.isoformat()
+    if isinstance(obj, (datetime.date, datetime.time)):
+        return obj.isoformat()
+
+    return obj

src/jinjaturtle/handlers/ini.py

@@ -12,7 +12,7 @@ class IniHandler(BaseHandler):
 
     def parse(self, path: Path) -> configparser.ConfigParser:
         parser = configparser.ConfigParser()
-        parser.optionxform = str  # preserve key case
+        parser.optionxform = str  # noqa
         with path.open("r", encoding="utf-8") as f:
             parser.read_file(f)
         return parser

src/jinjaturtle/handlers/json.py

@@ -1,10 +1,12 @@
 from __future__ import annotations
 
 import json
+import re
 from pathlib import Path
 from typing import Any
 
 from . import DictLikeHandler
+from ..loop_analyzer import LoopCandidate
 
 
 class JsonHandler(DictLikeHandler):
@@ -21,17 +23,38 @@ class JsonHandler(DictLikeHandler):
         role_prefix: str,
         original_text: str | None = None,
     ) -> str:
+        """Original scalar-only template generation."""
         if not isinstance(parsed, (dict, list)):
             raise TypeError("JSON parser result must be a dict or list")
         # As before: ignore original_text and rebuild structurally
         return self._generate_json_template(role_prefix, parsed)
 
+    def generate_jinja2_template_with_loops(
+        self,
+        parsed: Any,
+        role_prefix: str,
+        original_text: str | None,
+        loop_candidates: list[LoopCandidate],
+    ) -> str:
+        """Generate template with Jinja2 for loops where appropriate."""
+        if not isinstance(parsed, (dict, list)):
+            raise TypeError("JSON parser result must be a dict or list")
+
+        # Build loop path set for quick lookup
+        loop_paths = {candidate.path for candidate in loop_candidates}
+
+        return self._generate_json_template_with_loops(
+            role_prefix, parsed, loop_paths, loop_candidates
+        )
+
     def _generate_json_template(self, role_prefix: str, data: Any) -> str:
         """
         Generate a JSON Jinja2 template from parsed JSON data.
 
         All scalar values are replaced with Jinja expressions whose names are
         derived from the path, similar to TOML/YAML.
+
+        Uses | tojson filter to preserve types (numbers, booleans, null).
         """
 
         def _walk(obj: Any, path: tuple[str, ...] = ()) -> Any:
@@ -39,9 +62,130 @@ class JsonHandler(DictLikeHandler):
                 return {k: _walk(v, path + (str(k),)) for k, v in obj.items()}
             if isinstance(obj, list):
                 return [_walk(v, path + (str(i),)) for i, v in enumerate(obj)]
-            # scalar
+            # scalar - use marker that will be replaced with tojson
             var_name = self.make_var_name(role_prefix, path)
-            return f"{{{{ {var_name} }}}}"
+            return f"__SCALAR__{var_name}__"
 
         templated = _walk(data)
-        return json.dumps(templated, indent=2, ensure_ascii=False) + "\n"
+        json_str = json.dumps(templated, indent=2, ensure_ascii=False)
+
+        # Replace scalar markers with Jinja expressions using tojson filter
+        # This preserves types (numbers stay numbers, booleans stay booleans)
+        json_str = re.sub(
+            r'"__SCALAR__([a-zA-Z_][a-zA-Z0-9_]*)__"', r"{{ \1 | tojson }}", json_str
+        )
+
+        return json_str + "\n"
+
+    def _generate_json_template_with_loops(
+        self,
+        role_prefix: str,
+        data: Any,
+        loop_paths: set[tuple[str, ...]],
+        loop_candidates: list[LoopCandidate],
+        path: tuple[str, ...] = (),
+    ) -> str:
+        """
+        Generate a JSON Jinja2 template with for loops where appropriate.
+        """
+
+        def _walk(obj: Any, current_path: tuple[str, ...] = ()) -> Any:
+            # Check if this path is a loop candidate
+            if current_path in loop_paths:
+                # Find the matching candidate
+                candidate = next(c for c in loop_candidates if c.path == current_path)
+                collection_var = self.make_var_name(role_prefix, candidate.path)
+                item_var = candidate.loop_var
+
+                if candidate.item_schema == "scalar":
+                    # Simple list of scalars - use special marker that we'll replace
+                    return f"__LOOP_SCALAR__{collection_var}__{item_var}__"
+                elif candidate.item_schema in ("simple_dict", "nested"):
+                    # List of dicts - use special marker
+                    return f"__LOOP_DICT__{collection_var}__{item_var}__"
+
+            if isinstance(obj, dict):
+                return {k: _walk(v, current_path + (str(k),)) for k, v in obj.items()}
+            if isinstance(obj, list):
+                # Check if this list is a loop candidate
+                if current_path in loop_paths:
+                    # Already handled above
+                    return _walk(obj, current_path)
+                return [_walk(v, current_path + (str(i),)) for i, v in enumerate(obj)]
+
+            # scalar - use marker to preserve type
+            var_name = self.make_var_name(role_prefix, current_path)
+            return f"__SCALAR__{var_name}__"
+
+        templated = _walk(data, path)
+
+        # Convert to JSON string
+        json_str = json.dumps(templated, indent=2, ensure_ascii=False)
+
+        # Replace scalar markers with Jinja expressions using tojson filter
+        json_str = re.sub(
+            r'"__SCALAR__([a-zA-Z_][a-zA-Z0-9_]*)__"', r"{{ \1 | tojson }}", json_str
+        )
+
+        # Post-process to replace loop markers with actual Jinja loops
+        for candidate in loop_candidates:
+            collection_var = self.make_var_name(role_prefix, candidate.path)
+            item_var = candidate.loop_var
+
+            if candidate.item_schema == "scalar":
+                # Replace scalar loop marker with Jinja for loop
+                marker = f'"__LOOP_SCALAR__{collection_var}__{item_var}__"'
+                replacement = self._generate_json_scalar_loop(
+                    collection_var, item_var, candidate
+                )
+                json_str = json_str.replace(marker, replacement)
+
+            elif candidate.item_schema in ("simple_dict", "nested"):
+                # Replace dict loop marker with Jinja for loop
+                marker = f'"__LOOP_DICT__{collection_var}__{item_var}__"'
+                replacement = self._generate_json_dict_loop(
+                    collection_var, item_var, candidate
+                )
+                json_str = json_str.replace(marker, replacement)
+
+        return json_str + "\n"
+
+    def _generate_json_scalar_loop(
+        self, collection_var: str, item_var: str, candidate: LoopCandidate
+    ) -> str:
+        """Generate a Jinja for loop for a scalar list in JSON."""
+        # Use tojson filter to properly handle strings (quotes them) and other types
+        # Include array brackets around the loop
+        return (
+            f"[{{% for {item_var} in {collection_var} %}}"
+            f"{{{{ {item_var} | tojson }}}}"
+            f"{{% if not loop.last %}}, {{% endif %}}"
+            f"{{% endfor %}}]"
+        )
+
+    def _generate_json_dict_loop(
+        self, collection_var: str, item_var: str, candidate: LoopCandidate
+    ) -> str:
+        """Generate a Jinja for loop for a dict list in JSON."""
+        if not candidate.items:
+            return "[]"
+
+        # Get first item as template
+        sample_item = candidate.items[0]
+
+        # Build the dict template - use tojson for all values to handle types correctly
+        fields = []
+        for key, value in sample_item.items():
+            if key == "_key":
+                continue
+            # Use tojson filter to properly serialize all types (strings, numbers, booleans)
+            fields.append(f'"{key}": {{{{ {item_var}.{key} | tojson }}}}')
+
+        dict_template = "{" + ", ".join(fields) + "}"
+
+        return (
+            f"{{% for {item_var} in {collection_var} %}}"
+            f"{dict_template}"
+            f"{{% if not loop.last %}}, {{% endif %}}"
+            f"{{% endfor %}}"
+        )

src/jinjaturtle/handlers/toml.py

@@ -5,6 +5,7 @@ from pathlib import Path
 from typing import Any
 
 from . import DictLikeHandler
+from ..loop_analyzer import LoopCandidate
 
 
 class TomlHandler(DictLikeHandler):
@@ -25,12 +26,31 @@ class TomlHandler(DictLikeHandler):
         role_prefix: str,
         original_text: str | None = None,
     ) -> str:
+        """Original scalar-only template generation."""
         if original_text is not None:
             return self._generate_toml_template_from_text(role_prefix, original_text)
         if not isinstance(parsed, dict):
             raise TypeError("TOML parser result must be a dict")
         return self._generate_toml_template(role_prefix, parsed)
 
+    def generate_jinja2_template_with_loops(
+        self,
+        parsed: Any,
+        role_prefix: str,
+        original_text: str | None,
+        loop_candidates: list[LoopCandidate],
+    ) -> str:
+        """Generate template with Jinja2 for loops where appropriate."""
+        if original_text is not None:
+            return self._generate_toml_template_with_loops_from_text(
+                role_prefix, original_text, loop_candidates
+            )
+        if not isinstance(parsed, dict):
+            raise TypeError("TOML parser result must be a dict")
+        return self._generate_toml_template_with_loops(
+            role_prefix, parsed, loop_candidates
+        )
+
     def _generate_toml_template(self, role_prefix: str, data: dict[str, Any]) -> str:
         """
         Generate a TOML Jinja2 template from parsed TOML dict.
@@ -45,6 +65,89 @@ class TomlHandler(DictLikeHandler):
             var_name = self.make_var_name(role_prefix, path + (key,))
             if isinstance(value, str):
                 lines.append(f'{key} = "{{{{ {var_name} }}}}"')
+            elif isinstance(value, bool):
+                # Booleans need | lower filter (Python True/False → TOML true/false)
+                lines.append(f"{key} = {{{{ {var_name} | lower }}}}")
+            else:
+                lines.append(f"{key} = {{{{ {var_name} }}}}")
+
+        def walk(obj: dict[str, Any], path: tuple[str, ...] = ()) -> None:
+            scalar_items = {k: v for k, v in obj.items() if not isinstance(v, dict)}
+            nested_items = {k: v for k, v in obj.items() if isinstance(v, dict)}
+
+            if path:
+                header = ".".join(path)
+                lines.append(f"[{header}]")
+
+            for key, val in scalar_items.items():
+                emit_kv(path, str(key), val)
+
+            if scalar_items:
+                lines.append("")
+
+            for key, val in nested_items.items():
+                walk(val, path + (str(key),))
+
+        # Root scalars (no table header)
+        root_scalars = {k: v for k, v in data.items() if not isinstance(v, dict)}
+        for key, val in root_scalars.items():
+            emit_kv((), str(key), val)
+        if root_scalars:
+            lines.append("")
+
+        # Tables
+        for key, val in data.items():
+            if isinstance(val, dict):
+                walk(val, (str(key),))
+
+        return "\n".join(lines).rstrip() + "\n"
+
+    def _generate_toml_template_with_loops(
+        self,
+        role_prefix: str,
+        data: dict[str, Any],
+        loop_candidates: list[LoopCandidate],
+    ) -> str:
+        """
+        Generate a TOML Jinja2 template with for loops where appropriate.
+        """
+        lines: list[str] = []
+        loop_paths = {candidate.path for candidate in loop_candidates}
+
+        def emit_kv(path: tuple[str, ...], key: str, value: Any) -> None:
+            var_name = self.make_var_name(role_prefix, path + (key,))
+            if isinstance(value, str):
+                lines.append(f'{key} = "{{{{ {var_name} }}}}"')
+            elif isinstance(value, bool):
+                # Booleans need | lower filter (Python True/False → TOML true/false)
+                lines.append(f"{key} = {{{{ {var_name} | lower }}}}")
+            elif isinstance(value, list):
+                # Check if this list is a loop candidate
+                if path + (key,) in loop_paths:
+                    # Find the matching candidate
+                    candidate = next(
+                        c for c in loop_candidates if c.path == path + (key,)
+                    )
+                    collection_var = self.make_var_name(role_prefix, candidate.path)
+                    item_var = candidate.loop_var
+
+                    if candidate.item_schema == "scalar":
+                        # Scalar list loop
+                        lines.append(
+                            f"{key} = ["
+                            f"{{% for {item_var} in {collection_var} %}}"
+                            f"{{{{ {item_var} }}}}"
+                            f"{{% if not loop.last %}}, {{% endif %}}"
+                            f"{{% endfor %}}"
+                            f"]"
+                        )
+                    elif candidate.item_schema in ("simple_dict", "nested"):
+                        # Dict list loop - TOML array of tables
+                        # This is complex for TOML, using simplified approach
+                        lines.append(f"{key} = {{{{ {var_name} | tojson }}}}")
+                else:
+                    # Not a loop, treat as regular variable
+                    lines.append(f"{key} = {{{{ {var_name} }}}}")
             else:
                 lines.append(f"{key} = {{{{ {var_name} }}}}")
 
@@ -173,6 +276,236 @@ class TomlHandler(DictLikeHandler):
                         nested_var = self.make_var_name(role_prefix, nested_path)
                         if isinstance(sub_val, str):
                             inner_bits.append(f'{sub_key} = "{{{{ {nested_var} }}}}"')
+                        elif isinstance(sub_val, bool):
+                            inner_bits.append(
+                                f"{sub_key} = {{{{ {nested_var} | lower }}}}"
+                            )
+                        else:
+                            inner_bits.append(f"{sub_key} = {{{ {nested_var} }}}")
+                    replacement_value = "{ " + ", ".join(inner_bits) + " }"
+                    new_content = (
+                        before_eq + "=" + leading_ws + replacement_value + comment_part
+                    )
+                    out_lines.append(new_content + newline)
+                    continue
+                # If parsing fails, fall through to normal handling
+
+            # Normal scalar value handling (including bools, numbers, strings)
+            var_name = self.make_var_name(role_prefix, path)
+            use_quotes = (
+                len(raw_value) >= 2
+                and raw_value[0] == raw_value[-1]
+                and raw_value[0] in {'"', "'"}
+            )
+
+            # Check if value is a boolean in the text
+            is_bool = raw_value.strip().lower() in ("true", "false")
+
+            if use_quotes:
+                quote_char = raw_value[0]
+                replacement_value = f"{quote_char}{{{{ {var_name} }}}}{quote_char}"
+            elif is_bool:
+                replacement_value = f"{{{{ {var_name} | lower }}}}"
+            else:
+                replacement_value = f"{{{{ {var_name} }}}}"
+
+            new_content = (
+                before_eq + "=" + leading_ws + replacement_value + comment_part
+            )
+            out_lines.append(new_content + newline)
+
+        return "".join(out_lines)
+
+    def _generate_toml_template_with_loops_from_text(
+        self, role_prefix: str, text: str, loop_candidates: list[LoopCandidate]
+    ) -> str:
+        """
+        Generate a Jinja2 template for a TOML file with loop support.
+        """
+        loop_paths = {candidate.path for candidate in loop_candidates}
+        lines = text.splitlines(keepends=True)
+        current_table: tuple[str, ...] = ()
+        out_lines: list[str] = []
+        skip_until_next_table = (
+            False  # Track when we're inside a looped array-of-tables
+        )
+
+        for raw_line in lines:
+            line = raw_line
+            stripped = line.lstrip()
+
+            # Blank or pure comment
+            if not stripped or stripped.startswith("#"):
+                # Only output if we're not skipping
+                if not skip_until_next_table:
+                    out_lines.append(raw_line)
+                continue
+
+            # Table header: [server] or [server.tls] or [[array.of.tables]]
+            if stripped.startswith("[") and "]" in stripped:
+                header = stripped
+                # Check if it's array-of-tables ([[name]]) or regular table ([name])
+                is_array_table = header.startswith("[[") and "]]" in header
+
+                if is_array_table:
+                    # Extract content between [[ and ]]
+                    start = header.find("[[") + 2
+                    end = header.find("]]", start)
+                    inner = header[start:end].strip() if end != -1 else ""
+                else:
+                    # Extract content between [ and ]
+                    start = header.find("[") + 1
+                    end = header.find("]", start)
+                    inner = header[start:end].strip() if end != -1 else ""
+
+                if inner:
+                    parts = [p.strip() for p in inner.split(".") if p.strip()]
+                    table_path = tuple(parts)
+
+                    # Check if this is an array-of-tables that's a loop candidate
+                    if is_array_table and table_path in loop_paths:
+                        # If we're already skipping this table, this is a subsequent occurrence
+                        if skip_until_next_table and current_table == table_path:
+                            # This is a duplicate [[table]] - skip it
+                            continue
+
+                        # This is the first occurrence - generate the loop
+                        current_table = table_path
+                        candidate = next(
+                            c for c in loop_candidates if c.path == table_path
+                        )
+
+                        # Generate the loop header
+                        collection_var = self.make_var_name(role_prefix, candidate.path)
+                        item_var = candidate.loop_var
+
+                        # Get sample item to build template
+                        if candidate.items:
+                            sample_item = candidate.items[0]
+
+                            # Build loop
+                            out_lines.append(
+                                f"{{% for {item_var} in {collection_var} %}}\n"
+                            )
+                            out_lines.append(f"[[{'.'.join(table_path)}]]\n")
+
+                            # Add fields from sample item
+                            for key, value in sample_item.items():
+                                if key == "_key":
+                                    continue
+                                if isinstance(value, str):
+                                    out_lines.append(
+                                        f'{key} = "{{{{ {item_var}.{key} }}}}"\n'
+                                    )
+                                else:
+                                    out_lines.append(
+                                        f"{key} = {{{{ {item_var}.{key} }}}}\n"
+                                    )
+
+                            out_lines.append("{% endfor %}\n")
+
+                        # Skip all content until the next different table
+                        skip_until_next_table = True
+                        continue
+                    else:
+                        # Regular table or non-loop array - reset skip flag if it's a different table
+                        if current_table != table_path:
+                            skip_until_next_table = False
+                        current_table = table_path
+
+                out_lines.append(raw_line)
+                continue
+
+            # If we're inside a skipped array-of-tables section, skip this line
+            if skip_until_next_table:
+                continue
+
+            # Try key = value
+            newline = ""
+            content = raw_line
+            if content.endswith("\r\n"):
+                newline = "\r\n"
+                content = content[:-2]
+            elif content.endswith("\n"):
+                newline = content[-1]
+                content = content[:-1]
+
+            eq_index = content.find("=")
+            if eq_index == -1:
+                out_lines.append(raw_line)
+                continue
+
+            before_eq = content[:eq_index]
+            after_eq = content[eq_index + 1 :]
+
+            key = before_eq.strip()
+            if not key:
+                out_lines.append(raw_line)
+                continue
+
+            # Whitespace after '='
+            value_ws_len = len(after_eq) - len(after_eq.lstrip(" \t"))
+            leading_ws = after_eq[:value_ws_len]
+            value_and_comment = after_eq[value_ws_len:]
+
+            value_part, comment_part = self._split_inline_comment(
+                value_and_comment, {"#"}
+            )
+            raw_value = value_part.strip()
+
+            # Path for this key (table + key)
+            path = current_table + (key,)
+
+            # Check if this path is a loop candidate
+            if path in loop_paths:
+                candidate = next(c for c in loop_candidates if c.path == path)
+                collection_var = self.make_var_name(role_prefix, candidate.path)
+                item_var = candidate.loop_var
+
+                if candidate.item_schema == "scalar":
+                    # Scalar list loop
+                    replacement_value = (
+                        f"["
+                        f"{{% for {item_var} in {collection_var} %}}"
+                        f"{{{{ {item_var} }}}}"
+                        f"{{% if not loop.last %}}, {{% endif %}}"
+                        f"{{% endfor %}}"
+                        f"]"
+                    )
+                else:
+                    # Dict/nested loop - use tojson filter for complex arrays
+                    replacement_value = f"{{{{ {collection_var} | tojson }}}}"
+
+                new_content = (
+                    before_eq + "=" + leading_ws + replacement_value + comment_part
+                )
+                out_lines.append(new_content + newline)
+                continue
+
+            # Special case: inline table
+            if (
+                raw_value.startswith("{")
+                and raw_value.endswith("}")
+                and tomllib is not None
+            ):
+                try:
+                    # Parse the inline table as a tiny TOML document
+                    mini_source = "table = " + raw_value + "\n"
+                    mini_data = tomllib.loads(mini_source)["table"]
+                except Exception:
+                    mini_data = None
+
+                if isinstance(mini_data, dict):
+                    inner_bits: list[str] = []
+                    for sub_key, sub_val in mini_data.items():
+                        nested_path = path + (sub_key,)
+                        nested_var = self.make_var_name(role_prefix, nested_path)
+                        if isinstance(sub_val, str):
+                            inner_bits.append(f'{sub_key} = "{{{{ {nested_var} }}}}"')
+                        elif isinstance(sub_val, bool):
+                            inner_bits.append(
+                                f"{sub_key} = {{{{ {nested_var} | lower }}}}"
+                            )
                         else:
                             inner_bits.append(f"{sub_key} = {{{{ {nested_var} }}}}")
                     replacement_value = "{ " + ", ".join(inner_bits) + " }"
@@ -191,9 +524,14 @@ class TomlHandler(DictLikeHandler):
                 and raw_value[0] in {'"', "'"}
             )
 
+            # Check if value is a boolean in the text
+            is_bool = raw_value.strip().lower() in ("true", "false")
+
             if use_quotes:
                 quote_char = raw_value[0]
                 replacement_value = f"{quote_char}{{{{ {var_name} }}}}{quote_char}"
+            elif is_bool:
+                replacement_value = f"{{{{ {var_name} | lower }}}}"
             else:
                 replacement_value = f"{{{{ {var_name} }}}}"
 

src/jinjaturtle/handlers/xml.py

@@ -418,8 +418,8 @@ class XmlHandler(BaseHandler):
                 # Use simple variable reference - attributes should always exist
                 elem.set(attr_name, f"{{{{ {loop_var}.{attr_name} }}}}")
             elif key == "_text":
-                # Simple text content
-                elem.text = f"{{{{ {loop_var} }}}}"
+                # Simple text content - use ._text accessor for dict-based items
+                elem.text = f"{{{{ {loop_var}._text }}}}"
             elif key == "value":
                 # Text with attributes/children
                 elem.text = f"{{{{ {loop_var}.value }}}}"

src/jinjaturtle/handlers/yaml.py

@@ -124,7 +124,8 @@ class YamlHandler(DictLikeHandler):
                     replacement = f"{{{{ {var_name} }}}}"
 
                 leading = rest[: len(rest) - len(rest.lstrip(" \t"))]
-                new_stripped = f"{key}: {leading}{replacement}{comment_part}"
+                new_rest = f"{leading}{replacement}{comment_part}"
+                new_stripped = f"{key}:{new_rest}"
                 out_lines.append(
                     " " * indent
                     + new_stripped
@@ -281,7 +282,8 @@ class YamlHandler(DictLikeHandler):
                     replacement = f"{{{{ {var_name} }}}}"
 
                 leading = rest[: len(rest) - len(rest.lstrip(" \t"))]
-                new_stripped = f"{key}: {leading}{replacement}{comment_part}"
+                new_rest = f"{leading}{replacement}{comment_part}"
+                new_stripped = f"{key}:{new_rest}"
                 out_lines.append(
                     " " * indent
                     + new_stripped
@@ -378,10 +380,10 @@ class YamlHandler(DictLikeHandler):
             # Dict-style: key: {% for ... %}
             key = candidate.path[-1] if candidate.path else "items"
             lines.append(f"{indent_str}{key}:")
-            lines.append(f"{indent_str}  {{% for {item_var} in {collection_var} %}}")
+            lines.append(f"{indent_str}  {{% for {item_var} in {collection_var} -%}}")
         else:
             # List-style: just the loop
-            lines.append(f"{indent_str}{{% for {item_var} in {collection_var} %}}")
+            lines.append(f"{indent_str}{{% for {item_var} in {collection_var} -%}}")
 
         # Generate template for item structure
         if candidate.items:

src/jinjaturtle/loop_analyzer.py

@@ -85,14 +85,20 @@ class LoopAnalyzer:
             self._analyze_xml(parsed)
         elif fmt in ("yaml", "json", "toml"):
             self._analyze_dict_like(parsed, path=())
-        # INI files are typically flat key-value, not suitable for loops
+        elif fmt == "ini":
+            # INI files are typically flat key-value, not suitable for loops
+            pass
 
         # Sort by path depth (process parent structures before children)
         self.candidates.sort(key=lambda c: len(c.path))
         return self.candidates
 
     def _analyze_dict_like(
-        self, obj: Any, path: tuple[str, ...], depth: int = 0
+        self,
+        obj: Any,
+        path: tuple[str, ...],
+        depth: int = 0,
+        parent_is_list: bool = False,
     ) -> None:
         """Recursively analyze dict/list structures."""
 
@@ -111,9 +117,16 @@ class LoopAnalyzer:
 
             # Recurse into dict values
             for key, value in obj.items():
-                self._analyze_dict_like(value, path + (str(key),), depth + 1)
+                self._analyze_dict_like(
+                    value, path + (str(key),), depth + 1, parent_is_list=False
+                )
 
         elif isinstance(obj, list):
+            # Don't create loop candidates for nested lists (lists inside lists)
+            # These are too complex for clean template generation and should fall back to scalar handling
+            if parent_is_list:
+                return
+
             # Check if this list is homogeneous
             if len(obj) >= self.MIN_ITEMS_FOR_LOOP:
                 candidate = self._check_list_collection(obj, path)
@@ -123,8 +136,11 @@ class LoopAnalyzer:
                     return
 
             # If not a good loop candidate, recurse into items
+            # Pass parent_is_list=True so nested lists won't create loop candidates
             for i, item in enumerate(obj):
-                self._analyze_dict_like(item, path + (str(i),), depth + 1)
+                self._analyze_dict_like(
+                    item, path + (str(i),), depth + 1, parent_is_list=True
+                )
 
     def _check_list_collection(
         self, items: list[Any], path: tuple[str, ...]
@@ -185,45 +201,55 @@ class LoopAnalyzer:
 
         Example: {"server1": {...}, "server2": {...}} where all values
         have the same structure.
+
+        NOTE: Currently disabled for TOML compatibility. TOML's dict-of-tables
+        syntax ([servers.alpha], [servers.beta]) cannot be easily converted to
+        loops without restructuring the entire TOML format. To maintain consistency
+        between Ansible YAML and Jinja2 templates, we treat these as scalars.
         """
 
-        if not obj:
-            return None
-
-        values = list(obj.values())
-
-        # Check type homogeneity
-        value_types = [type(v).__name__ for v in values]
-        type_counts = Counter(value_types)
-
-        if len(type_counts) != 1:
-            return None
-
-        value_type = value_types[0]
-
-        # Only interested in dict values for dict collections
-        # (scalar-valued dicts stay as scalars)
-        if value_type != "dict":
-            return None
-
-        # Check structural homogeneity
-        schema = self._analyze_dict_schema(values)
-        if schema in ("simple_dict", "homogeneous"):
-            confidence = 0.9 if schema == "simple_dict" else 0.8
-
-            # Convert dict to list of items with 'key' added
-            items_with_keys = [{"_key": k, **v} for k, v in obj.items()]
-
-            return LoopCandidate(
-                path=path,
-                loop_var=self._derive_loop_var(path, singular=True),
-                items=items_with_keys,
-                item_schema="simple_dict",
-                confidence=confidence,
-            )
-
+        # TODO: Re-enable this if we implement proper dict-of-tables loop generation
+        # For now, return None to use scalar handling
         return None
 
+        # Original logic preserved below for reference:
+        # if not obj:
+        #     return None
+        #
+        # values = list(obj.values())
+        #
+        # # Check type homogeneity
+        # value_types = [type(v).__name__ for v in values]
+        # type_counts = Counter(value_types)
+        #
+        # if len(type_counts) != 1:
+        #     return None
+        #
+        # value_type = value_types[0]
+        #
+        # # Only interested in dict values for dict collections
+        # # (scalar-valued dicts stay as scalars)
+        # if value_type != "dict":
+        #     return None
+        #
+        # # Check structural homogeneity
+        # schema = self._analyze_dict_schema(values)
+        # if schema in ("simple_dict", "homogeneous"):
+        #     confidence = 0.9 if schema == "simple_dict" else 0.8
+        #
+        #     # Convert dict to list of items with 'key' added
+        #     items_with_keys = [{"_key": k, **v} for k, v in obj.items()]
+        #
+        #     return LoopCandidate(
+        #         path=path,
+        #         loop_var=self._derive_loop_var(path, singular=True),
+        #         items=items_with_keys,
+        #         item_schema="simple_dict",
+        #         confidence=confidence,
+        #     )
+        #
+        # return None
+
     def _analyze_dict_schema(
         self, dicts: list[dict[str, Any]]
     ) -> Literal["simple_dict", "homogeneous", "heterogeneous"]:
@@ -316,7 +342,7 @@ class LoopAnalyzer:
 
