How to Ignore External Library from NGCC Node

Managing external libraries in Angular can sometimes be a challenging task, especially when NGCC (Angular Compatibility Compiler) attempts to process third-party dependencies unnecessarily. In this guide, we’ll walk through how to effectively ignore external libraries in NGCC and optimize your development workflow.

Introduction

What is NGCC?

The Angular Compatibility Compiler (NGCC) is a tool in Angular that processes Node.js libraries to make them compatible with Ivy, Angular’s next-generation rendering pipeline. This step is essential for ensuring third-party packages work seamlessly in Angular projects.

Why Ignore External Libraries in NGCC?

Sometimes, NGCC may process libraries that do not require compilation or are already optimized. Ignoring these libraries can save time during builds, reduce errors, and improve performance.

The Role of NGCC in Angular

Angular Compatibility Compiler Explained

NGCC translates packages compiled with Angular View Engine into Ivy-compatible format. This ensures backward compatibility and a smoother transition for developers using older libraries.

Benefits of Using NGCC

• Enables compatibility with legacy libraries.
• Ensures Ivy-based rendering works as intended.
• Enhances performance for Angular apps.

Common Issues with NGCC and External Libraries

• Unexpected build failures.
• Long compilation times for unnecessary libraries.
• Errors due to misconfigured third-party dependencies.

When Should You Ignore External Libraries?

Scenarios to Avoid NGCC Compilation

• The library is already Ivy-compatible.
• The library is not used directly in the application.
• NGCC causes conflicts or errors with specific packages.

Impact of Ignoring External Libraries

Ignoring a library prevents NGCC from processing it, but ensure it doesn’t lead to missing functionalities or runtime errors.

Steps to Ignore an External Library

Updating angular.json

You can add the library to the allowedCommonJsDependencies section in your angular.json file to bypass specific warnings.

Using the ngcc.config.js File

1. Create or update the ngcc.config.js file in the root of your project.
2. Add the library to the ignores list:javascriptCopy codemodule.exports = { packages: { 'library-name': { entryPoints: { '.': { ignore: true } } } } };

Setting up a Custom Configuration

Customize the build script in your package.json to exclude unnecessary libraries:

jsonCopy code"scripts": {
  "postinstall": "ngcc --properties es2015 browser module main --first-only"
}

Example Configuration

Ignoring a Specific Library

Here’s how you can configure NGCC to skip processing example-library:

1. Add the following to ngcc.config.js:javascriptCopy codemodule.exports = { packages: { 'example-library': { entryPoints: { '.': { ignore: true } } } } };

Validating the Configuration

After updating, run:

bashCopy codengcc --validate

This ensures no errors are introduced.

Debugging Issues

Common Errors When Ignoring Libraries

• “Module not found” errors.
• Runtime issues due to missing dependencies.

How to Troubleshoot

• Double-check your ngcc.config.js file for typos.
• Use verbose logging during NGCC compilation:bashCopy codengcc --loglevel debug

Best Practices

Avoid Overlooking Dependencies

Ensure that ignored libraries do not have unresolved dependencies.

Testing Your Application

Run end-to-end tests after excluding libraries to ensure stability.

Advanced Techniques

Using Build Tools to Exclude Libraries

Tools like Webpack can be configured to bypass specific modules using the externals property.

Custom NGCC Compilation

You can customize NGCC execution for specific environments, like staging or production.

Advantages and Disadvantages

Pros of Ignoring External Libraries

• Faster build times.
• Reduced risk of unnecessary conflicts.

Cons to Consider

• Potential runtime issues.
• Missed updates for compatibility fixes.

Frequently Used Libraries to Ignore

List of Common Libraries

• @angular/compiler-cli
• rxjs
• zone.js

Community Recommendations

Join Angular forums or GitHub discussions to learn about libraries that others exclude.

Conclusion

Key Takeaways

Ignoring external libraries in NGCC can significantly improve build times and reduce conflicts. However, careful planning and testing are essential to ensure app stability.

Final Recommendations

Use ngcc.config.js wisely, and always test your app thoroughly after making changes.

FAQs

Q1: Can I safely ignore all third-party libraries in NGCC?
No, only ignore libraries that are confirmed Ivy-compatible or not required.

Q2: Is there any performance hit when ignoring libraries?
Yes, but only if the library needs processing for compatibility.

Q3: How do I revert back after ignoring a library?
Remove the library from the ngcc.config.js ignore list and rerun NGCC.

Q4: What if the ignored library is crucial for my app?
Avoid ignoring libraries that are critical for app functionality.

Q5: Are there any automation tools for managing NGCC exclusions?
Yes, tools like NX and custom scripts can help automate the process.