Add static file infrastructure for generated clients

This commit adds the ability to include static Python files in generated
clients, which is essential for implementing shared utilities and modules
that don't need to be templated.

Changes:
- Add StaticFile model to represent static content
- Extend ConversionResult to include static_files list
- Create static_file_generator.py module (currently returns empty list)
- Update write_data() to write static files to output directory
- Add comprehensive tests for static file generation

This infrastructure will be used for Issue #100 enhanced error handling:
- errors.py: Exception hierarchy (APIError, ClientError, ServerError)
- response.py: DetailedResponse wrapper with fluent API
- utils.py: Helper functions (unwrap, expect, match, type guards)

All tests passing. Ready for static file content in follow-up PRs.

Related to #100

Author: Doug Borg

src/openapi_python_generator/generate_data.py

@@ -186,6 +186,10 @@ def write_data(
     # Write the api_config.py file.
     write_code(Path(output) / "api_config.py", data.api_config.content, formatter)
 
+    # Write static files (if any).
+    for static_file in data.static_files:
+        write_code(Path(output) / f"{static_file.file_name}.py", static_file.content, formatter)
+
     # Write the __init__.py file.
     write_code(
         Path(output) / "__init__.py",

src/openapi_python_generator/language_converters/python/generator.py

@@ -14,6 +14,9 @@
 from openapi_python_generator.language_converters.python.service_generator import (
     generate_services,
 )
+from openapi_python_generator.language_converters.python.static_file_generator import (
+    generate_static_files,
+)
 from openapi_python_generator.models import ConversionResult, LibraryConfig
 
 # Type alias for both OpenAPI versions
@@ -46,9 +49,11 @@ def generator(
         services = []
 
     api_config = generate_api_config(data, env_token_name, pydantic_version)
+    static_files = generate_static_files()
 
     return ConversionResult(
         models=models,
         services=services,
         api_config=api_config,
+        static_files=static_files,
     )

src/openapi_python_generator/language_converters/python/static_file_generator.py

@@ -0,0 +1,14 @@
+"""Generator for static files that are copied to the generated client."""
+from typing import List
+
+from ...models import StaticFile
+
+
+def generate_static_files() -> List[StaticFile]:
+    """
+    Generate static files that will be copied to the generated client.
+
+    Returns:
+        List of StaticFile objects containing file names and content.
+    """
+    return []

src/openapi_python_generator/models.py

@@ -94,7 +94,13 @@ class APIConfig(BaseModel):
     content: str
 
 
+class StaticFile(BaseModel):
+    file_name: str
+    content: str
+
+
 class ConversionResult(BaseModel):
     models: List[Model]
     services: List[Service]
     api_config: APIConfig
+    static_files: List[StaticFile] = []

tests/test_static_files.py

@@ -0,0 +1,72 @@
+"""Test static file generation and inclusion."""
+import tempfile
+from pathlib import Path
+
+from openapi_python_generator.common import Formatter
+from openapi_python_generator.generate_data import write_data
+from openapi_python_generator.models import ConversionResult, APIConfig, StaticFile
+
+
+def test_static_files_are_written():
+    """Test that static files are written to the output directory."""
+    # Create a minimal ConversionResult with static files
+    result = ConversionResult(
+        models=[],
+        services=[],
+        api_config=APIConfig(
+            file_name="api_config",
+            base_url="https://api.example.com",
+            content='class APIConfig:\n    pass\n',
+        ),
+        static_files=[
+            StaticFile(
+                file_name="errors",
+                content='"""Error types."""\nclass APIError(Exception):\n    pass\n',
+            ),
+            StaticFile(
+                file_name="response",
+                content='"""Response wrapper."""\nclass DetailedResponse:\n    pass\n',
+            ),
+        ],
+    )
+
+    # Write to temp directory
+    with tempfile.TemporaryDirectory() as tmpdir:
+        output_path = Path(tmpdir) / "generated"
+        write_data(result, output_path, Formatter.NONE)
+
+        # Verify static files were created
+        assert (output_path / "errors.py").exists()
+        assert (output_path / "response.py").exists()
+
+        # Verify content
+        errors_content = (output_path / "errors.py").read_text()
+        assert "class APIError" in errors_content
+
+        response_content = (output_path / "response.py").read_text()
+        assert "class DetailedResponse" in response_content
+
+
+def test_empty_static_files():
+    """Test that empty static files list doesn't cause issues."""
+    result = ConversionResult(
+        models=[],
+        services=[],
+        api_config=APIConfig(
+            file_name="api_config",
+            base_url="https://api.example.com",
+            content='class APIConfig:\n    pass\n',
+        ),
+        static_files=[],  # Empty list
+    )
+
+    # Write to temp directory
+    with tempfile.TemporaryDirectory() as tmpdir:
+        output_path = Path(tmpdir) / "generated"
+        write_data(result, output_path, Formatter.NONE)
+
+        # Verify basic structure still created
+        assert (output_path / "api_config.py").exists()
+        assert (output_path / "__init__.py").exists()
+        assert (output_path / "models").is_dir()
+        assert (output_path / "services").is_dir()