         XML is particularly suited for loops when we have repeated sibling elements.
         """
-        import xml.etree.ElementTree as ET
+        import xml.etree.ElementTree as ET  # nosec B405
 
         if not isinstance(root, ET.Element):
             return

tests/test_cli.py

@@ -1,10 +1,6 @@
 from __future__ import annotations
 
-import sys
 from pathlib import Path
-
-import pytest
-
 from jinjaturtle import cli
 
 SAMPLES_DIR = Path(__file__).parent / "samples"

tests/test_core_utils.py

@@ -168,8 +168,8 @@ def test_fallback_str_representer_for_unknown_type():
 
 def test_normalize_default_value_bool_inputs_are_stringified():
     """
-    Real boolean values should be turned into quoted 'true'/'false' strings
-    by _normalize_default_value via generate_ansible_yaml.
+    Boolean values are now preserved as booleans in YAML (not stringified).
+    This supports proper type preservation for JSON and other formats.
     """
     flat_items = [
         (("section", "flag_true"), True),
@@ -178,8 +178,9 @@ def test_normalize_default_value_bool_inputs_are_stringified():
     ansible_yaml = generate_ansible_yaml("role", flat_items)
     data = yaml.safe_load(ansible_yaml)
 
-    assert data["role_section_flag_true"] == "true"
-    assert data["role_section_flag_false"] == "false"
+    # Booleans are now preserved as booleans
+    assert data["role_section_flag_true"] is True
+    assert data["role_section_flag_false"] is False
 
 
 def test_flatten_config_unsupported_format():

tests/test_json_handler.py

@@ -2,7 +2,6 @@ from __future__ import annotations
 
 from pathlib import Path
 
-import json
 import pytest
 import yaml
 
@@ -10,6 +9,8 @@ from jinjaturtle.core import (
     parse_config,
     flatten_config,
     generate_ansible_yaml,
+    analyze_loops,
+    generate_jinja2_template,
 )
 from jinjaturtle.handlers.json import JsonHandler
 
@@ -23,30 +24,34 @@ def test_json_roundtrip():
     fmt, parsed = parse_config(json_path)
     assert fmt == "json"
 
-    flat_items = flatten_config(fmt, parsed)
-    ansible_yaml = generate_ansible_yaml("foobar", flat_items)
+    # With loop detection
+    loop_candidates = analyze_loops(fmt, parsed)
+    flat_items = flatten_config(fmt, parsed, loop_candidates)
+    ansible_yaml = generate_ansible_yaml("foobar", flat_items, loop_candidates)
     defaults = yaml.safe_load(ansible_yaml)
 
-    # Defaults: nested keys and list indices
+    # Defaults: nested keys
     assert defaults["foobar_foo"] == "bar"
     assert defaults["foobar_nested_a"] == 1
-    # Bool normalized to string "true"
-    assert defaults["foobar_nested_b"] == "true"
-    assert defaults["foobar_list_0"] == 10
-    assert defaults["foobar_list_1"] == 20
+    # Booleans are now preserved as booleans (not stringified)
+    assert defaults["foobar_nested_b"] is True
+    # List should be a list (not flattened to scalars)
+    assert defaults["foobar_list"] == [10, 20]
 
-    # Template generation is done via JsonHandler.generate_jinja2_template; we just
-    # make sure it produces a structure with the expected placeholders.
-    handler = JsonHandler()
-    templated = json.loads(
-        handler.generate_jinja2_template(parsed, role_prefix="foobar")
-    )
+    # Template generation with loops
+    template = generate_jinja2_template("json", parsed, "foobar", None, loop_candidates)
 
-    assert templated["foo"] == "{{ foobar_foo }}"
-    assert "foobar_nested_a" in str(templated)
-    assert "foobar_nested_b" in str(templated)
-    assert "foobar_list_0" in str(templated)
-    assert "foobar_list_1" in str(templated)
+    # Template should use | tojson for type preservation
+    assert "{{ foobar_foo | tojson }}" in template
+    assert "{{ foobar_nested_a | tojson }}" in template
+    assert "{{ foobar_nested_b | tojson }}" in template
+
+    # List should use loop (not scalar indices)
+    assert "{% for" in template
+    assert "foobar_list" in template
+    # Should NOT have scalar indices
+    assert "foobar_list_0" not in template
+    assert "foobar_list_1" not in template
 
 
 def test_generate_jinja2_template_json_type_error():

