Common Issues in Rollup

Rollup-related problems often stem from incorrect configuration, unresolved dependencies, plugin misconfigurations, and scope hoisting limitations. Identifying and resolving these challenges improves build stability and performance.

Common Symptoms

• Build fails with syntax or dependency resolution errors.
• Unexpected output file size due to ineffective tree shaking.
• Plugin incompatibilities causing build process interruptions.
• ESM and CommonJS interoperability issues.

Root Causes and Architectural Implications

1. Build Failures Due to Configuration Errors

Incorrect rollup.config.js settings, missing input/output configurations, or incorrect plugin orders can cause build failures.

// Verify Rollup configuration
import { defineConfig } from "rollup";
import resolve from "@rollup/plugin-node-resolve";
import commonjs from "@rollup/plugin-commonjs";

export default defineConfig({
  input: "src/index.js",
  output: {
    file: "dist/bundle.js",
    format: "esm"
  },
  plugins: [resolve(), commonjs()]
});

2. Ineffective Tree Shaking

Unused code may still be included in the output bundle due to improper module imports or side-effectful dependencies.

# Enable verbose mode to debug tree shaking
rollup --config --verbose

3. Plugin Conflicts and Unexpected Errors

Some Rollup plugins may interfere with each other or require specific ordering.

# List installed plugins and versions
npm list | grep rollup

4. CommonJS and ES Module Interoperability Issues

Mixing CommonJS and ES modules without proper handling can cause import/export errors.

# Ensure @rollup/plugin-commonjs is included
npm install @rollup/plugin-commonjs

Step-by-Step Troubleshooting Guide

Step 1: Fix Build Configuration Errors

Ensure rollup.config.js has correctly defined input, output, and plugins.

# Validate Rollup configuration
node -c rollup.config.js

Step 2: Optimize Tree Shaking

Ensure ES modules are used correctly and unnecessary imports are removed.

# Verify tree shaking
rollup --config --debug

Step 3: Resolve Plugin Conflicts

Ensure plugins are installed in the correct order and avoid duplicates.

# Remove and reinstall plugins
npm remove @rollup/plugin-commonjs @rollup/plugin-node-resolve && npm install

Step 4: Fix CommonJS and ESM Compatibility Issues

Enable CommonJS support and ensure dependencies are properly bundled.

# Modify Rollup config to support CommonJS
import commonjs from "@rollup/plugin-commonjs";
export default {
  plugins: [commonjs()]
};

Step 5: Debug Output File Size and Performance

Analyze the output bundle to detect unused or oversized dependencies.

# Analyze bundle size
rollup --config --silent | grep "unused"

Conclusion

Optimizing Rollup builds requires proper configuration, efficient tree shaking, plugin management, and module compatibility handling. By following these best practices, developers can ensure faster and more efficient bundling processes.

FAQs

1. Why is my Rollup build failing?

Check rollup.config.js for syntax errors, ensure dependencies are installed, and validate plugin configurations.

2. How do I enable tree shaking in Rollup?

Ensure modules use ES exports and that side-effectful imports are marked properly in package.json.

3. Why are my Rollup plugins conflicting?

Ensure plugins are installed correctly, avoid duplicate plugins, and check plugin execution order.

4. How do I fix CommonJS and ES module compatibility?

Use @rollup/plugin-commonjs and ensure dependencies are properly resolved in node_modules.

5. How do I analyze Rollup bundle size?

Enable verbose mode and use rollup --config --silent to inspect unused modules and dependencies.