Merge 1752749e70 into 460f8d2cc8

fastapi/dependencies/utils.py

@@ -243,11 +243,42 @@ def get_typed_signature(call: Callable[..., Any]) -> inspect.Signature:
 
 
 def get_typed_annotation(annotation: Any, globalns: dict[str, Any]) -> Any:
+    # Resolve bare string / ForwardRef annotations (e.g. produced by
+    # `from __future__ import annotations` when the annotation itself is a
+    # plain type name).
     if isinstance(annotation, str):
         annotation = ForwardRef(annotation)
         annotation = evaluate_forwardref(annotation, globalns, globalns)
         if annotation is type(None):
             return None
+
+    # When `from __future__ import annotations` is active, the *base* type
+    # inside `Annotated[SomeType, ...]` may still be a string or ForwardRef
+    # even after the outer annotation has been evaluated.  Handle that by
+    # resolving the base type and reconstructing the Annotated alias.
+    if get_origin(annotation) is Annotated:
+        args = get_args(annotation)
+        # args[0] is the base type; args[1:] are the metadata (Depends, etc.)
+        base_type = args[0]
+        metadata = args[1:]
+
+        # Resolve the base type if it is still a string or ForwardRef
+        if isinstance(base_type, str):
+            base_type = ForwardRef(base_type)
+        if isinstance(base_type, ForwardRef):
+            base_type = evaluate_forwardref(base_type, globalns, globalns)
+
+        # Recursively resolve in case of nested Annotated / ForwardRef
+        base_type = get_typed_annotation(base_type, globalns)
+
+        # Keep NoneType handling consistent with the bare-string path above
+        if base_type is type(None):
+            base_type = None
+
+        # Reconstruct Annotated correctly via __class_getitem__ so that
+        # Annotated[T, meta1, meta2] is produced, not Annotated[(T, meta1, meta2)].
+        annotation = Annotated.__class_getitem__((base_type, *metadata))
+
     return annotation
 
 

tests/test_annotated_forwardref.py

@@ -0,0 +1,56 @@
+# IMPORTANT: This future import MUST be at the top of the module.
+# It is what causes annotations to be stored as strings (ForwardRef),
+# which is exactly the bug scenario described in issue #13056.
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Annotated
+
+from fastapi import Depends, FastAPI
+from fastapi.testclient import TestClient
+
+# ── App setup ─────────────────────────────────────────────────────────────────
+
+
+app = FastAPI()
+
+
+@dataclass
+class Potato:
+    color: str
+    size: int
+
+
+def get_potato() -> Potato:
+    return Potato(color="red", size=10)
+
+
+# The annotation "Potato" is a string here because of `from __future__ import
+# annotations`.  Before the fix, FastAPI would fail to resolve it when it is
+# wrapped inside Annotated[...].
+@app.get("/")
+def read_root(potato: Annotated[Potato, Depends(get_potato)]) -> dict:
+    return {"color": potato.color, "size": potato.size}
+
+
+client = TestClient(app)
+
+
+# ── Tests ──────────────────────────────────────────────────────────────────────
+
+
+def test_annotated_forwardref_response() -> None:
+    """Endpoint using Annotated[ForwardRef, Depends(...)] must return 200."""
+    response = client.get("/")
+    assert response.status_code == 200
+    assert response.json() == {"color": "red", "size": 10}
+
+
+def test_annotated_forwardref_openapi_schema() -> None:
+    """OpenAPI schema must be generated without errors and must not leak ForwardRef."""
+    response = client.get("/openapi.json")
+    assert response.status_code == 200
+    schema_text = response.text
+    assert "ForwardRef" not in schema_text, (
+        "Unresolved ForwardRef leaked into the OpenAPI schema"
+    )

tests/test_dependencies_utils.py

@@ -1,8 +1,73 @@
+# NOTE: Do NOT add `from __future__ import annotations` here.
+# That future import would turn the string subscripts in Annotated[...] bodies
+# into deferred references and break isinstance() checks in this file.
+
+from typing import Annotated, ForwardRef, get_args, get_origin
+
+from fastapi import params
 from fastapi.dependencies.utils import get_typed_annotation
 
+# ---------------------------------------------------------------------------
+# Existing coverage test
+# ---------------------------------------------------------------------------
+
 
-def test_get_typed_annotation():
+def test_get_typed_annotation_none_string() -> None:
-    # For coverage
+    # A bare "None" string should resolve to Python's NoneType (returned as None)
-    annotation = "None"
+    typed_annotation = get_typed_annotation("None", globals())
-    typed_annotation = get_typed_annotation(annotation, globals())
     assert typed_annotation is None
+
+
+# ---------------------------------------------------------------------------
+# Issue #13056 – ForwardRef inside Annotated
+# ---------------------------------------------------------------------------
+
+
+class _Potato:
+    """Stand-in model used by the tests below."""
+
+
+def _get_potato() -> "_Potato":
+    return _Potato()
+
+
+def test_annotated_with_string_base_type() -> None:
+    """Annotated["_Potato", Depends(...)] must resolve the base type."""
+    dep = params.Depends(_get_potato)
+    annotation = Annotated["_Potato", dep]
+    resolved = get_typed_annotation(annotation, globals())
+
+    assert get_origin(resolved) is Annotated
+    args = get_args(resolved)
+    assert args[0] is _Potato, f"Expected _Potato, got {args[0]}"
+    assert isinstance(args[1], params.Depends)
+
+
+def test_annotated_with_forwardref_base_type() -> None:
+    """Annotated[ForwardRef("_Potato"), Depends(...)] must also resolve."""
+    dep = params.Depends(_get_potato)
+    annotation = Annotated[ForwardRef("_Potato"), dep]
+    resolved = get_typed_annotation(annotation, globals())
+
+    assert get_origin(resolved) is Annotated
+    args = get_args(resolved)
+    assert args[0] is _Potato, f"Expected _Potato, got {args[0]}"
+    assert isinstance(args[1], params.Depends)
+
+
+def test_annotated_with_already_resolved_type() -> None:
+    """Annotated[_Potato, Depends(...)] (already resolved) must pass through unchanged."""
+    dep = params.Depends(_get_potato)
+    annotation = Annotated[_Potato, dep]
+    resolved = get_typed_annotation(annotation, globals())
+
+    assert get_origin(resolved) is Annotated
+    args = get_args(resolved)
+    assert args[0] is _Potato
+    assert isinstance(args[1], params.Depends)
+
+
+def test_bare_string_annotation() -> None:
+    """A bare string annotation (non-Annotated) must still resolve correctly."""
+    resolved = get_typed_annotation("_Potato", globals())
+    assert resolved is _Potato