Fix FutureWarning from datamodel-code-generator by setting explicit formatters

Pass BLACK and ISORT formatters explicitly to JsonSchemaParser to avoid
the FutureWarning about default formatters changing in a future version.

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

Author: krasserm

mcpygen/apigen.py

@@ -8,13 +8,15 @@
 
 import aiofiles
 import aiofiles.os
-from datamodel_code_generator import DataModelType, PythonVersion
+from datamodel_code_generator import DataModelType, Formatter, PythonVersion
 from datamodel_code_generator.model import get_data_model_types
 from datamodel_code_generator.model.base import ALL_MODEL
 from datamodel_code_generator.parser.jsonschema import JsonSchemaParser
 
 from mcpygen.client import MCPClient
 
+_DEFAULT_FORMATTERS: list[Formatter] = [Formatter.BLACK, Formatter.ISORT]
+
 
 def generate_init_definition(server_name: str, server_params: dict[str, Any]) -> str:
     return f"""\
@@ -76,6 +78,7 @@ def generate_output_model_code(schema: dict[str, Any]) -> str:
 
 
 def _generate_model_code(schema: dict[str, Any], class_name: str) -> str:
+    """Generate a Pydantic model from JSON schema."""
     data_model_types = get_data_model_types(
         data_model_type=DataModelType.PydanticV2BaseModel,
         target_python_version=PythonVersion.PY_311,
@@ -95,6 +98,7 @@ def _generate_model_code(schema: dict[str, Any], class_name: str) -> str:
         use_field_description=True,
         use_double_quotes=True,
         extra_template_data=extra_template_data,
+        formatters=_DEFAULT_FORMATTERS,
     )
     return parser.parse()
 

tests/unit/test_apigen.py

@@ -1,6 +1,8 @@
 import ast
+import warnings
 
 from mcpygen.apigen import (
+    _generate_model_code,
     generate_function_definition,
     generate_init_definition,
     sanitize_name,
@@ -198,3 +200,24 @@ def test_dots_replaced(self):
 
     def test_already_valid(self):
         assert sanitize_name("my_tool_123") == "my_tool_123"
+
+
+class TestGenerateModelCode:
+    def test_explicit_formatters_avoid_futurewarning(self) -> None:
+        schema = {
+            "type": "object",
+            "properties": {
+                "q": {"type": "string"},
+            },
+            "required": ["q"],
+        }
+
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            code = _generate_model_code(schema, "Params")
+
+        assert "class Params" in code
+        assert not any(
+            warning.category is FutureWarning and "default formatters" in str(warning.message).lower()
+            for warning in caught
+        )