Python: Fail early on syntax errors - #22723
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Previously, we would only signal a syntax error when we created a SyntaxErrorNode from the tsg-python output. However, this meant that we might accidentally try to construct nodes based on bogus input (since if the file has a syntax error, then all bets are off). Instead, we now propagate the syntax error as soon as we encounter it (immediately after reading the output of tsg-python).
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Copilot review overview
🟢 Approval recommended
The implementation preserves existing error details while preventing AST construction from invalid parser output.
Review effort: Balanced
Findings: None
What changed in this PR
Moves tree-sitter syntax-error detection ahead of AST construction.
Changes:
- Raises
SyntaxErrorwhile decoding TSG output. - Adds a regression test validating error location data.
| File | Description |
|---|---|
python/extractor/semmle/python/parser/tsg_parser.py |
Detects syntax errors before constructing nodes. |
python/extractor/tests/test_tsg_parser.py |
Tests early failure and location propagation. |
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andersfugmann
approved these changes
Oct 2, 2026
andersfugmann
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andersfugmann
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Approved.
Consider if the class SyntaxErrorNode could be deleted, now that it's never constructed.
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Previously, we would only signal a syntax error when we created a SyntaxErrorNode from the tsg-python output. However, this meant that we might accidentally try to construct nodes based on bogus input (since if the file has a syntax error, then all bets are off).
Instead, we now propagate the syntax error as soon as we encounter it (immediately after reading the output of tsg-python).