Multiple Version Instances

Multiple version instances occur when the same package is installed at different versions within a project’s dependency tree. While package managers support this to resolve version conflicts, it can cause problems for packages expecting to be singletons. Design systems often encounter this with framework dependencies and shared utilities.

What Are Multiple Version Instances

Multiple version instances means having more than one copy of a package installed, each at a different version. This happens when different packages in the dependency tree require incompatible versions. Package managers install both versions in different node_modules locations.

For example, a project might have React 17 at the top level and React 18 nested inside a dependency. Code in different locations may see different React versions, causing inconsistencies.

How Multiple Version Instances Work

Understanding how multiple versions arise and their effects helps prevent and diagnose related issues.

Installation causes multiple versions when requirements conflict. If design-system@1.0 requires dependency@^1.0 and design-system@2.0 requires dependency@^2.0, installing both design system versions results in two dependency versions.

Node modules structure accommodates multiple versions. npm hoists what it can to the top level but nests conflicting versions within the requiring package’s node_modules. This allows different packages to use their required versions.

Import resolution determines which version code receives. Node’s module resolution algorithm finds packages by traversing up the directory tree. Code sees the first matching package in its resolution path. Different code may resolve to different versions.

Singleton packages malfunction with duplicates. React, for instance, expects a single instance. Multiple React versions cause hooks to fail, context to not propagate, and state to become inconsistent. These bugs are often confusing because they appear unrelated to versioning.

Key Considerations

• Peer dependencies help prevent framework duplication
• Bundle analyzers reveal duplicate packages
• Version alignment across packages reduces duplication
• Resolutions can force single versions when appropriate
• Testing with production bundle conditions catches issues

Common Questions

How can multiple version instances be detected?

Several methods reveal when packages have been duplicated across versions. Regular detection helps catch issues before they cause runtime problems.

npm ls shows the dependency tree including duplicates. Running npm ls package-name reveals all installations of a package. Multiple listings at different versions indicate duplication.

Bundle analyzers visualize duplicates. Tools like webpack-bundle-analyzer, source-map-explorer, or bundle-buddy show package duplicates in built bundles. These tools reveal the bundle size impact of duplication.

Lock file inspection shows installed versions. Searching package-lock.json for a package name reveals all resolved versions. Multiple entries suggest potential duplication.

Runtime detection using package version can confirm suspicions. Logging the version of a package in different parts of the application reveals if different code sees different versions.

How can design systems prevent causing duplicate installations?

Design system packages should be structured to minimize duplication risk in consumer projects. Several practices help.

Use peer dependencies for shared packages. Making React a peer dependency rather than a regular dependency prevents the design system from bundling its own React. Consumers provide React, ensuring a single version.

Maintain broad peer dependency ranges. Supporting multiple major versions of frameworks (^17.0.0 || ^18.0.0) lets consumers use their preferred version without conflicts.

Minimize internal dependencies. Each dependency the design system includes is a potential duplication point. Evaluating whether dependencies are truly necessary reduces risk.

Test in consumer-like conditions. Running design system code in environments simulating consumer setups, rather than just within the monorepo, reveals duplication issues before release.

Externalize framework code in builds. Build configurations should externalize peer dependencies rather than bundling them. This ensures consumers’ versions are used.

Summary

Multiple version instances occur when packages are installed at different versions within a dependency tree. While package managers support this, it causes problems for singleton packages like React. Peer dependencies, broad version ranges, and consumer-like testing help design systems prevent causing duplication in consumer projects.