Allow integration with melos

[GZGavinZhao]

melos is another tool for managing mono repos. However, I feel that mono_repo is better when generating readable/debuggable CI config in the least amount of typing. Therefore, we decided to use both melos and mono_repo for our repo.

This, unfortunately, poses a problem: melos needs to be dart pub global activate-d and ran melos bootstrap to link local packages using the pubspec_overrides.yaml file. If not, then analyzing and testing might fail. mono_repo provides no way of running arbitrary commands at the start of each CI job.

I hope we can either allow defining commands to be run at the start of each job, or add a melos config to mono_repo.yaml. When set to true, it will add a step to activate and bootstrap melos before any user-defined commands are run.

I have already implemented the second option in a basic way. If accepted I'd be glad to further polish it!

[kevmoo]

I support better integration in principle. Figuring out the details is always fun, though.

CC @natebosch and @jakemac53

[jakemac53]

Personally I would suggest just creating your own script under tool, which invokes melos and then mono_repo?

If we did want to support something like this I would probably just support running arbitrary commands, we don't want to be picking up a dependency on the api of melos.

[natebosch]

we don't want to be picking up a dependency on the api of melos.

+1

would https://github.com/google/mono_repo.dart/pull/382 be sufficient to solve this use case?

[GZGavinZhao]

@natebosch Yes, #382 would be sufficient.

[blaugold]

I'm not very familiar with mono_repo so I've created an example repo to better understand how to integrate it with Melos.

It's possible to get it working with Melos, but it's not great:

# a/mono_pkg.yaml
sdk:
  - stable

stages:
  - analyze:
      - command:
          - 'dart pub global activate melos'
          - 'dart pub global run melos bootstrap --scope a'
          - 'dart analyze'
  - format:
      - command:
          - 'dart pub global activate melos'
          - 'dart pub global run melos bootstrap --scope a'
          - 'dart format --output=none --set-exit-if-changed .'
  - test:
      - command:
          - 'dart pub global activate melos'
          - 'dart pub global run melos bootstrap --scope a'
          - 'dart test'

I don't think #382 would help all that much, since you would have to configure Melos for every job, if I understand the intent of the PR correctly.

It would be optimal, if there was a way to replace the pub upgrade step with an arbitrary command. Even better, if the command gets the name of the current package in an environment variable.

If this was configurable in mono_repo.yaml for all jobs, it would make it really simple to set up Melos.

[kevmoo]

Yeah, having some template silly (like #382 ) would be nice. Not sure how much complexity we'd be adding...

[dnys1]

Would it make sense to expose TaskType.beforeAllSteps/TaskType.afterEachSteps, maybe via mono_repo.yaml, similar to how on_completion is exposed? My use case could also benefit from the lack of repetition. Another option would be to define a custom action in the repo and use #382, but that would lead to nearly the same amount of repetition, I think.