Fix stdlib detection incorrectly flagging site-packages files

[Copilot]

Users receive "Skipping standard library file (stdlib excluded)" notifications for third-party packages in site-packages (e.g., pytest, numpy), which are not stdlib files.

Root Cause

_stdlib_paths incorrectly included:

• site.getsitepackages() / site.getusersitepackages() - third-party package directories
• purelib/platlib from sysconfig.get_paths() - also site-packages paths

Changes

bundled/tool/lsp_utils.py:

• _get_sys_config_paths(): Only include stdlib and platstdlib from sysconfig.get_paths()
• _stdlib_paths: Remove site.getsitepackages() and site.getusersitepackages()
• is_stdlib_file(): Add explicit exclusion for paths containing {os.sep}site-packages{os.sep} or {os.sep}dist-packages{os.sep} to handle edge cases

src/test/python_tests/test_stdlib_detection.py:

• New test suite validating stdlib vs site-packages detection
• Includes path segment matching validation (e.g., site-packages-backup ≠ site-packages)

Example

# Before: incorrectly detected as stdlib
is_stdlib_file("/usr/lib/python3.12/site-packages/pytest/__init__.py")  # True ❌

# After: correctly identified as third-party
is_stdlib_file("/usr/lib/python3.12/site-packages/pytest/__init__.py")  # False ✓
is_stdlib_file("/usr/lib/python3.12/os.py")  # True ✓

Original prompt

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This section details on the original issue you should resolve

<issue_title>Skipping standard library file notification</issue_title>
<issue_description><!-- Hello! Thank you for submitting a bug to our repo. Our users and their bug reports are essential to our development process.
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   of the bug report below! (see directions on how to set and access these logs in the Logs section below.)
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Diagnostic Data

• Python version (& distribution if applicable, e.g., Anaconda): 3.13
• Type of virtual environment used (e.g., conda, venv, virtualenv, etc.): venv
• Operating system (and version): Windows 11 Enterprise 10.0.26200
• Version of tool extension you are using: 2025.2.0

Behaviour

Expected Behavior

No notifications during normal use.

Actual Behavior

Repeated 'Skipping standard library file (stdlib excluded)' notifications with a path pointing to site-packages.

Reproduction Steps:

I don't think I've done anything special, I have a venv (created using python -m venv <path>) activated and write code. The latest notification that showed up today was for monkeypatch, so maybe writing a pytest test using monkeypatch. Importantly, I did not open any file in site-packages.

Logs:

Unfortunately the logs include sensitive client information. I have included a redacted version (mostly removing filenames/paths).

Click here for detailed logs

2025-12-02 12:04:43.949 [info] [Trace - 12:04:43 PM] Sending request 'textDocument/codeAction - (1451)'. 2025-12-02 12:04:43.949 [info] Params: { "textDocument": { "uri": "--redacted--" }, "range": { "start": { "line": 32, "character": 0 }, "end": { "line": 40, "character": 0 } }, "context": { "diagnostics": [], "triggerKind": 2 } }

2025-12-02 12:04:43.952 [info] [Trace - 12:04:43 PM] Received response 'textDocument/codeAction - (1451)' in 3ms.
2025-12-02 12:04:43.952 [info] Result: []

2025-12-02 12:04:45.241 [info] [Trace - 12:04:45 PM] Sending notification 'textDocument/didChange'.
2025-12-02 12:04:45.241 [info] Params: {
"textDocument": {
"uri": "--redacted--",
"version": 3281
},
"contentChanges": [
{
"range": {
"start": {
"line": 32,
"character": 0
},
"end": {
"line": 40,
"character": 0
}
},
"rangeLength": 199,
"text": ""
}
]
}

2025-12-02 12:04:47.077 [info] [Trace - 12:04:47 PM] Sending notification 'textDocument/didOpen'.
2025-12-02 12:04:47.077 [info] Params: {
"textDocument": {
"uri": "file:///c%3A/--venv path--/Lib/site-packages/pytest_bdd/steps.py",
"languageId": "python",
"version": 1,
"text": """"Step decorators.\n\nExample:\n\n@given("I have an article", target_fixture="article")\ndef _(author):\n return create_test_article(author=author)\n\n\n@when("I go to the article page")\ndef _(browser, article):\n browser.visit(urljoin(browser.url, "/articles/{0}/".format(article.id)))\n\n\n@then("I should not see the error message")\ndef _(browser):\n with pytest.raises(ElementDoesNotExist):\n browser.find_by_css(".message.error").first\n\n\nMultiple names for the steps:\n\n@given("I have an article")\n@given("there is an article")\ndef _(author):\n return create_test_article(author=author)\n\n\nReusing existing fixtures for a different step name:\n\n\n@given("I have a beautiful article")\ndef _(article):\n pass\n\n"""\n\nfrom future import annotations\n\nimport enum\nfrom collections.abc import Iterable\nfrom dataclasses import dataclass, field\nfrom itertools import count\nfrom typing import Any, Callable, Literal, TypeVar\n\nimport pytest\nfrom typing_extensions import ParamS...

• Fixes Skipping standard library file notification #357

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[rchiodo]

Approved via Review Center.