tests/test_roundtrip.py

@@ -0,0 +1,566 @@
+"""
+Roundtrip tests: Generate config → template/YAML → regenerate config → compare.
+
+These tests verify that:
+1. Generated Jinja2 template + Ansible YAML can reproduce the original config
+2. The regenerated config is semantically equivalent (allowing whitespace differences)
+3. No data loss occurs during the template generation process
+
+This is the ultimate validation - if the roundtrip works, the templates are correct.
+"""
+
+from __future__ import annotations
+
+import json
+import yaml
+from pathlib import Path
+from typing import Any
+from jinja2 import Environment, StrictUndefined
+
+import pytest
+
+from jinjaturtle.core import (
+    parse_config,
+    analyze_loops,
+    flatten_config,
+    generate_ansible_yaml,
+    generate_jinja2_template,
+)
+
+
+def render_template(template: str, variables: dict[str, Any]) -> str:
+    """Render a Jinja2 template with variables."""
+    env = Environment(undefined=StrictUndefined)
+    jinja_template = env.from_string(template)
+    return jinja_template.render(variables)
+
+
+class TestRoundtripJSON:
+    """Roundtrip tests for JSON files."""
+
+    def test_foo_json_roundtrip(self):
+        """Test foo.json can be perfectly regenerated from template."""
+        samples_dir = Path(__file__).parent / "samples"
+        json_file = samples_dir / "foo.json"
+
+        if not json_file.exists():
+            pytest.skip("foo.json not found")
+
+        # Read original
+        original_text = json_file.read_text()
+        original_data = json.loads(original_text)
+
+        # Generate template and YAML
+        fmt, parsed = parse_config(json_file)
+        loop_candidates = analyze_loops(fmt, parsed)
+        flat_items = flatten_config(fmt, parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(fmt, parsed, "test", None, loop_candidates)
+
+        # Load variables from YAML
+        variables = yaml.safe_load(ansible_yaml)
+
+        # Render template
+        regenerated_text = render_template(template, variables)
+        regenerated_data = json.loads(regenerated_text)
+
+        # Compare data structures (should match exactly)
+        assert regenerated_data == original_data, (
+            f"Regenerated JSON differs from original\n"
+            f"Original: {json.dumps(original_data, indent=2, sort_keys=True)}\n"
+            f"Regenerated: {json.dumps(regenerated_data, indent=2, sort_keys=True)}"
+        )
+
+    def test_json_all_types_roundtrip(self):
+        """Test JSON with all data types roundtrips perfectly."""
+        json_text = """
+        {
+          "string": "value",
+          "number": 42,
+          "float": 3.14,
+          "boolean": true,
+          "false_val": false,
+          "null_value": null,
+          "array": [1, 2, 3],
+          "object": {
+            "nested": "data"
+          }
+        }
+        """
+
+        original_data = json.loads(json_text)
+
+        # Generate template and YAML
+        loop_candidates = analyze_loops("json", original_data)
+        flat_items = flatten_config("json", original_data, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "json", original_data, "test", None, loop_candidates
+        )
+
+        # Render template
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+        regenerated_data = json.loads(regenerated_text)
+
+        # Should match exactly
+        assert regenerated_data == original_data
+
+
+class TestRoundtripYAML:
+    """Roundtrip tests for YAML files."""
+
+    def test_bar_yaml_roundtrip(self):
+        """Test bar.yaml can be regenerated from template."""
+        samples_dir = Path(__file__).parent / "samples"
+        yaml_file = samples_dir / "bar.yaml"
+
+        if not yaml_file.exists():
+            pytest.skip("bar.yaml not found")
+
+        # Read original
+        original_text = yaml_file.read_text()
+        original_data = yaml.safe_load(original_text)
+
+        # Generate template and YAML
+        fmt, parsed = parse_config(yaml_file)
+        loop_candidates = analyze_loops(fmt, parsed)
+        flat_items = flatten_config(fmt, parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            fmt, parsed, "test", original_text, loop_candidates
+        )
+
+        # Load variables from YAML
+        variables = yaml.safe_load(ansible_yaml)
+
+        # Render template
+        regenerated_text = render_template(template, variables)
+        regenerated_data = yaml.safe_load(regenerated_text)
+
+        # Compare data structures
+        assert regenerated_data == original_data, (
+            f"Regenerated YAML differs from original\n"
+            f"Original: {original_data}\n"
+            f"Regenerated: {regenerated_data}"
+        )
+
+    def test_yaml_with_lists_roundtrip(self):
+        """Test YAML with various list structures."""
+        yaml_text = """
+        name: myapp
+        simple_list:
+          - item1
+          - item2
+          - item3
+        list_of_dicts:
+          - name: first
+            value: 1
+          - name: second
+            value: 2
+        nested:
+          inner_list:
+            - a
+            - b
+        """
+
+        original_data = yaml.safe_load(yaml_text)
+
+        # Generate template and YAML
+        loop_candidates = analyze_loops("yaml", original_data)
+        flat_items = flatten_config("yaml", original_data, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "yaml", original_data, "test", yaml_text, loop_candidates
+        )
+
+        # Render template
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+        regenerated_data = yaml.safe_load(regenerated_text)
+
+        # Compare
+        assert regenerated_data == original_data
+
+
+class TestRoundtripTOML:
+    """Roundtrip tests for TOML files."""
+
+    def test_tom_toml_roundtrip(self):
+        """Test tom.toml can be regenerated from template."""
+        samples_dir = Path(__file__).parent / "samples"
+        toml_file = samples_dir / "tom.toml"
+
+        if not toml_file.exists():
+            pytest.skip("tom.toml not found")
+
+        # Read original
+        original_text = toml_file.read_text()
+        import tomllib
+
+        original_data = tomllib.loads(original_text)
+
+        # Generate template and YAML
+        fmt, parsed = parse_config(toml_file)
+        loop_candidates = analyze_loops(fmt, parsed)
+        flat_items = flatten_config(fmt, parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            fmt, parsed, "test", original_text, loop_candidates
+        )
+
+        # Load variables from YAML
+        variables = yaml.safe_load(ansible_yaml)
+
+        # Render template
+        regenerated_text = render_template(template, variables)
+        regenerated_data = tomllib.loads(regenerated_text)
+
+        # Compare data structures
+        # Note: TOML datetime objects need special handling
+        assert _compare_toml_data(regenerated_data, original_data), (
+            f"Regenerated TOML differs from original\n"
+            f"Original: {original_data}\n"
+            f"Regenerated: {regenerated_data}"
+        )
+
+    def test_toml_with_arrays_roundtrip(self):
+        """Test TOML with inline arrays and array-of-tables."""
+        toml_text = """
+        name = "test"
+        ports = [8080, 8081, 8082]
+        
+        [[database]]
+        host = "db1.example.com"
+        port = 5432
+        
+        [[database]]
+        host = "db2.example.com"
+        port = 5433
+        """
+
+        import tomllib
+
+        original_data = tomllib.loads(toml_text)
+
+        # Generate template and YAML
+        loop_candidates = analyze_loops("toml", original_data)
+        flat_items = flatten_config("toml", original_data, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "toml", original_data, "test", toml_text, loop_candidates
+        )
+
+        # Render template
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+        regenerated_data = tomllib.loads(regenerated_text)
+
+        # Compare
+        assert regenerated_data == original_data
+
+
+class TestRoundtripXML:
+    """Roundtrip tests for XML files."""
+
+    def test_xml_simple_roundtrip(self):
+        """Test simple XML can be regenerated."""
+        xml_text = """<?xml version="1.0"?>
+<config>
+  <name>test</name>
+  <port>8080</port>
+  <server>server1</server>
+  <server>server2</server>
+  <server>server3</server>
+</config>
+"""
+
+        import xml.etree.ElementTree as ET
+
+        original_root = ET.fromstring(xml_text)
+
+        # Generate template and YAML
+        fmt = "xml"
+        loop_candidates = analyze_loops(fmt, original_root)
+        flat_items = flatten_config(fmt, original_root, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            fmt, original_root, "test", xml_text, loop_candidates
+        )
+
+        # Render template
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+
+        # Parse regenerated XML
+        regenerated_root = ET.fromstring(regenerated_text)
+
+        # Compare XML structures (ignore insignificant whitespace)
+        assert _xml_elements_equal(
+            original_root, regenerated_root, ignore_whitespace=True
+        ), (
+            f"Regenerated XML differs from original\n"
+            f"Original: {ET.tostring(original_root, encoding='unicode')}\n"
+            f"Regenerated: {ET.tostring(regenerated_root, encoding='unicode')}"
+        )
+
+    def test_ossec_xml_roundtrip(self):
+        """Test ossec.xml (complex real-world XML) roundtrip."""
+        samples_dir = Path(__file__).parent / "samples"
+        xml_file = samples_dir / "ossec.xml"
+
+        if not xml_file.exists():
+            pytest.skip("ossec.xml not found")
+
+        # Read original
+        original_text = xml_file.read_text()
+        import xml.etree.ElementTree as ET
+
+        original_root = ET.fromstring(original_text)
+
+        # Generate template and YAML
+        fmt, parsed = parse_config(xml_file)
+        loop_candidates = analyze_loops(fmt, parsed)
+        flat_items = flatten_config(fmt, parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            fmt, parsed, "test", original_text, loop_candidates
+        )
+
+        # Load variables and render
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+
+        # Parse regenerated
+        regenerated_root = ET.fromstring(regenerated_text)
+
+        # Compare - for complex XML, we compare structure not exact text
+        assert _xml_elements_equal(
+            original_root, regenerated_root, ignore_whitespace=True
+        )
+
+
+class TestRoundtripINI:
+    """Roundtrip tests for INI files."""
+
+    def test_ini_simple_roundtrip(self):
+        """Test simple INI can be regenerated."""
+        ini_text = """[section1]
+key1 = value1
+key2 = value2
+
+[section2]
+key3 = value3
+"""
+
+        from configparser import ConfigParser
+
+        original_config = ConfigParser()
+        original_config.read_string(ini_text)
+
+        # Generate template and YAML
+        fmt = "ini"
+        loop_candidates = analyze_loops(fmt, original_config)
+        flat_items = flatten_config(fmt, original_config, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            fmt, original_config, "test", ini_text, loop_candidates
+        )
+
+        # Render template
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+
+        # Parse regenerated
+        regenerated_config = ConfigParser()
+        regenerated_config.read_string(regenerated_text)
+
+        # Compare
+        assert _ini_configs_equal(original_config, regenerated_config)
+
+
+class TestRoundtripEdgeCases:
+    """Roundtrip tests for edge cases and special scenarios."""
+
+    def test_empty_lists_roundtrip(self):
+        """Test handling of empty lists."""
+        json_text = '{"items": []}'
+        original_data = json.loads(json_text)
+
+        loop_candidates = analyze_loops("json", original_data)
+        flat_items = flatten_config("json", original_data, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "json", original_data, "test", None, loop_candidates
+        )
+
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+        regenerated_data = json.loads(regenerated_text)
+
+        assert regenerated_data == original_data
+
+    def test_special_characters_roundtrip(self):
+        """Test handling of special characters."""
+        json_data = {
+            "quote": 'He said "hello"',
+            "backslash": "path\\to\\file",
+            "newline": "line1\nline2",
+            "unicode": "emoji: 🚀",
+        }
+
+        loop_candidates = analyze_loops("json", json_data)
+        flat_items = flatten_config("json", json_data, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "json", json_data, "test", None, loop_candidates
+        )
+
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+        regenerated_data = json.loads(regenerated_text)
+
+        assert regenerated_data == json_data
+
+    def test_numeric_types_roundtrip(self):
+        """Test preservation of numeric types."""
+        json_data = {
+            "int": 42,
+            "float": 3.14159,
+            "negative": -100,
+            "zero": 0,
+            "large": 9999999999,
+        }
+
+        loop_candidates = analyze_loops("json", json_data)
+        flat_items = flatten_config("json", json_data, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "json", json_data, "test", None, loop_candidates
+        )
+
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+        regenerated_data = json.loads(regenerated_text)
+
+        assert regenerated_data == json_data
+
+    def test_boolean_preservation_roundtrip(self):
+        """Test that booleans are preserved correctly."""
+        yaml_text = """
+        enabled: true
+        disabled: false
+        """
+
+        original_data = yaml.safe_load(yaml_text)
+
+        loop_candidates = analyze_loops("yaml", original_data)
+        flat_items = flatten_config("yaml", original_data, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "yaml", original_data, "test", yaml_text, loop_candidates
+        )
+
+        variables = yaml.safe_load(ansible_yaml)
+        regenerated_text = render_template(template, variables)
+        regenerated_data = yaml.safe_load(regenerated_text)
+
+        # Both should be actual booleans
+        assert regenerated_data["enabled"] is True
+        assert regenerated_data["disabled"] is False
+
+
+# Helper functions
+
+
+def _compare_toml_data(data1: Any, data2: Any) -> bool:
+    """Compare TOML data, handling datetime objects."""
+    import datetime
+
+    if type(data1) != type(data2):
+        return False
+
+    if isinstance(data1, dict):
+        if set(data1.keys()) != set(data2.keys()):
+            return False
+        return all(_compare_toml_data(data1[k], data2[k]) for k in data1.keys())
+
+    elif isinstance(data1, list):
+        if len(data1) != len(data2):
+            return False
+        return all(_compare_toml_data(v1, v2) for v1, v2 in zip(data1, data2))
+
+    elif isinstance(data1, datetime.datetime):
+        # Compare datetime objects
+        return data1 == data2
+
+    else:
+        return data1 == data2
+
+
+def _xml_elements_equal(elem1, elem2, ignore_whitespace: bool = False) -> bool:
+    """Compare two XML elements for equality."""
+    # Compare tags
+    if elem1.tag != elem2.tag:
+        return False
+
+    # Compare attributes
+    if elem1.attrib != elem2.attrib:
+        return False
+
+    # Compare text
+    text1 = (elem1.text or "").strip() if ignore_whitespace else (elem1.text or "")
+    text2 = (elem2.text or "").strip() if ignore_whitespace else (elem2.text or "")
+    if text1 != text2:
+        return False
+
+    # Compare tail
+    tail1 = (elem1.tail or "").strip() if ignore_whitespace else (elem1.tail or "")
+    tail2 = (elem2.tail or "").strip() if ignore_whitespace else (elem2.tail or "")
+    if tail1 != tail2:
+        return False
+
+    # Compare children
+    children1 = list(elem1)
+    children2 = list(elem2)
+
+    if len(children1) != len(children2):
+        return False
+
+    return all(
+        _xml_elements_equal(c1, c2, ignore_whitespace)
+        for c1, c2 in zip(children1, children2)
+    )
+
+
+def _ini_configs_equal(config1, config2) -> bool:
+    """Compare two ConfigParser objects for equality."""
+    if set(config1.sections()) != set(config2.sections()):
+        return False
+
+    for section in config1.sections():
+        if set(config1.options(section)) != set(config2.options(section)):
+            return False
+
+        for option in config1.options(section):
+            if config1.get(section, option) != config2.get(section, option):
+                return False
+
+    return True
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])

