Initial commit

src/cspresso/ensure_playwright.py

@@ -0,0 +1,115 @@
+from __future__ import annotations
+
+import os
+import sys
+import time
+import subprocess
+from dataclasses import dataclass
+from pathlib import Path
+
+from playwright.async_api import async_playwright, Error as PlaywrightError
+
+
+@dataclass(frozen=True)
+class EnsureResult:
+    browsers_path: Path
+    installed: bool
+
+
+def _default_browsers_path() -> Path:
+    # Project-local by default. Override with PLAYWRIGHT_BROWSERS_PATH or CLI flag.
+    return Path(__file__).resolve().parents[2] / ".pw-browsers"
+
+
+def _env_with_browsers_path(browsers_path: Path) -> dict[str, str]:
+    env = os.environ.copy()
+    env["PLAYWRIGHT_BROWSERS_PATH"] = str(browsers_path)
+    return env
+
+
+def _acquire_install_lock(
+    lock_path: Path, timeout_s: float = 120.0, poll_s: float = 0.2
+) -> None:
+    """Very small cross-platform lock using atomic file creation.
+    Avoids concurrent Playwright installs when multiple processes start at once.
+
+    Not perfect, but good enough for most CLI usage.
+    """
+    start = time.time()
+    while True:
+        try:
+            fd = os.open(str(lock_path), os.O_CREAT | os.O_EXCL | os.O_WRONLY)
+            os.close(fd)
+            return
+        except FileExistsError:
+            if time.time() - start > timeout_s:
+                raise TimeoutError(f"Timed out waiting for install lock: {lock_path}")
+            time.sleep(poll_s)
+
+
+def _release_install_lock(lock_path: Path) -> None:
+    try:
+        lock_path.unlink(missing_ok=True)  # Python 3.8+
+    except Exception:
+        pass
+
+
+def _install_chromium(browsers_path: Path, with_deps: bool = False) -> None:
+    env = _env_with_browsers_path(browsers_path)
+    cmd = [sys.executable, "-m", "playwright", "install"]
+    if with_deps:
+        cmd.append("--with-deps")
+    cmd.append("chromium")
+
+    subprocess.run(cmd, check=True, env=env)
+
+
+async def _can_launch_chromium(browsers_path: Path) -> bool:
+    # Ensure this process uses the same path too.
+    os.environ["PLAYWRIGHT_BROWSERS_PATH"] = str(browsers_path)
+    try:
+        async with async_playwright() as p:
+            browser = await p.chromium.launch(headless=True)
+            await browser.close()
+        return True
+    except PlaywrightError:
+        return False
+
+
+async def ensure_chromium_installed(
+    browsers_path: Path | None = None,
+    *,
+    with_deps: bool = False,
+    lock_timeout_s: float = 120.0,
+) -> EnsureResult:
+    """Ensure Playwright's Chromium is installed and launchable.
+
+    Strategy:
+    - Attempt a tiny headless launch.
+    - If it fails, acquire a lock and run `python -m playwright install chromium` (optionally --with-deps).
+    - Retry launch once.
+    """
+    bp = browsers_path or _default_browsers_path()
+    bp.mkdir(parents=True, exist_ok=True)
+
+    if await _can_launch_chromium(bp):
+        return EnsureResult(browsers_path=bp, installed=False)
+
+    lock_path = bp / ".install.lock"
+    _acquire_install_lock(lock_path, timeout_s=lock_timeout_s)
+    try:
+        # Another process might have installed while we waited; check again.
+        if await _can_launch_chromium(bp):
+            return EnsureResult(browsers_path=bp, installed=False)
+
+        _install_chromium(bp, with_deps=with_deps)
+
+        if not await _can_launch_chromium(bp):
+            raise RuntimeError(
+                "Playwright Chromium install completed, but Chromium still failed to launch. "
+                "On Linux, you may need additional system dependencies."
+            )
+
+        return EnsureResult(browsers_path=bp, installed=True)
+    finally:
+        _release_install_lock(lock_path)