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# Transform Types
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Types for Jest's code transformation system enabling custom transformers and build tool integration. These types are designed to avoid huge dependency trees while providing the necessary interfaces for code transformation.
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## Capabilities
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### Transform Result Interface
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Core interface for the result of code transformation operations.
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```typescript { .api }
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/**
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 * Result of code transformation
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 * Designed to avoid huge dependency trees for transformation processing
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 */
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interface TransformResult {
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  /** Transformed code output */
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  code: string;
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  /** Original source code before transformation */
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  originalCode: string;
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  /** Path to source map file, or null if no source map */
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  sourceMapPath: string | null;
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}
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```
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**Usage Examples:**
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```typescript
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import type { TransformTypes } from "@jest/types";
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// Custom transformer function signature
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type CustomTransformer = (
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  source: string,
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  filename: string,
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  options?: any
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) => TransformTypes.TransformResult;
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// Example transformer implementation
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const myTransformer: CustomTransformer = (source, filename, options) => {
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  // Perform transformation logic
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  const transformedCode = transformSource(source, options);
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  return {
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    code: transformedCode,
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    originalCode: source,
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    sourceMapPath: `${filename}.map`,
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  };
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};
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// Process transform result
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const processTransformResult = (result: TransformTypes.TransformResult) => {
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  console.log('Transformed code length:', result.code.length);
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  console.log('Original code length:', result.originalCode.length);
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  if (result.sourceMapPath) {
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    console.log('Source map available at:', result.sourceMapPath);
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  }
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};
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// Check if transformation changed the code
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const isCodeTransformed = (result: TransformTypes.TransformResult): boolean => {
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  return result.code !== result.originalCode;
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};
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```