Puppeteer/Playwright _refresh_symlink: idempotent when shim already matches

On macOS, chrome/chromium ship as ``.app`` bundles so the managed
``bin_dir`` shim is a shell-script launcher (``#!/bin/sh\nexec <path>``),
not a symlink. ``default_abspath_handler`` calls ``_refresh_symlink`` on
every ``load()``, which unconditionally deleted + rewrote the shim --
bumping its mtime each time. Tests that call ``install()`` then
``assert_shallow_binary_loaded`` (which re-stats the shim via
``get_abspath(no_cache=True)``) then observed ``loaded_mtime !=
resolved.stat().st_mtime_ns``, failing across every macOS puppeteer/
playwright test (8 playwright tests + test_chrome_alias in puppeteer).

Linux uses a real symlink and ``.resolve().stat()`` follows it to the
browser binary, whose mtime is stable -- so Linux CI was already green.

Skip the unlink+rewrite when the existing shim already points at
``target`` (symlink target equals path, or shell-script contents match
what we'd write). ``install()`` still always resolves the fresh path,
and a stale shim pointing at an old target still gets replaced.

Author: claude

abxpkg/binprovider_playwright.py

@@ -561,16 +561,36 @@ def _refresh_symlink(self, bin_name: str, target: Path) -> Path:
         )
         link = self.bin_dir / bin_name
         link.parent.mkdir(parents=True, exist_ok=True)
-        if link.exists() or link.is_symlink():
-            link.unlink(missing_ok=True)
         # On macOS the executable is buried inside a ``.app`` bundle, so
         # write a tiny shell shim instead of a symlink (same pattern as
         # PuppeteerProvider).
-        if os.name == "posix" and ".app/Contents/MacOS/" in str(target):
-            link.write_text(
-                f'#!/bin/sh\nexec {shlex.quote(str(target))} "$@"\n',
-                encoding="utf-8",
-            )
+        use_shell_shim = os.name == "posix" and ".app/Contents/MacOS/" in str(target)
+        desired_script = (
+            f'#!/bin/sh\nexec {shlex.quote(str(target))} "$@"\n'
+            if use_shell_shim
+            else None
+        )
+        # Idempotent refresh: leave the shim untouched when it already
+        # points at ``target``. Rewriting on every ``load()`` would bump
+        # the shim's mtime (shell-script case), which breaks callers
+        # that stat the shim to validate a freshly-installed binary.
+        if link.is_symlink():
+            try:
+                if os.readlink(link) == str(target):
+                    return link
+            except OSError:
+                pass
+        elif use_shell_shim and link.is_file():
+            try:
+                if link.read_text(encoding="utf-8") == desired_script:
+                    return link
+            except OSError:
+                pass
+        if link.exists() or link.is_symlink():
+            link.unlink(missing_ok=True)
+        if use_shell_shim:
+            assert desired_script is not None
+            link.write_text(desired_script, encoding="utf-8")
             link.chmod(0o755)
             return link
         link.symlink_to(target)

abxpkg/binprovider_puppeteer.py

@@ -491,13 +491,33 @@ def _refresh_symlink(self, bin_name: str, target: Path) -> Path:
         assert bin_dir is not None
         link_path = bin_dir / bin_name
         link_path.parent.mkdir(parents=True, exist_ok=True)
+        use_shell_shim = os.name == "posix" and ".app/Contents/MacOS/" in str(target)
+        desired_script = (
+            f'#!/bin/sh\nexec {shlex.quote(str(target))} "$@"\n'
+            if use_shell_shim
+            else None
+        )
+        # Idempotent refresh: leave the shim untouched when it already
+        # points at ``target``. Rewriting on every ``load()`` would bump
+        # the shim's mtime (shell-script case), which breaks callers
+        # that stat the shim to validate a freshly-installed binary.
+        if link_path.is_symlink():
+            try:
+                if os.readlink(link_path) == str(target):
+                    return link_path
+            except OSError:
+                pass
+        elif use_shell_shim and link_path.is_file():
+            try:
+                if link_path.read_text(encoding="utf-8") == desired_script:
+                    return link_path
+            except OSError:
+                pass
         if link_path.exists() or link_path.is_symlink():
             link_path.unlink(missing_ok=True)
-        if os.name == "posix" and ".app/Contents/MacOS/" in str(target):
-            link_path.write_text(
-                f'#!/bin/sh\nexec {shlex.quote(str(target))} "$@"\n',
-                encoding="utf-8",
-            )
+        if use_shell_shim:
+            assert desired_script is not None
+            link_path.write_text(desired_script, encoding="utf-8")
             link_path.chmod(0o755)
             return link_path
         link_path.symlink_to(target)