Optional Non-installed Dependencies

[fishcharlie]

What / Why

It would be great instead of optionalDependencies in the package.json options, if there was an option just like optionalDependencies but that the package wouldn't be installed by default. This would be especially useful for things like the debug npm package. An example of this would be, I want users to be able to use debug and get information provided by it from my NPM package, but not all users will need to take advantage of that debug functionality, so it shouldn't be installed by default, and should be completely optional.

When

• n/a

Where

• npm/cli

How

Current Behavior

• optionalDependencies installs automatically

Expected Behavior

• Option to mark optionalDependency as not installed automatically, it'd be great if the CLI alerted users that these are additional packages that can be installed manually for more functionality.

Who

• n/a

References

• n/a

[ljharb]

I believe you can already do this with peer deps + peerDependenciesMeta?

[fishcharlie]

@ljharb Any documentation on that? All I see is info for peerDependencies under the package.json docs. Looks more like for use with plugins, I'm not sure if that is the same use case as what I'm trying to do. But maybe adding peerDependenciesMeta gives more flexibility? But never heard of the peerDependenciesMeta option before.

[abdonrd]

I have created an issue about document the peerDependenciesMeta property: #1247

[remyrylan]

For anyone stumbling on this same problem, peerDependencies + marking as optional using peerDependenciesMeta still automatically installs and is not currently a solution.

I've opened an issue here to discuss: npm/rfcs#221

[remyrylan]

@fishcharlie fyi, this was implemented here: npm/arborist@e13ba3b and I presume it will be in the next npm v7 beta, but that's up to the npm team.

It relies on using the peerDependenciesMeta field, paired with { "optional": true }.

Example package.json:

{
  "peerDependencies": {
     "react": "^16.0.0"
  },
  "peerDependenciesMeta": {
     "react": {
        "optional": true
     }
  }

In this case, react will not be automatically installed.