All providers: make managed shim refresh idempotent

Brew / Npm / Pnpm / Goget providers all refreshed their managed
``bin_dir`` shim on every ``default_abspath_handler`` call (i.e. every
``load()``) by unconditionally ``unlink`` + ``symlink_to``. Even for
symlinks -- where ``.resolve().stat()`` follows the link and returns
the target's stable mtime -- this still churns the shim's inode on
every load, which invalidates fingerprint caches keyed on inode and
causes unnecessary filesystem thrash in tight lifecycle loops.

Skip the unlink + rewrite when the existing symlink already resolves
to ``target``. Matches the idempotency check already present in the
base class ``_link_loaded_binary`` and the same fix just applied to
Puppeteer/Playwright ``_refresh_symlink``.

Author: claude

abxpkg/binprovider_brew.py

@@ -183,6 +183,15 @@ def _refresh_bin_link(
                 except Exception:
                     break
                 walk_path = walk_path.parent
+        # Idempotent refresh: skip when shim already points at target.
+        # Rewriting on every load() bumps mtime and churns the inode,
+        # which invalidates fingerprint caches unnecessarily.
+        if link_path.is_symlink():
+            try:
+                if link_path.readlink() == Path(target):
+                    return TypeAdapter(HostBinPath).validate_python(link_path)
+            except OSError:
+                pass
         if link_path.exists() or link_path.is_symlink():
             link_path.unlink(missing_ok=True)
         link_path.symlink_to(target)

abxpkg/binprovider_goget.py

@@ -294,6 +294,15 @@ def default_abspath_handler(
         assert bin_dir is not None
         link_path = bin_dir / str(bin_name)
         link_path.parent.mkdir(parents=True, exist_ok=True)
+        # Idempotent refresh: skip when shim already points at target.
+        # Rewriting on every load() bumps mtime and churns the inode,
+        # which invalidates fingerprint caches unnecessarily.
+        if link_path.is_symlink():
+            try:
+                if link_path.readlink() == Path(direct_abspath):
+                    return TypeAdapter(HostBinPath).validate_python(link_path)
+            except OSError:
+                pass
         if link_path.exists() or link_path.is_symlink():
             link_path.unlink(missing_ok=True)
         link_path.symlink_to(direct_abspath)

abxpkg/binprovider_npm.py

@@ -377,6 +377,15 @@ def _refresh_bin_link(
         link_path = self._linked_bin_path(bin_name)
         assert link_path is not None, "_refresh_bin_link requires bin_dir to be set"
         link_path.parent.mkdir(parents=True, exist_ok=True)
+        # Idempotent refresh: skip when shim already points at target.
+        # Rewriting on every load() bumps mtime and churns the inode,
+        # which invalidates fingerprint caches unnecessarily.
+        if link_path.is_symlink():
+            try:
+                if link_path.readlink() == Path(target):
+                    return TypeAdapter(HostBinPath).validate_python(link_path)
+            except OSError:
+                pass
         if link_path.exists() or link_path.is_symlink():
             link_path.unlink(missing_ok=True)
         link_path.symlink_to(target)

abxpkg/binprovider_pnpm.py

@@ -274,6 +274,15 @@ def _refresh_bin_link(
         link_path = self._linked_bin_path(bin_name)
         assert link_path is not None, "_refresh_bin_link requires bin_dir to be set"
         link_path.parent.mkdir(parents=True, exist_ok=True)
+        # Idempotent refresh: skip when shim already points at target.
+        # Rewriting on every load() bumps mtime and churns the inode,
+        # which invalidates fingerprint caches unnecessarily.
+        if link_path.is_symlink():
+            try:
+                if link_path.readlink() == Path(target):
+                    return TypeAdapter(HostBinPath).validate_python(link_path)
+            except OSError:
+                pass
         if link_path.exists() or link_path.is_symlink():
             link_path.unlink(missing_ok=True)
         link_path.symlink_to(target)