Allow the use of local-only stubtest allowlists (#11173)

This makes it nicer to work on a local system with known
divergences from the CI environment

.gitignore

@@ -71,3 +71,6 @@ analyze.py
 
 # pyenv local python version
 .python-version
+
+# deliberately local test configuration files
+tests/stubtest_allowlists/*.local

tests/README.md

@@ -133,6 +133,12 @@ test it automatically (or
 [running the test via Github Actions](https://docs.github.com/en/actions/managing-workflow-runs/manually-running-a-workflow#running-a-workflow)
 on your typeshed fork).
 
+As a convenience, stubtest\_stdlib.py will look for local-only allowlist files
+and use those if they are present. Only version-specific local allowlists are supported.
+An example local allowlist file is
+`tests/stubtest_allowlists/py312.txt.local`. Use caution when taking advantage of this feature;
+the CI run of stubtest remains canonical.
+
 If you need a specific version of Python to repro a CI failure,
 [pyenv](https://github.com/pyenv/pyenv) can also help.
 

tests/check_new_syntax.py

@@ -66,4 +66,5 @@ def main() -> None:
 
 
 if __name__ == "__main__":
+    assert sys.version_info >= (3, 9), "Python 3.9+ is required to run this test"
     main()

tests/stubtest_stdlib.py

@@ -18,6 +18,7 @@ def run_stubtest(typeshed_dir: Path) -> int:
     version_allowlist = f"py{sys.version_info.major}{sys.version_info.minor}.txt"
     platform_allowlist = f"{sys.platform}.txt"
     combined_allowlist = f"{sys.platform}-py{sys.version_info.major}{sys.version_info.minor}.txt"
+    local_version_allowlist = version_allowlist + ".local"
 
     # Note when stubtest imports distutils, it will likely actually import setuptools._distutils
     # This is fine because we don't care about distutils and allowlist all errors from it
@@ -39,6 +40,8 @@ def run_stubtest(typeshed_dir: Path) -> int:
         cmd += ["--allowlist", str(allowlist_dir / platform_allowlist)]
     if (allowlist_dir / combined_allowlist).exists():
         cmd += ["--allowlist", str(allowlist_dir / combined_allowlist)]
+    if (allowlist_dir / local_version_allowlist).exists():
+        cmd += ["--allowlist", str(allowlist_dir / local_version_allowlist)]
     if sys.version_info < (3, 10):
         # As discussed in https://github.com/python/typeshed/issues/3693, we only aim for
         # positional-only arg accuracy for python 3.10 and above.