✅ Remove unreachable guard in get_sse_data_type; add subclass coverage test

Pydantic BaseModel subclasses always have __pydantic_generic_metadata__, so
the `if not meta` early-return was dead code. Collapse it into a ternary and
add a test for a plain (non-parameterized) ServerSentEvent subclass to reach
the `not args` branch, bringing fastapi/sse.py to 100% coverage.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: benmosher

fastapi/sse.py

@@ -264,9 +264,7 @@ def get_sse_data_type(annotation: Any) -> Any | None:
     if annotation is ServerSentEvent:
         return None
     meta = getattr(annotation, "__pydantic_generic_metadata__", None)
-    if not meta:
-        return None
-    args = meta.get("args", ())
+    args = meta.get("args", ()) if meta else ()
     if not args or isinstance(args[0], TypeVar):
         return None
     return args[0]

tests/test_sse.py

@@ -340,6 +340,15 @@ def test_get_sse_data_type_non_sse():
     assert get_sse_data_type(None) is None
 
 
+def test_get_sse_data_type_subclass_no_type_param():
+    """get_sse_data_type returns None for a plain ServerSentEvent subclass."""
+
+    class MyEvent(ServerSentEvent):
+        pass
+
+    assert get_sse_data_type(MyEvent) is None
+
+
 def test_generic_sse_construction_validates_data():
     """ServerSentEvent[Item] requires data to be an Item."""
     item = Item(name="Foo", description=None)