tests/test_yaml_template_consistency.py

@@ -0,0 +1,558 @@
+"""
+Tests to ensure all Jinja2 template variables exist in the Ansible YAML.
+
+These tests catch the bug where templates reference variables that don't exist
+because the YAML has a list but the template uses scalar references (or vice versa).
+"""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+from typing import Set
+import yaml
+import pytest
+
+from jinjaturtle.core import (
+    parse_config,
+    analyze_loops,
+    flatten_config,
+    generate_ansible_yaml,
+    generate_jinja2_template,
+)
+
+
+def extract_jinja_variables(template: str) -> Set[str]:
+    """
+    Extract all Jinja2 variable names from a template that must exist in YAML.
+
+    Extracts variables from:
+    - {{ variable_name }}
+    - {{ variable.field }}
+    - {% for item in collection %}
+
+    Returns only the base variable names that must be defined in YAML.
+    Filters out loop variables (the 'item' part of 'for item in collection').
+    """
+    variables = set()
+
+    # First, find all loop variables (these are defined by the template, not YAML)
+    loop_vars = set()
+    for_pattern = r"\{%\s*for\s+(\w+)\s+in\s+([a-zA-Z_][a-zA-Z0-9_]*)"
+    for match in re.finditer(for_pattern, template):
+        loop_var = match.group(1)  # The item
+        collection = match.group(2)  # The collection
+        loop_vars.add(loop_var)
+        variables.add(collection)  # Collection must exist in YAML
+
+    # Pattern 1: {{ variable_name }} or {{ variable.field }}
+    # Captures the first part before any dots or filters
+    var_pattern = r"\{\{\s*([a-zA-Z_][a-zA-Z0-9_]*)"
+    for match in re.finditer(var_pattern, template):
+        var_name = match.group(1)
+        # Only add if it's not a loop variable
+        if var_name not in loop_vars:
+            variables.add(var_name)
+
+    return variables
+
+
+def extract_yaml_variables(ansible_yaml: str) -> Set[str]:
+    """
+    Extract all variable names from Ansible YAML.
+
+    Returns the top-level keys from the YAML document.
+    """
+    data = yaml.safe_load(ansible_yaml)
+    if not isinstance(data, dict):
+        return set()
+    return set(data.keys())
+
+
+class TestTemplateYamlConsistency:
+    """Tests that verify template variables exist in YAML."""
+
+    def test_simple_json_consistency(self):
+        """Simple JSON with scalars and lists."""
+        json_text = """
+        {
+          "name": "test",
+          "values": [1, 2, 3]
+        }
+        """
+
+        fmt = "json"
+        import json
+
+        parsed = json.loads(json_text)
+
+        loop_candidates = analyze_loops(fmt, parsed)
+        flat_items = flatten_config(fmt, parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(fmt, parsed, "app", None, loop_candidates)
+
+        yaml_vars = extract_yaml_variables(ansible_yaml)
+        template_vars = extract_jinja_variables(template)
+
+        # Every variable in template must exist in YAML
+        missing_vars = template_vars - yaml_vars
+        assert not missing_vars, (
+            f"Template references variables not in YAML: {missing_vars}\n"
+            f"YAML vars: {yaml_vars}\n"
+            f"Template vars: {template_vars}\n"
+            f"Template:\n{template}\n"
+            f"YAML:\n{ansible_yaml}"
+        )
+
+    def test_toml_inline_array_consistency(self):
+        """TOML with inline array should use loops consistently."""
+        import tomllib
+
+        toml_text = """
+        name = "myapp"
+        servers = ["server1", "server2", "server3"]
+        """
+
+        parsed = tomllib.loads(toml_text)
+        loop_candidates = analyze_loops("toml", parsed)
+        flat_items = flatten_config("toml", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "toml", parsed, "app", toml_text, loop_candidates
+        )
+
+        yaml_vars = extract_yaml_variables(ansible_yaml)
+        template_vars = extract_jinja_variables(template)
+
+        missing_vars = template_vars - yaml_vars
+        assert not missing_vars, (
+            f"Template references variables not in YAML: {missing_vars}\n"
+            f"Template:\n{template}\n"
+            f"YAML:\n{ansible_yaml}"
+        )
+
+    def test_toml_array_of_tables_consistency(self):
+        """TOML with [[array.of.tables]] should use loops consistently."""
+        import tomllib
+
+        toml_text = """
+        [[database]]
+        host = "db1.example.com"
+        port = 5432
+        
+        [[database]]
+        host = "db2.example.com"
+        port = 5433
+        """
+
+        parsed = tomllib.loads(toml_text)
+        loop_candidates = analyze_loops("toml", parsed)
+        flat_items = flatten_config("toml", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "toml", parsed, "app", toml_text, loop_candidates
+        )
+
+        yaml_vars = extract_yaml_variables(ansible_yaml)
+        template_vars = extract_jinja_variables(template)
+
+        missing_vars = template_vars - yaml_vars
+        assert not missing_vars, (
+            f"Template references variables not in YAML: {missing_vars}\n"
+            f"Template:\n{template}\n"
+            f"YAML:\n{ansible_yaml}"
+        )
+
+        # Additionally verify that if YAML has a list, template uses a loop
+        defaults = yaml.safe_load(ansible_yaml)
+        for var_name, value in defaults.items():
+            if isinstance(value, list) and len(value) > 1:
+                # YAML has a list - template should use {% for %}
+                assert "{% for" in template, (
+                    f"YAML has list variable '{var_name}' but template doesn't use loops\n"
+                    f"Template:\n{template}"
+                )
+
+    def test_yaml_list_consistency(self):
+        """YAML with lists should use loops consistently."""
+        yaml_text = """
+        name: myapp
+        servers:
+          - server1
+          - server2
+          - server3
+        databases:
+          - host: db1
+            port: 5432
+          - host: db2
+            port: 5433
+        """
+
+        parsed = yaml.safe_load(yaml_text)
+        loop_candidates = analyze_loops("yaml", parsed)
+        flat_items = flatten_config("yaml", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "yaml", parsed, "app", yaml_text, loop_candidates
+        )
+
+        yaml_vars = extract_yaml_variables(ansible_yaml)
+        template_vars = extract_jinja_variables(template)
+
+        missing_vars = template_vars - yaml_vars
+        assert not missing_vars, (
+            f"Template references variables not in YAML: {missing_vars}\n"
+            f"Template:\n{template}\n"
+            f"YAML:\n{ansible_yaml}"
+        )
+
+    def test_mixed_scalars_and_loops_consistency(self):
+        """Config with both scalars and loops should be consistent."""
+        import tomllib
+
+        toml_text = """
+        name = "myapp"
+        version = "1.0"
+        ports = [8080, 8081, 8082]
+        
+        [database]
+        host = "localhost"
+        port = 5432
+        
+        [[servers]]
+        name = "web1"
+        ip = "10.0.0.1"
+        
+        [[servers]]
+        name = "web2"
+        ip = "10.0.0.2"
+        """
+
+        parsed = tomllib.loads(toml_text)
+        loop_candidates = analyze_loops("toml", parsed)
+        flat_items = flatten_config("toml", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "toml", parsed, "app", toml_text, loop_candidates
+        )
+
+        yaml_vars = extract_yaml_variables(ansible_yaml)
+        template_vars = extract_jinja_variables(template)
+
+        missing_vars = template_vars - yaml_vars
+        assert not missing_vars, (
+            f"Template references variables not in YAML: {missing_vars}\n"
+            f"Template:\n{template}\n"
+            f"YAML:\n{ansible_yaml}"
+        )
+
+    def test_no_orphaned_scalar_references(self):
+        """
+        When YAML has a list variable, template must NOT reference scalar indices.
+
+        This catches the bug where:
+        - YAML has: app_list: [1, 2, 3]
+        - Template incorrectly uses: {{ app_list_0 }}, {{ app_list_1 }}
+        """
+        import json
+
+        json_text = '{"items": [1, 2, 3, 4, 5]}'
+        parsed = json.loads(json_text)
+
+        loop_candidates = analyze_loops("json", parsed)
+        flat_items = flatten_config("json", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "json", parsed, "app", None, loop_candidates
+        )
+
+        defaults = yaml.safe_load(ansible_yaml)
+
+        # Check each list variable in YAML
+        for var_name, value in defaults.items():
+            if isinstance(value, list):
+                # Template should NOT reference app_items_0, app_items_1, etc.
+                for i in range(len(value)):
+                    scalar_ref = f"{var_name}_{i}"
+                    assert scalar_ref not in template, (
+                        f"Template incorrectly uses scalar reference '{scalar_ref}' "
+                        f"when YAML has '{var_name}' as a list\n"
+                        f"Template should use loops, not scalar indices\n"
+                        f"Template:\n{template}"
+                    )
+
+    def test_all_sample_files_consistency(self):
+        """Test all sample files for consistency."""
+        samples_dir = Path(__file__).parent / "samples"
+
+        sample_files = [
+            ("foo.json", "json"),
+            ("bar.yaml", "yaml"),
+            ("tom.toml", "toml"),
+        ]
+
+        for filename, fmt in sample_files:
+            file_path = samples_dir / filename
+            if not file_path.exists():
+                pytest.skip(f"Sample file {filename} not found")
+
+            original_text = file_path.read_text()
+            fmt_detected, parsed = parse_config(file_path)
+
+            loop_candidates = analyze_loops(fmt_detected, parsed)
+            flat_items = flatten_config(fmt_detected, parsed, loop_candidates)
+
+            ansible_yaml = generate_ansible_yaml("test", flat_items, loop_candidates)
+            template = generate_jinja2_template(
+                fmt_detected, parsed, "test", original_text, loop_candidates
+            )
+
+            yaml_vars = extract_yaml_variables(ansible_yaml)
+            template_vars = extract_jinja_variables(template)
+
+            missing_vars = template_vars - yaml_vars
+            assert not missing_vars, (
+                f"File: {filename}\n"
+                f"Template references variables not in YAML: {missing_vars}\n"
+                f"YAML vars: {yaml_vars}\n"
+                f"Template vars: {template_vars}\n"
+                f"Template:\n{template}\n"
+                f"YAML:\n{ansible_yaml}"
+            )
+
+
+class TestStructuralConsistency:
+    """Tests that verify structural consistency between YAML and templates."""
+
+    def test_list_in_yaml_means_loop_in_template(self):
+        """When YAML has a list (len > 1), template should use {% for %}."""
+        import json
+
+        json_text = """
+        {
+          "scalar": "value",
+          "list": [1, 2, 3]
+        }
+        """
+
+        parsed = json.loads(json_text)
+        loop_candidates = analyze_loops("json", parsed)
+        flat_items = flatten_config("json", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "json", parsed, "app", None, loop_candidates
+        )
+
+        defaults = yaml.safe_load(ansible_yaml)
+
+        # Find list variables in YAML
+        list_vars = [
+            k for k, v in defaults.items() if isinstance(v, list) and len(v) > 1
+        ]
+
+        if list_vars:
+            # Template must contain for loops
+            assert "{% for" in template, (
+                f"YAML has list variables {list_vars} but template has no loops\n"
+                f"Template:\n{template}"
+            )
+
+            # Each list variable should be used in a for loop
+            for var_name in list_vars:
+                # Look for "{% for ... in var_name %}"
+                for_pattern = (
+                    r"\{%\s*for\s+\w+\s+in\s+" + re.escape(var_name) + r"\s*%\}"
+                )
+                assert re.search(for_pattern, template), (
+                    f"List variable '{var_name}' not used in a for loop\n"
+                    f"Template:\n{template}"
+                )
+
+    def test_scalar_in_yaml_means_no_loop_in_template(self):
+        """When YAML has scalars, template should use {{ var }}, not loops."""
+        import json
+
+        json_text = """
+        {
+          "name": "test",
+          "port": 8080,
+          "enabled": true
+        }
+        """
+
+        parsed = json.loads(json_text)
+        loop_candidates = analyze_loops("json", parsed)
+        flat_items = flatten_config("json", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "json", parsed, "app", None, loop_candidates
+        )
+
+        defaults = yaml.safe_load(ansible_yaml)
+
+        # All variables are scalars - template should NOT have loops
+        scalar_vars = [
+            k for k, v in defaults.items() if not isinstance(v, (list, dict))
+        ]
+
+        # Check that scalar vars are used directly, not in loops
+        for var_name in scalar_vars:
+            # Should appear in {{ var_name }}, not {% for ... in var_name %}
+            direct_ref = f"{{{{ {var_name}"
+            loop_ref = f"for .* in {var_name}"
+
+            assert direct_ref in template, (
+                f"Scalar variable '{var_name}' should be directly referenced\n"
+                f"Template:\n{template}"
+            )
+
+            assert not re.search(loop_ref, template), (
+                f"Scalar variable '{var_name}' incorrectly used in a loop\n"
+                f"Template:\n{template}"
+            )
+
+    def test_no_undefined_variable_errors(self):
+        """
+        Simulate Ansible template rendering to catch undefined variables.
+
+        This is the ultimate test - actually render the template with the YAML
+        and verify no undefined variable errors occur.
+        """
+        from jinja2 import Environment, StrictUndefined
+        import json
+
+        json_text = """
+        {
+          "name": "myapp",
+          "servers": ["web1", "web2"],
+          "database": {
+            "host": "localhost",
+            "port": 5432
+          }
+        }
+        """
+
+        parsed = json.loads(json_text)
+        loop_candidates = analyze_loops("json", parsed)
+        flat_items = flatten_config("json", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "json", parsed, "app", None, loop_candidates
+        )
+
+        # Load variables from YAML
+        variables = yaml.safe_load(ansible_yaml)
+
+        # Try to render the template
+        env = Environment(undefined=StrictUndefined)
+        try:
+            jinja_template = env.from_string(template)
+            rendered = jinja_template.render(variables)
+
+            # Successfully rendered - this is what we want!
+            assert rendered, "Template rendered successfully"
+
+        except Exception as e:
+            pytest.fail(
+                f"Template rendering failed with variables from YAML\n"
+                f"Error: {e}\n"
+                f"Template:\n{template}\n"
+                f"Variables:\n{ansible_yaml}"
+            )
+
+
+class TestRegressionBugs:
+    """Tests for specific bugs that were found and fixed."""
+
+    def test_toml_array_of_tables_no_scalar_refs(self):
+        """
+        Regression test: TOML [[array]] should not generate scalar references.
+
+        Bug: Template had {{ app_database_host }} when YAML had app_database as list.
+        """
+        import tomllib
+
+        toml_text = """
+        [[database]]
+        host = "db1"
+        port = 5432
+        
+        [[database]]
+        host = "db2"
+        port = 5433
+        """
+
+        parsed = tomllib.loads(toml_text)
+        loop_candidates = analyze_loops("toml", parsed)
+        flat_items = flatten_config("toml", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "toml", parsed, "app", toml_text, loop_candidates
+        )
+
+        # YAML should have app_database as a list
+        defaults = yaml.safe_load(ansible_yaml)
+        assert isinstance(
+            defaults.get("app_database"), list
+        ), f"Expected app_database to be a list in YAML\n{ansible_yaml}"
+
+        # Template should NOT have app_database_host or app_database_port
+        assert (
+            "app_database_host" not in template
+        ), f"Template incorrectly uses scalar 'app_database_host'\n{template}"
+        assert (
+            "app_database_port" not in template
+        ), f"Template incorrectly uses scalar 'app_database_port'\n{template}"
+
+        # Template SHOULD use a loop
+        assert "{% for" in template, f"Template should use a loop\n{template}"
+        assert (
+            "app_database" in template
+        ), f"Template should reference app_database\n{template}"
+
+    def test_json_array_no_index_refs(self):
+        """
+        Regression test: JSON arrays should not generate index references.
+
+        Bug: Template had {{ app_list_0 }}, {{ app_list_1 }} when YAML had app_list as list.
+        """
+        import json
+
+        json_text = '{"items": [1, 2, 3]}'
+        parsed = json.loads(json_text)
+
+        loop_candidates = analyze_loops("json", parsed)
+        flat_items = flatten_config("json", parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            "json", parsed, "app", None, loop_candidates
+        )
+
+        # YAML should have app_items as a list
+        defaults = yaml.safe_load(ansible_yaml)
+        assert isinstance(defaults.get("app_items"), list)
+
+        # Template should NOT have app_items_0, app_items_1, app_items_2
+        for i in range(3):
+            assert (
+                f"app_items_{i}" not in template
+            ), f"Template incorrectly uses scalar 'app_items_{i}'\n{template}"
+
+        # Template SHOULD use a loop
+        assert "{% for" in template
+        assert "app_items" in template
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])

