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tessl/npm-parcel--transformer-babel

A Parcel transformer plugin that transforms JavaScript code using Babel with automatic configuration discovery and intelligent defaults for modern JavaScript, TypeScript, JSX, and Flow.

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Overview
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Files

error-handling.mddocs/

Error Handling

Enhanced error reporting and diagnostics for Babel compilation errors with source context and improved developer experience.

Capabilities

Babel Error Enhancement

Enhances Babel compilation errors with additional context and source information for better debugging experience.

/**
 * Enhances Babel errors with source context and file information
 * Improves error messages by removing redundant path information and adding source code
 * @param error - The original Babel error
 * @param asset - The asset being processed when the error occurred
 * @returns Promise resolving to enhanced error with additional context
 */
export async function babelErrorEnhancer(
  error: BabelError,
  asset: BaseAsset
): Promise<BabelError>;

interface BabelError extends Error {
  loc?: {
    line: number;     // Line number where error occurred
    column: number;   // Column number where error occurred
  };
  source?: string;    // Source code content (added by enhancer)
  filePath?: string;  // File path where error occurred (added by enhancer)
}

Error Message Cleaning

The enhancer improves error message readability by removing redundant information:

// Error message processing logic
if (error.loc) {
  // Remove file path prefix if present to avoid duplication
  let start = error.message.startsWith(asset.filePath)
    ? asset.filePath.length + 1  // Skip path and separator
    : 0;
  
  // Extract clean error message (first line only)
  error.message = error.message.slice(start).split('\n')[0].trim();
}

Before Enhancement:

/path/to/project/src/components/Button.jsx: Unexpected token, expected "}" (15:8)

After Enhancement:

Unexpected token, expected "}"

Source Context Addition

Adds complete source code and file path information for enhanced debugging:

// Source context enhancement
error.source = await asset.getCode();    // Full source code content
error.filePath = asset.filePath;         // Absolute file path

This allows error reporting tools and IDEs to:

  • Display source code context around the error
  • Provide accurate file navigation
  • Enable precise error highlighting
  • Support better stack trace generation

Error Types and Common Scenarios

Syntax Errors

Common JavaScript/TypeScript/JSX syntax errors enhanced with source context:

// Example: Missing closing brace
const Component = () => {
  return <div>Hello World</div>
  // Missing closing brace causes Babel error

Enhanced Error Information:

  • Message: "Unexpected token, expected '}'"
  • Location: { line: 3, column: 1 }
  • Source: Complete file content
  • FilePath: Absolute path to component file

Transform Plugin Errors

Errors from Babel plugins during transformation:

// Example: TypeScript transformation error
interface Props {
  invalid syntax here
}

Enhanced Error Information:

  • Message: "Unexpected token"
  • Location: Line and column of syntax error
  • Source: Full TypeScript source
  • FilePath: Path to TypeScript file

Configuration Errors

Errors related to Babel configuration or plugin setup:

// Example: Invalid preset configuration
{
  "presets": [
    ["@babel/preset-env", { invalidOption: true }]
  ]
}

Enhanced Error Information:

  • Message: "Unknown option: invalidOption"
  • Location: May not have specific location
  • Source: Configuration file content or processed source
  • FilePath: Path to file being processed

Integration with Parcel Error System

The enhanced errors integrate seamlessly with Parcel's diagnostic system:

// Usage in transformer
try {
  await babel7({
    asset,
    options,
    logger,
    babelOptions: config,
    tracer
  });
} catch (error) {
  // Enhance error before throwing
  throw await babelErrorEnhancer(error, asset);
}

Error Enhancement Process

  1. Error Interception: Catch original Babel error
  2. Message Cleaning: Remove redundant path information
  3. Source Addition: Add complete source code context
  4. Path Addition: Add absolute file path for navigation
  5. Error Propagation: Re-throw enhanced error for Parcel handling

Error Context Examples

Before Enhancement

// Original Babel error
{
  name: 'SyntaxError',
  message: '/Users/dev/project/src/Button.jsx: Unexpected token (15:8)\n\n  13 |   return (\n  14 |     <div className="button"\n> 15 |       onClick={handleClick\n     |                        ^\n  16 |     >\n  17 |       {children}\n  18 |     </div>',
  loc: { line: 15, column: 8 }
}

After Enhancement

// Enhanced error with context
{
  name: 'SyntaxError',
  message: 'Unexpected token',
  loc: { line: 15, column: 8 },
  source: 'import React from "react";\n\nconst Button = ({ onClick, children }) => {\n  const handleClick = () => {\n    onClick?.();\n  };\n\n  return (\n    <div className="button"\n      onClick={handleClick\n    >\n      {children}\n    </div>\n  );\n};\n\nexport default Button;',
  filePath: '/Users/dev/project/src/Button.jsx'
}

Benefits of Error Enhancement

For Developers

  • Cleaner Messages: Removes redundant file path information
  • Source Context: Complete source code for debugging
  • Precise Location: Accurate line and column information
  • Better Navigation: Absolute file paths for IDE integration

For Tools and IDEs

  • Rich Context: Full source code for syntax highlighting
  • Accurate Positioning: Precise error location mapping
  • File Navigation: Direct links to problematic files
  • Stack Trace Enhancement: Better error reporting in development tools

For Parcel Integration

  • Consistent Format: Standardized error structure
  • Enhanced Diagnostics: Better error reporting in build output
  • Source Map Support: Compatible with source map error mapping
  • Development Experience: Improved error messages in watch mode

Usage Example:

// Internal error enhancement flow
try {
  // Babel transformation attempt
  const result = await babelCore.transformAsync(sourceCode, config);
} catch (originalError) {
  // Enhance error with source context
  const enhancedError = await babelErrorEnhancer(originalError, asset);
  
  // Enhanced error now contains:
  console.log(enhancedError.message);    // Clean error message
  console.log(enhancedError.loc);        // { line: 15, column: 8 }
  console.log(enhancedError.source);     // Complete source code
  console.log(enhancedError.filePath);   // Absolute file path
  
  // Throw enhanced error for Parcel to handle
  throw enhancedError;
}

Install with Tessl CLI

npx tessl i tessl/npm-parcel--transformer-babel

docs

babel-processing.md

configuration.md

error-handling.md

index.md

transformer.md

utilities.md

tile.json