Design System Peer Dependencies

Design system peer dependencies are packages that consuming applications must provide rather than receiving from the design system itself. Peer dependency decisions significantly impact adoption by determining compatibility requirements and potential installation friction.

What Are Peer Dependencies

Peer dependencies specify that a package works alongside rather than includes certain dependencies. For design systems, this commonly applies to framework packages like React, Vue, or Angular. Rather than bundling React, a React-based design system declares React as a peer dependency, expecting consuming applications to provide it.

Peer dependencies enable multiple packages to share single dependency instances. Without peer dependencies, each design system component might bring its own React copy, causing version conflicts and bundle bloat. Peer dependencies ensure the consuming application’s React version is used consistently.

How to Handle Peer Dependencies

Choosing what becomes a peer dependency requires judgment. Core frameworks should typically be peer dependencies. Utility libraries used internally might be direct dependencies if consumers are unlikely to need them. Commonly used libraries might go either way depending on whether version coordination with consumers matters.

Version range specification affects compatibility. Narrow ranges (exact versions or patch-only) maximize consistency but may conflict with consumer versions. Wide ranges (major version flexibility) maximize compatibility but may expose compatibility issues across versions. Testing across the supported range helps ensure stated compatibility is real.

Documentation should clearly list peer dependencies and their version requirements. Installation instructions should specify how to install peer dependencies. Troubleshooting guidance should address common peer dependency issues.

Error handling for missing peer dependencies improves user experience. Clear error messages when peer dependencies are missing or incompatible guide users toward resolution. Runtime checks can validate peer dependency presence during development.

Key Considerations

• Peer dependency changes may be breaking changes for consumers
• Testing against multiple peer dependency versions validates stated ranges
• Peer dependency version requirements should stay current with ecosystem support
• Too many peer dependencies creates installation burden
• Peer dependency errors can be confusing; good error messages help

Common Questions

How wide should peer dependency version ranges be?

Version range width involves trade-offs. Wider ranges improve compatibility but require more testing and may expose edge cases with specific versions. Narrower ranges reduce testing burden but may conflict with consumer versions. A common approach specifies compatibility with the last several major versions of key dependencies while maintaining active testing for those versions.

What should teams do when peer dependency conflicts arise?

Conflict resolution depends on the specific conflict. Sometimes consuming projects can update their versions to match requirements. Sometimes the design system can widen its version range if compatibility exists. Sometimes conflicts are fundamental and require workarounds like aliasing or isolation. Documenting common conflicts and resolutions helps users encountering these issues.

Summary

Design system peer dependencies specify packages consumers must provide rather than the design system bundling. Thoughtful peer dependency decisions consider what should be shared, appropriate version ranges, clear documentation, and helpful error handling. Managing peer dependencies well reduces installation friction and version conflicts.