test: Add tests documenting Pydantic Field behavior #558
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This commit adds test cases for four reported issues: 1. Issue facebook#547: Dict narrowing after None checks - Already fixed in current version - Tests confirm proper type narrowing for Optional[Dict] after is not None checks - Tests cover attribute chains, early returns, and nested narrowing 2. Issue facebook#548: Pydantic Field overload resolution - Tests document expected behavior with positional arguments - Issue stems from Pydantic's use of sentinel values in type stubs - Workaround: use keyword arguments (default=value) 3. Issue facebook#549: False positives on union types with Any - Added type_contains_any() helper to check for Any in unions - When Any is present in a union, allow any attribute access without errors - Partial fix: works for explicit unions, Dict[str, Any] needs separate handling 4. Issue facebook#550: Init helper methods - Tests document the limitation that helper methods aren't recognized - Full fix requires flow analysis to track methods called from __init__ These tests improve code coverage and document both working features and known limitations, providing a foundation for future improvements.
These tests document the expected behavior for Pydantic Field overload resolution and confirm that using keyword arguments works as a workaround. The issue stems from how Pydantic uses sentinel values in type stubs, which causes overload matching to fail with positional arguments. Related to facebook#548
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Related to #548 |
yangdanny97
requested changes
Jun 24, 2025
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Summary
This PR adds tests documenting the expected behavior for Pydantic Field overload resolution.
Issue #548: Pydantic Field Overload Resolution Failure
The issue reports that Pyrefly fails to match Pydantic Field overloads when using positional default arguments.
Root Cause
The issue stems from how Pydantic uses sentinel values (
_Unset/PydanticUndefined) in its type stubs. These sentinel values make parameters appear as having defaults when they should be treated as required from a caller's perspective.Tests Added
The test file
issue_548_pydantic_field.rsincludes:Workaround
Users can work around this issue by using keyword arguments:
Related to #548 - This PR documents the current behavior and workaround rather than fixing the underlying issue.