Troubleshooting and Debugging

Bundlers

Troubleshooting and Debugging

Even though esbuild is designed to be fast and straightforward, you may encounter issues during the build process that require troubleshooting. In this section, we’ll cover common problems you might face, along with techniques for debugging and resolving these issues.

1. Common Issues and Their Solutions

Below are some common issues that developers might encounter when using esbuild and how to address them:

a. Build Fails with Syntax Errors

If esbuild encounters syntax errors in your code, it will fail to build and output an error message.

Example Error:

bash 
	✘ [ERROR] Expected ";" but found "}"
	src/index.js:10:1:
	   10 │ }
	      │  ^

Solution:

  • Review the file and line number indicated in the error message.
  • Ensure that your JavaScript/TypeScript code follows the correct syntax.
  • Use a linter like ESLint to catch syntax errors before running esbuild.

b. Import Errors (Cannot Find Module)

This error typically occurs when esbuild cannot locate the module you’re trying to import.

Example Error:

bash 
	✘ [ERROR] Could not resolve "some-module"
	src/index.js:3:19:
	    3 │ import something from "some-module";
	      │                    ~~~~~~~~~~~~~~~~

Solution:

  • Verify that the module is installed in your node_modules directory.
  • Ensure that the module name is spelled correctly and matches the exact case.
  • Check if the module requires a specific loader or plugin and configure esbuild accordingly.

c. Unexpected Output or Bundling Issues

Sometimes, the output generated by esbuild might not behave as expected, especially if there are complex dependencies or conditional imports.

Solution:

  • Review your esbuild configuration to ensure that all necessary options (e.g., loaders, plugins) are correctly set.
  • Simplify your entry points to isolate the issue by bundling individual files to identify the problematic module.
  • Use the external option to exclude certain modules from the bundle if they should be handled separately (e.g., Node.js built-in modules).
javascript 
	// Example: Exclude Node.js built-in modules
	
	esbuild
	  .build({
	    entryPoints: ['src/index.js'],
	    bundle: true,
	    external: ['fs', 'path'], // Exclude Node.js built-ins
	    outfile: 'dist/bundle.js'
	  })
	  .catch(() => process.exit(1));

d. Performance Issues

If you notice that your build times are slower than expected, there may be optimizations that can help.

Solution:

  • Ensure that incremental builds are enabled during development to speed up subsequent builds.
  • Review your usage of plugins—some plugins may introduce overhead. Use only the necessary plugins.
  • Use the define option to inject environment variables and avoid unnecessary transformations.

2. Debugging Techniques

When you run into issues with your esbuild setup, debugging is an essential skill. Here are some techniques to help you debug your build process:

a. Enable Detailed Logging

esbuild provides minimal logging by default. You can increase the verbosity of the output to help identify issues.

Example: Enable Detailed Logging

javascript 
	// build.js
	
	const esbuild = require('esbuild');
	
	esbuild
	  .build({
	    entryPoints: ['src/index.js'],
	    bundle: true,
	    logLevel: 'debug', // Enable detailed logging
	    outfile: 'dist/bundle.js'
	  })
	  .catch(() => process.exit(1));

The logLevel option can be set to 'info', 'warning', 'error', or 'debug', with 'debug' providing the most detailed output.

b. Isolate the Issue

When faced with a complex issue, try isolating parts of your build process to identify the root cause. This can involve:

  • Bundling only specific files or modules.
  • Removing plugins or configuration options one by one.
  • Running esbuild on a smaller subset of your codebase.

c. Inspect the Output Files

Inspect the generated bundle or output files to verify that the code looks as expected. Tools like source-map-explorer can help you analyze the contents of your bundle and identify any unexpected large dependencies or unused code.

d. Use a REPL for Quick Testing

If you’re debugging JavaScript code transformations or plugins, you can use Node.js’s REPL (Read-Eval-Print Loop) to test small snippets of code. This can help you quickly identify syntax errors or unexpected behavior in isolated environments.

bash 
	node

In the REPL, you can require modules and test transformations interactively.

3. Community Resources and Support

When troubleshooting complex issues, it can be helpful to consult the wider community. Here are some resources to consider:

  • esbuild GitHub Repository: The official esbuild repository is a good place to report bugs or search for existing issues that might be similar to yours.
  • Discussions and Forums: Platforms like Stack Overflow, Reddit, and the esbuild GitHub Discussions page can be valuable for finding solutions to common problems.
  • Documentation: Always refer to the official esbuild documentation for the latest updates, features, and configuration options.