Peer Dependencies

Peer dependencies on jspm follow the same principle as npm - that there can only be one version of a peer dependency package in jspm.

The way jspm handles this is by:

  • Installing the peer dependency into the base-level SystemJS map configuration as if it had been installed as a primary dependency in the first place.
  • Adding the peer dependency itself to the package.json peerDependencies property of the app. This way every app that installs a peer dependency manages the install constraints of that peer dependency itself.
  • Peer dependency conflicts happen when one package expects the peer dependency to be installed to one range (say npm:[email protected]^0.14.0), while another package expects the peer dependency to be installed to another (like npm:[email protected]~0.13.2).
  • Whenever there is a peer dependency conflict, a prompt is provided to select the correct resolution range to install the dependency to. In this way peer dependencies never error in jspm, but may not work when out of range. Think of it just like traditional package management without encapsulated multi-version support.

To demonstrate the conflict resolution, let's set up exactly the scenario above.

First uninstall our published component which will provide the conflict:

jspm uninstall jspm-react-component-demo

Then install React to an invalid peer range:

jspm install npm:[email protected]~0.14 --peer

Now if we install the published component that has a peer dependency on npm:[email protected]:

jspm install npm:jspm-react-component-demo

the peer dependency conflict resolution prompt is displayed:

     Updating registry cache...

     Peer dependency conflict for react:
       Currently installed as npm:[email protected]
       Package npm:[email protected] requires npm:[email protected]^15.1.0.

Would you like to install react to the new install range? [Yes]:

If we select the default Yes option, we upgrade to React 15.1.0 and the remaining install runs smoothly.

Alternatively, if we enter No, we get the following prompt:

Would you like to retain the current resolution? [Yes]:

If we select No again we then get:

Enter a custom package resolution range:

We can now enter any install target, even something like npm:[email protected].