feat: add JSON serialization tests for OCROptions in multiprocessing

Co-authored-by: aider (openrouter/anthropic/claude-sonnet-4) <aider@aider.chat>

tests/test_json_serialization.py

@@ -0,0 +1,133 @@
+"""Test JSON serialization of OCROptions for multiprocessing compatibility."""
+
+import multiprocessing
+from pathlib import Path
+from io import BytesIO
+
+import pytest
+
+from ocrmypdf._options import OCROptions
+
+
+def worker_function(options_json: str) -> str:
+    """Worker function that deserializes OCROptions from JSON and returns a result."""
+    # Reconstruct OCROptions from JSON in worker process
+    options = OCROptions.model_validate_json_safe(options_json)
+    
+    # Verify we can access various option types
+    result = {
+        'input_file': str(options.input_file),
+        'output_file': str(options.output_file),
+        'languages': options.languages,
+        'optimize': options.optimize,
+        'tesseract_timeout': options.tesseract_timeout,
+        'fast_web_view': options.fast_web_view,
+        'extra_attrs_count': len(options.extra_attrs),
+    }
+    
+    # Return as JSON string
+    import json
+    return json.dumps(result)
+
+
+def test_json_serialization_multiprocessing():
+    """Test that OCROptions can be JSON serialized and used in multiprocessing."""
+    # Create OCROptions with various field types
+    options = OCROptions(
+        input_file=Path('/test/input.pdf'),
+        output_file=Path('/test/output.pdf'),
+        languages=['eng', 'deu'],
+        optimize=2,
+        tesseract_timeout=120.0,
+        fast_web_view=2.5,
+        deskew=True,
+        clean=False,
+    )
+    
+    # Add some extra attributes
+    options.extra_attrs['custom_field'] = 'test_value'
+    options.extra_attrs['numeric_field'] = 42
+    
+    # Serialize to JSON
+    options_json = options.model_dump_json_safe()
+    
+    # Test that we can deserialize in the main process
+    reconstructed = OCROptions.model_validate_json_safe(options_json)
+    assert reconstructed.input_file == options.input_file
+    assert reconstructed.output_file == options.output_file
+    assert reconstructed.languages == options.languages
+    assert reconstructed.optimize == options.optimize
+    assert reconstructed.tesseract_timeout == options.tesseract_timeout
+    assert reconstructed.fast_web_view == options.fast_web_view
+    assert reconstructed.deskew == options.deskew
+    assert reconstructed.clean == options.clean
+    assert reconstructed.extra_attrs == options.extra_attrs
+    
+    # Test multiprocessing with JSON serialization
+    with multiprocessing.Pool(processes=2) as pool:
+        # Send the JSON string to worker processes
+        results = pool.map(worker_function, [options_json, options_json])
+    
+    # Verify results from worker processes
+    import json
+    for result_json in results:
+        result = json.loads(result_json)
+        assert result['input_file'] == '/test/input.pdf'
+        assert result['output_file'] == '/test/output.pdf'
+        assert result['languages'] == ['eng', 'deu']
+        assert result['optimize'] == 2
+        assert result['tesseract_timeout'] == 120.0
+        assert result['fast_web_view'] == 2.5
+        assert result['extra_attrs_count'] == 2
+
+
+def test_json_serialization_with_streams():
+    """Test JSON serialization with stream objects."""
+    input_stream = BytesIO(b'fake pdf data')
+    output_stream = BytesIO()
+    
+    options = OCROptions(
+        input_file=input_stream,
+        output_file=output_stream,
+        languages=['eng'],
+        optimize=1,
+    )
+    
+    # Serialize to JSON (streams should be converted to placeholders)
+    options_json = options.model_dump_json_safe()
+    
+    # Deserialize (streams will be placeholder strings)
+    reconstructed = OCROptions.model_validate_json_safe(options_json)
+    
+    # Streams should be converted to placeholder strings
+    assert reconstructed.input_file == 'stream'
+    assert reconstructed.output_file == 'stream'
+    assert reconstructed.languages == ['eng']
+    assert reconstructed.optimize == 1
+
+
+def test_json_serialization_with_none_values():
+    """Test JSON serialization handles None values correctly."""
+    options = OCROptions(
+        input_file=Path('/test/input.pdf'),
+        output_file=Path('/test/output.pdf'),
+        languages=['eng'],
+        # Many fields will be None by default
+    )
+    
+    # Serialize to JSON
+    options_json = options.model_dump_json_safe()
+    
+    # Deserialize
+    reconstructed = OCROptions.model_validate_json_safe(options_json)
+    
+    # Verify None values are preserved
+    assert reconstructed.tesseract_timeout is None
+    assert reconstructed.fast_web_view is None
+    assert reconstructed.color_conversion_strategy is None
+    assert reconstructed.pdfa_image_compression is None
+    
+    # Verify non-None values are preserved
+    assert reconstructed.input_file == options.input_file
+    assert reconstructed.output_file == options.output_file
+    assert reconstructed.languages == options.languages