Add static file infrastructure for generated clients

[dougborg]

Summary

This PR adds the foundational infrastructure for including static Python files in generated clients. This capability is essential for the enhanced error handling feature (#100) which requires shared utilities and exception classes.

Changes

Core Infrastructure

• StaticFile Model (models.py): New model to represent static file content
• ConversionResult Extension (models.py): Added static_files: List[StaticFile] field
• Static File Generator (static_file_generator.py): New module (currently returns empty list, ready for content)
• Write Integration (generate_data.py): Writes static files to output directory
• Generator Integration (generator.py): Calls static file generator and includes in result

Tests

• Comprehensive Testing (test_static_files.py):
  • Verifies static files are written correctly
  • Tests empty static files list (backwards compat)
  • All existing tests still pass

How It Works

# In static_file_generator.py (ready for content)
def generate_static_files() -> List[StaticFile]:
    return [
        StaticFile(
            file_name="errors",
            content="# Exception classes here"
        ),
        # More static files...
    ]

Static files are:

1. Generated by generate_static_files()
2. Included in ConversionResult
3. Written to output root (same level as api_config.py)
4. Formatted with Black/isort
5. Available for import in generated services

Use Case: Issue #100

This infrastructure enables the enhanced error handling feature by allowing us to ship:

• errors.py: Exception hierarchy (APIError, ClientError, ServerError)
• response.py: DetailedResponse wrapper with fluent API
• utils.py: Helper functions (unwrap, expect, match, type guards)

These modules will be shared across all generated services without requiring template generation.

Testing

✅ All existing tests pass (257 tests)
✅ New tests verify static file generation
✅ Backwards compatible (empty list by default)
✅ 95%+ code coverage maintained

Status

• Infrastructure implemented
• Tests passing
• Static file content (follow-up PRs per Enhance generated HTTPException: rich context, parsed error models, configurable handling #100 design)

Related

• Part of Enhance generated HTTPException: rich context, parsed error models, configurable handling #100 (Enhanced Error Handling)
• Blocked by: Nothing - ready to merge
• Blocks: Implementation phases of Enhance generated HTTPException: rich context, parsed error models, configurable handling #100

[Copilot]

Pull Request Overview

This PR establishes the foundational infrastructure for including static Python files (like shared utilities and exception classes) in generated API clients, preparing for the enhanced error handling feature described in issue #100.

• Adds StaticFile model and integrates static file generation into the conversion pipeline
• Implements file writing logic that places static files at the output root alongside api_config.py
• Provides comprehensive test coverage for static file generation and backwards compatibility

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/openapi_python_generator/models.py	Adds StaticFile model and extends ConversionResult with static_files field
src/openapi_python_generator/language_converters/python/static_file_generator.py	Creates new module with generate_static_files() function (currently returns empty list)
src/openapi_python_generator/language_converters/python/generator.py	Integrates static file generation into the conversion pipeline
src/openapi_python_generator/generate_data.py	Implements writing logic for static files to output directory
tests/test_static_files.py	Adds comprehensive tests for static file generation and backwards compatibility

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