Fix an intriduced bug in parsing json field with discriminated union (#…

…312)

pydantic_settings/sources.py

@@ -1597,8 +1597,8 @@ def _annotation_is_complex(annotation: type[Any] | None, metadata: list[Any]) ->
     # Check if annotation is of the form Annotated[type, metadata].
     if isinstance(annotation, _AnnotatedAlias):
         # Return result of recursive call on inner type.
-        inner, meta = get_args(annotation)
-        return _annotation_is_complex(inner, [meta])
+        inner, *meta = get_args(annotation)
+        return _annotation_is_complex(inner, meta)
     origin = get_origin(annotation)
     return (
         _annotation_is_complex_inner(annotation)

tests/test_settings.py

@@ -1767,6 +1767,26 @@ class Settings(BaseSettings):
     assert s.a_or_b.y == 'foo'
 
 
+def test_json_field_with_discriminated_union(env):
+    class A(BaseModel):
+        x: Literal['a'] = 'a'
+
+    class B(BaseModel):
+        x: Literal['b'] = 'b'
+
+    A_OR_B = Annotated[Union[A, B], Field(discriminator='x')]
+
+    class Settings(BaseSettings):
+        a_or_b: Optional[Json[A_OR_B]] = None
+
+    # Set up environment so that the discriminator is 'a'.
+    env.set('a_or_b', '{"x": "a"}')
+
+    s = Settings()
+
+    assert s.a_or_b.x == 'a'
+
+
 def test_nested_model_case_insensitive(env):
     class SubSubSub(BaseModel):
         VaL3: str