Allow basic types used as serialization method to be json schema inst…

…ance type

mashumaro/jsonschema/schema.py

@@ -282,6 +282,9 @@ class Config(config_cls):  # type: ignore
 register = Registry.register
 
 
+BASIC_TYPES = {str, int, float, bool}
+
+
 @register
 def on_type_with_overridden_serialization(
     instance: Instance, ctx: Context
@@ -301,6 +304,8 @@ def override_with_any(reason: Any) -> None:
     overridden_method = instance.get_overridden_serialization_method()
     if overridden_method is pass_through:
         return None
+    elif overridden_method in BASIC_TYPES:
+        instance.update_type(overridden_method)  # type: ignore
     elif callable(overridden_method):
         try:
             new_type = get_function_return_annotation(overridden_method)

tests/test_jsonschema/test_jsonschema_generation.py

@@ -1019,6 +1019,36 @@ class Config(BaseConfig):
     )
 
 
+@pytest.mark.parametrize(
+    ("basic_type", "schema_type"),
+    (
+        (str, JSONSchemaInstanceType.STRING),
+        (int, JSONSchemaInstanceType.INTEGER),
+        (float, JSONSchemaInstanceType.NUMBER),
+        (bool, JSONSchemaInstanceType.BOOLEAN),
+    ),
+)
+def test_basic_type_as_overridden_serialization_method(
+    basic_type, schema_type
+):
+    @dataclass
+    class DataClass:
+        x: ThirdPartyType
+        y: List[ThirdPartyType]
+
+        class Config(BaseConfig):
+            serialization_strategy = {
+                ThirdPartyType: {"serialize": basic_type}
+            }
+
+    assert build_json_schema(DataClass).properties["x"] == JSONSchema(
+        type=schema_type
+    )
+    assert build_json_schema(DataClass).properties["y"] == JSONArraySchema(
+        items=JSONSchema(type=schema_type)
+    )
+
+
 def test_dataclass_overridden_serialization_method():
     def serialize_as_str(value: Any) -> str:
         return str(value)  # pragma no cover