Support peer dependencies

[matanlurey]

From NPM: https://nodejs.org/en/blog/npm/peer-dependencies/

There is an increasing number of packages (built_*, json_*, angular, so others for Flutter) that require a specific dev_dependency range for compatible tooling/code generation. For example, the json_annotation package is platform agnostic, but requires the json_serializable package for code generation.

It would be nice to be able to write, in pubspec.yaml:

name: json_annotation

peer_dependencies:
  json_serializable: ^1.0.0

... so that, dev_dependencies on json_serializable are validated against this range.

/cc @kevmoo @mit-mit

[kevmoo]

Yes, please!

[cah4a]

Hey,

I'm developing nock package.
I think the correct way to describe the dependencies of such packages is to make a peer dependency to test package.

Is there any plans to implement peer dependencies support?

[sigurdm]

... looking through old issues.

A peer_dependency is a constraint on another package but doesn't require that other package to be included in the resolution?

Am I understanding this right?

What happens if you just make a regular dependency? Don't you always need json_serializable when you use json_annotation?

[cah4a]

Peer dependency is a dependency that a user should explicitly specify in a pubspec.

A good article about the corresponding npm feature here.

[kevmoo]

@sigurdm – you are correct. If you have a dependency on json_annotation you almost certainly want/need a dev_dependency on json_serializable

[sigurdm]

Peer dependency is a dependency that a user should explicitly specify in a pubspec.

Sorry I don't get this (might need more coffee). Can you spell out a scenario where a peer dependency solves a problem that a regular dependency wont (in the pub model where all dependencies are shared in a resolution).

[kevmoo]

@matanlurey was the original idea maker here. I may have lost the thread....

[uvlek]

It would be nice to have implementation of peer dependencies in flutter pubspec

[sigurdm]

@uvlek can you explain some scenarios where you would use them? I'm still unsure about what they exactly can help us with.

[github-actions]

Without additional information we're not able to resolve this issue, so it will be closed at this time. You're still free to add more info and respond to any questions above, though. We'll reopen the issue if you do. Thanks for your contribution!

[ZimboPro]

One way that I can think, working on a large project, having the project's features in there own packages to make the app more modular but 2 packages might depend on each other. This will cause a cyclic dependency which could be fixed by having the 2 features in the same package but then the issue is that both features need to be stable before release a new version of the package. Peer packages will allow the features to be in its own packages and allow for stability in the app.