fix: backport #3048 to 1.4: don't watch non-existent include directory (#3174)

fix(local-toolchains): don't watch non-existent include directory (#3048)

Apparently, Macs can mis-report their include directory.

Since includes are only needed if C extensions are built, skip watching
the directory
if it doesn't exist.

Work around for
#3043

---------

Co-authored-by: Richard Levasseur <[email protected]>
Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: Ignas Anikevicius <[email protected]>

Author: 4 people

CHANGELOG.md

@@ -48,6 +48,17 @@ END_UNRELEASED_TEMPLATE
 -->
 
 
+{#1-4-2}
+## [1.4.2] - 2025-08-13
+
+[1.4.2]: https://github.com/bazel-contrib/rules_python/releases/tag/1.4.2
+
+### Fixed
+* (toolchains) `local_runtime_repo` now checks if the include directory exists
+  before attempting to watch it, fixing issues on macOS with system Python
+  ([#3043](https://github.com/bazel-contrib/rules_python/issues/3043)).
+
+
 {#1-4-1}
 ## [1.4.1] - 2025-05-08
 

python/private/local_runtime_repo.bzl

@@ -85,7 +85,15 @@ def _local_runtime_repo_impl(rctx):
     logger.info(lambda: _format_get_info_result(info))
 
     # NOTE: Keep in sync with recursive glob in define_local_runtime_toolchain_impl
-    repo_utils.watch_tree(rctx, rctx.path(info["include"]))
+    include_path = rctx.path(info["include"])
+
+    # The reported include path may not exist, and watching a non-existant
+    # path is an error. Silently skip, since includes are only necessary
+    # if C extensions are built.
+    if include_path.exists and include_path.is_dir:
+        repo_utils.watch_tree(rctx, include_path)
+    else:
+        pass
 
     # The cc_library.includes values have to be non-absolute paths, otherwise
     # the toolchain will give an error. Work around this error by making them