add changes to new _compat/v2 module

fastapi/_compat/v2.py

@@ -180,8 +180,13 @@ def get_schema_from_model_field(
     ],
     separate_input_output_schemas: bool = True,
 ) -> Dict[str, Any]:
+    computed_fields = field._type_adapter.core_schema.get("schema", {}).get(
+        "computed_fields", []
+    )
     override_mode: Union[Literal["validation"], None] = (
-        None if separate_input_output_schemas else "validation"
+        None
+        if (separate_input_output_schemas or len(computed_fields) > 0)
+        else "validation"
     )
     # This expects that GenerateJsonSchema was already used to generate the definitions
     json_schema = field_mapping[(field, override_mode or field.mode)]
@@ -203,9 +208,16 @@ def get_definitions(
     Dict[Tuple[ModelField, Literal["validation", "serialization"]], JsonSchemaValue],
     Dict[str, Dict[str, Any]],
 ]:
+    has_computed_fields: bool = any(
+        field._type_adapter.core_schema.get("schema", {}).get("computed_fields", [])
+        for field in fields
+    )
+
     schema_generator = GenerateJsonSchema(ref_template=REF_TEMPLATE)
     override_mode: Union[Literal["validation"], None] = (
-        None if separate_input_output_schemas else "validation"
+        None
+        if (separate_input_output_schemas or has_computed_fields)
+        else "validation"
     )
     flat_models = get_flat_models_from_fields(fields, known_models=set())
     flat_model_fields = [