When upgrading Angular 5 to 6, I get incompatible peer dependency (using ng update @angular/core)

2 min read 06-10-2024

When upgrading Angular 5 to 6, I get incompatible peer dependency (using ng update @angular/core)

"Incompatibilities" Galore: Troubleshooting Angular 5 to 6 Upgrade Issues

Upgrading Angular versions can be a necessary step for accessing new features and improving your application's performance. However, it often comes with the dreaded "incompatible peer dependency" error message. This article dives into the common reasons behind this error during an Angular 5 to 6 upgrade, particularly when using ng update @angular/core.

Understanding the Issue

In simple terms, "incompatible peer dependency" means that a library your project uses (like @angular/core) requires a different version of another library (like rxjs) than the one you currently have installed. This conflict prevents the upgrade process from succeeding.

The Scenario and the Code

Imagine you have an Angular 5 application with the following package.json snippet:

"dependencies": {
  "@angular/core": "^5.2.11",
  "rxjs": "^5.5.11",
  ...
}

You execute ng update @angular/core to upgrade to Angular 6, but the command fails with the error:

"Incompatible peer dependency: rxjs@^6.0.0"

Unpacking the Error: Analyzing the Problem

This error message tells us that Angular 6 (or a package it depends on) requires a version of rxjs starting from version 6.0.0, while your project currently has version 5.5.11. This conflict needs to be resolved to proceed with the upgrade.

Solutions: Resolving the Incompatible Dependencies

Directly Update rxjs: The most straightforward solution is to update rxjs to a compatible version using npm install [email protected]. You can choose the latest version of rxjs compatible with Angular 6.
Update Other Dependencies: Sometimes, upgrading rxjs alone isn't enough. You might also need to update other packages that have their own peer dependency issues. The ng update command often provides suggestions about additional packages that need updating.
Use a Package Manager: Using a package manager like yarn or npm can help manage dependency conflicts more effectively. If you're not already using one, consider switching to either of them.

Proactive Measures: Preventing Future Conflicts

Use Semantic Versioning (Semver): Understand and utilize the semver notation (^, ~, *) in your package.json to control how your dependencies are updated.
Monitor Dependency Updates: Regularly check for updates to your project's dependencies.
Test Before Deployment: Always test your application after any dependency upgrade to ensure compatibility.

Additional Value: Beyond the Error Message

Understanding Peer Dependencies: Peer dependencies are essential for library authors to define compatibility with other libraries used within a project. They ensure that different components work seamlessly together.
Using ng update Effectively: The ng update command is powerful and helpful but remember to carefully review any warnings or error messages to understand the necessary steps for a successful upgrade.

Conclusion: A Smooth Upgrade Journey

Upgrading Angular versions is inevitable. By understanding the root of "incompatible peer dependency" errors and adopting a proactive approach to dependency management, you can minimize the potential for issues and enjoy a smooth upgrade process. Remember to test thoroughly after any updates, and always refer to the Angular documentation and community resources for the latest best practices.

References: