gh-135801: Fix inaccurate module info for SyntaxWarnings during AST parsing

[heliang666s]

This commit addresses the inaccurate module information provided for SyntaxWarnings during AST parsing, specifically reported in issue #135801.

Previously, _PyErr_EmitSyntaxWarning (used by the compiler) relied on _PyErr_WarnExplicitObjectWithContext to infer the module name from the call stack. During compilation, this often resulted in misleading module names like sys or importlib._bootstrap, making it difficult to filter warnings effectively (e.g., using -W error::SyntaxWarning:test).

To resolve this, a new internal function _PyErr_EmitSyntaxWarningFromCompiler was introduced in Python/errors.c. This function explicitly calls PyErr_WarnExplicitObject with a NULL module argument, forcing the warning system to derive the module name from the filename provided by the compiler.

The normalize_module function in Python/_warnings.c was also refined. Instead of simple string manipulation or problematic pure C path parsing, it now leverages Python's os.path module (via Python C API calls like basename, splitext, and dirname). This ensures robust and accurate extraction of module names from arbitrary file paths, including correct handling of __init__.py files, thereby providing correct module information for compiler-generated SyntaxWarning messages.

This approach ensures cross-platform compatibility and reliability by utilizing Python's battle-tested path handling capabilities, directly addressing the core issue reported.

• Issue: Improve/fix filtering SyntaxWarnings by module #135801

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[heliang666s]

@iritkatriel please review again，thanks～

[cdce8p]

Any update here?

CC @hugovk I believe this would address some / most of the concerns raised on the forum post for PEP 765. It might make sense for 3.14.
https://discuss.python.org/t/pep-765-disallow-return-break-continue-that-exit-a-finally-block/71348/146

[gpshead]

FWIW this seems like something that could make sense as a later bugfix in a patch release.

Deciding that mostly requires understanding if there are meaningful load bearing behavior changes that code might be relying upon in this PRs warnings and errors changes.

[serhiy-storchaka]

The normalize_module() change does not match the Python implementation and the documented behavior. Is it necessary to include it in this PR?