utils/diff_configs.py

@@ -0,0 +1,216 @@
+#!/usr/bin/env python3
+"""
+Side-by-side comparison of original vs regenerated config.
+
+Usage:
+    ./diff_configs.py tests/samples/foo.json
+    ./diff_configs.py tests/samples/tom.toml --context 5
+"""
+
+import argparse
+import sys
+from pathlib import Path
+import difflib
+import yaml
+from jinja2 import Environment, StrictUndefined
+
+# Add parent directory to path for imports
+sys.path.insert(0, str(Path(__file__).parent))
+
+from jinjaturtle.core import (
+    parse_config,
+    analyze_loops,
+    flatten_config,
+    generate_ansible_yaml,
+    generate_jinja2_template,
+)
+
+
+def colorize(text: str, color: str) -> str:
+    """Add ANSI color codes."""
+    colors = {
+        "red": "\033[91m",
+        "green": "\033[92m",
+        "yellow": "\033[93m",
+        "blue": "\033[94m",
+        "reset": "\033[0m",
+    }
+    return f"{colors.get(color, '')}{text}{colors['reset']}"
+
+
+def side_by_side_diff(original: str, regenerated: str, width: int = 80):
+    """Print side-by-side diff."""
+    orig_lines = original.splitlines()
+    regen_lines = regenerated.splitlines()
+
+    # Calculate column width
+    col_width = width // 2 - 3
+
+    print(
+        colorize("ORIGINAL".center(col_width), "blue")
+        + " | "
+        + colorize("REGENERATED".center(col_width), "green")
+    )
+    print("-" * col_width + "-+-" + "-" * col_width)
+
+    max_lines = max(len(orig_lines), len(regen_lines))
+
+    for i in range(max_lines):
+        orig_line = orig_lines[i] if i < len(orig_lines) else ""
+        regen_line = regen_lines[i] if i < len(regen_lines) else ""
+
+        # Truncate if too long
+        if len(orig_line) > col_width - 2:
+            orig_line = orig_line[: col_width - 5] + "..."
+        if len(regen_line) > col_width - 2:
+            regen_line = regen_line[: col_width - 5] + "..."
+
+        # Color lines if different
+        if orig_line != regen_line:
+            orig_display = colorize(orig_line.ljust(col_width), "red")
+            regen_display = colorize(regen_line.ljust(col_width), "green")
+        else:
+            orig_display = orig_line.ljust(col_width)
+            regen_display = regen_line.ljust(col_width)
+
+        print(f"{orig_display} | {regen_display}")
+
+
+def unified_diff(original: str, regenerated: str, filename: str, context: int = 3):
+    """Print unified diff."""
+    orig_lines = original.splitlines(keepends=True)
+    regen_lines = regenerated.splitlines(keepends=True)
+
+    diff = difflib.unified_diff(
+        orig_lines,
+        regen_lines,
+        fromfile=f"{filename} (original)",
+        tofile=f"{filename} (regenerated)",
+        n=context,
+    )
+
+    for line in diff:
+        if line.startswith("+++") or line.startswith("---"):
+            print(colorize(line.rstrip(), "blue"))
+        elif line.startswith("@@"):
+            print(colorize(line.rstrip(), "cyan"))
+        elif line.startswith("+"):
+            print(colorize(line.rstrip(), "green"))
+        elif line.startswith("-"):
+            print(colorize(line.rstrip(), "red"))
+        else:
+            print(line.rstrip())
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Compare original config with regenerated version",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+    )
+
+    parser.add_argument("file", type=Path, help="Config file to check")
+
+    parser.add_argument(
+        "--mode",
+        choices=["side-by-side", "unified", "both"],
+        default="both",
+        help="Comparison mode (default: both)",
+    )
+
+    parser.add_argument(
+        "--context",
+        type=int,
+        default=3,
+        help="Number of context lines for unified diff (default: 3)",
+    )
+
+    parser.add_argument(
+        "--width",
+        type=int,
+        default=160,
+        help="Terminal width for side-by-side (default: 160)",
+    )
+
+    args = parser.parse_args()
+
+    if not args.file.exists():
+        print(colorize(f"❌ File not found: {args.file}", "red"))
+        return 1
+
+    print(colorize(f"\n{'=' * 80}", "blue"))
+    print(colorize(f"  Comparing: {args.file}", "blue"))
+    print(colorize(f"{'=' * 80}\n", "blue"))
+
+    # Read and regenerate
+    try:
+        original_text = args.file.read_text()
+
+        fmt, parsed = parse_config(args.file)
+        loop_candidates = analyze_loops(fmt, parsed)
+        flat_items = flatten_config(fmt, parsed, loop_candidates)
+
+        ansible_yaml = generate_ansible_yaml("app", flat_items, loop_candidates)
+        template = generate_jinja2_template(
+            fmt, parsed, "app", original_text, loop_candidates
+        )
+
+        variables = yaml.safe_load(ansible_yaml)
+        env = Environment(undefined=StrictUndefined)
+        jinja_template = env.from_string(template)
+        regenerated_text = jinja_template.render(variables)
+
+        # Check if identical
+        if original_text.strip() == regenerated_text.strip():
+            print(colorize("✅ Files are IDENTICAL (text comparison)\n", "green"))
+        else:
+            # Show diff
+            if args.mode in ("unified", "both"):
+                print(colorize("\n--- UNIFIED DIFF ---\n", "yellow"))
+                unified_diff(
+                    original_text, regenerated_text, args.file.name, args.context
+                )
+
+            if args.mode in ("side-by-side", "both"):
+                print(colorize("\n--- SIDE-BY-SIDE COMPARISON ---\n", "yellow"))
+                side_by_side_diff(original_text, regenerated_text, args.width)
+
+        # Try semantic comparison
+        print(colorize(f"\n{'=' * 80}", "cyan"))
+        print(colorize("  Semantic Comparison", "cyan"))
+        print(colorize(f"{'=' * 80}", "cyan"))
+
+        try:
+            if fmt == "json":
+                import json
+
+                if json.loads(original_text) == json.loads(regenerated_text):
+                    print(colorize("✅ JSON data structures are IDENTICAL", "green"))
+                else:
+                    print(colorize("⚠️  JSON data structures DIFFER", "yellow"))
+            elif fmt == "yaml":
+                if yaml.safe_load(original_text) == yaml.safe_load(regenerated_text):
+                    print(colorize("✅ YAML data structures are IDENTICAL", "green"))
+                else:
+                    print(colorize("⚠️  YAML data structures DIFFER", "yellow"))
+            elif fmt == "toml":
+                import tomllib
+
+                if tomllib.loads(original_text) == tomllib.loads(regenerated_text):
+                    print(colorize("✅ TOML data structures are IDENTICAL", "green"))
+                else:
+                    print(colorize("⚠️  TOML data structures DIFFER", "yellow"))
+        except Exception as e:
+            print(colorize(f"ℹ️  Could not compare semantically: {e}", "yellow"))
+
+    except Exception as e:
+        print(colorize(f"❌ ERROR: {e}", "red"))
+        import traceback
+
+        traceback.print_exc()
+        return 1
+
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

utils/regenerate.py

@@ -0,0 +1,162 @@
+#!/usr/bin/env python3
+"""
+Regenerate config files and save all intermediate files.
+
+Creates:
+  - original.{ext}
+  - defaults/main.yml
+  - templates/config.j2
+  - regenerated.{ext}
+
+Usage:
+    ./regenerate.py tests/samples/foo.json
+    ./regenerate.py tests/samples/tom.toml --output-dir tmp/toml_test
+"""
+
+import argparse
+import sys
+from pathlib import Path
+import yaml
+from jinja2 import Environment, StrictUndefined
+
+# Add parent directory to path for imports
+sys.path.insert(0, str(Path(__file__).parent))
+
+from jinjaturtle.core import (
+    parse_config,
+    analyze_loops,
+    flatten_config,
+    generate_ansible_yaml,
+    generate_jinja2_template,
+)
+
+
+def regenerate_and_save(config_file: Path, output_dir: Path, role_prefix: str = "app"):
+    """
+    Regenerate config and save all intermediate files.
+    """
+    output_dir.mkdir(parents=True, exist_ok=True)
+
+    # Read original
+    original_text = config_file.read_text()
+    fmt, parsed = parse_config(config_file)
+
+    # Determine extension
+    ext = config_file.suffix
+
+    # Save original
+    original_out = output_dir / f"original{ext}"
+    original_out.write_text(original_text)
+    print(f"📄 Saved: {original_out}")
+
+    # Generate Ansible files
+    loop_candidates = analyze_loops(fmt, parsed)
+    flat_items = flatten_config(fmt, parsed, loop_candidates)
+
+    ansible_yaml = generate_ansible_yaml(role_prefix, flat_items, loop_candidates)
+    template = generate_jinja2_template(
+        fmt, parsed, role_prefix, original_text, loop_candidates
+    )
+
+    # Save Ansible YAML
+    defaults_dir = output_dir / "defaults"
+    defaults_dir.mkdir(exist_ok=True)
+    defaults_file = defaults_dir / "main.yml"
+    defaults_file.write_text(ansible_yaml)
+    print(f"📄 Saved: {defaults_file}")
+
+    # Save template
+    templates_dir = output_dir / "templates"
+    templates_dir.mkdir(exist_ok=True)
+    template_file = templates_dir / "config.j2"
+    template_file.write_text(template)
+    print(f"📄 Saved: {template_file}")
+
+    # Render template
+    variables = yaml.safe_load(ansible_yaml)
+    env = Environment(undefined=StrictUndefined)
+    jinja_template = env.from_string(template)
+    regenerated_text = jinja_template.render(variables)
+
+    # Save regenerated
+    regenerated_out = output_dir / f"regenerated{ext}"
+    regenerated_out.write_text(regenerated_text)
+    print(f"📄 Saved: {regenerated_out}")
+
+    # Summary
+    print(f"\n✅ All files saved to: {output_dir}")
+    print("\n📊 Statistics:")
+    print(f"   Format: {fmt}")
+    print(f"   Loop candidates: {len(loop_candidates)}")
+    if loop_candidates:
+        print("   Loops detected:")
+        for c in loop_candidates:
+            print(f"     - {'.'.join(c.path)}: {len(c.items)} items")
+
+    # Check if identical
+    if original_text.strip() == regenerated_text.strip():
+        print("\n✅ Original and regenerated are IDENTICAL (text comparison)")
+    else:
+        print("\n⚠️  Original and regenerated differ in whitespace/formatting")
+        print(f"   Run: diff {original_out} {regenerated_out}")
+
+    return output_dir
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Regenerate config and save all intermediate files",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        epilog="""
+Examples:
+  %(prog)s tests/samples/foo.json
+  %(prog)s tests/samples/tom.toml -o tmp/toml_output
+  %(prog)s tests/samples/bar.yaml --role-prefix myapp
+        """,
+    )
+
+    parser.add_argument("file", type=Path, help="Config file to process")
+
+    parser.add_argument(
+        "-o",
+        "--output-dir",
+        type=Path,
+        help="Output directory (default: regenerated_<filename>)",
+    )
+
+    parser.add_argument(
+        "-r",
+        "--role-prefix",
+        default="app",
+        help="Ansible role prefix for variables (default: app)",
+    )
+
+    args = parser.parse_args()
+
+    if not args.file.exists():
+        print(f"❌ File not found: {args.file}")
+        return 1
+
+    # Determine output directory
+    if args.output_dir:
+        output_dir = args.output_dir
+    else:
+        output_dir = Path(f"regenerated_{args.file.stem}")
+
+    print(f"🔄 Regenerating: {args.file}")
+    print(f"📁 Output directory: {output_dir}")
+    print(f"🏷️  Role prefix: {args.role_prefix}\n")
+
+    try:
+        regenerate_and_save(args.file, output_dir, args.role_prefix)
+        return 0
+    except Exception as e:
+        print(f"\n❌ ERROR: {e}")
+        import traceback
+
+        traceback.print_exc()
+        return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())