When using rom __future__ import annotations, annotations are stored as
strings. If Annotated[SomeClass, Depends()] references a class defined
after the route decorator, the forward reference could not be resolved at
decoration time.
FastAPI's evaluate_forwardref() does not raise on unresolvable references
- it returns the raw ForwardRef object. The existing code only handled the
string-to-ForwardRef conversion but did not check whether resolution
actually succeeded, allowing an unresolvable ForwardRef to leak into the
type annotation. This caused Pydantic to fail with
'class-not-fully-defined' errors and the Depends metadata to be lost.
The fix adds a fallback: when evaluate_forwardref() returns a ForwardRef
(rather than the resolved type) and the annotation string is Annotated-
shaped, a lenient resolution evaluates the annotation with a namespace
that maps undefined names to Any. This preserves the Annotated structure
so FastAPI can extract the Depends metadata.
Codebuff Contributor
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