Fix: fastapi_utils/cbv.py performed `if PYDANTIC_VERSION[0] == "2": from...

fastapi_utils/cbv.py

@@ -1,4 +1,5 @@
 import inspect
+import typing
 from typing import (
     Any,
     Callable,
@@ -18,7 +19,15 @@
 
 PYDANTIC_VERSION = pydantic.VERSION
 if PYDANTIC_VERSION[0] == "2":
-    from typing_inspect import is_classvar
+    # Implemented with the stdlib `typing` module rather than the optional
+    # `typing-inspect` dependency, so that simply importing `fastapi_utils`
+    # doesn't require an extra to be installed. This covers both the bare
+    # `ClassVar` and the subscripted `ClassVar[...]` forms, matching the
+    # behavior of `typing_inspect.is_classvar` for the annotations `cbv`
+    # encounters here.
+    def is_classvar(hint: Any) -> bool:
+        return hint is typing.ClassVar or typing.get_origin(hint) is typing.ClassVar
+
 else:
     from pydantic.typing import is_classvar  # type: ignore[no-redef]
 

tests/test_cbv.py

@@ -1,14 +1,36 @@
 from __future__ import annotations
 
+import importlib
+import sys
 from typing import Any, ClassVar, Optional
 
 import pytest
 from fastapi import APIRouter, Depends, Request
 from starlette.testclient import TestClient
 
+import fastapi_utils.cbv
 from fastapi_utils.cbv import cbv
 
 
+def test_cbv_importable_without_typing_inspect(monkeypatch: pytest.MonkeyPatch) -> None:
+    """`typing-inspect` is an optional dependency (only pulled in by the `all` extra), so
+    importing `fastapi_utils.cbv` must not require it to be installed. See #318.
+
+    Setting `sys.modules["typing_inspect"] = None` makes the import machinery raise
+    `ImportError` for any `import typing_inspect` / `from typing_inspect import ...`
+    statement, simulating an environment where the package isn't installed.
+    """
+    monkeypatch.setitem(sys.modules, "typing_inspect", None)
+
+    try:
+        reloaded = importlib.reload(fastapi_utils.cbv)
+        assert reloaded.cbv is not None
+    finally:
+        # Restore the real module state for any tests that run afterwards.
+        monkeypatch.undo()
+        importlib.reload(fastapi_utils.cbv)
+
+
 class TestCBV:
     @pytest.fixture(autouse=True)
     def router(self) -> APIRouter: