Provide an optional parameter for inferring @action/@computed/@observable

[rrousselGit]

This proposal is for automatically inferring @action/@computed/@observable based on the type of the variable.

The idea is, by letting the inference do its job, silly mistakes where we forgot to decorate a member can be stopped.

The inference would work using the following rules:

• private/protected members, whatever their type is, don't benefit from inferred decorators.
• public getters are inferred as @computed
• public mutable property as inferred as @obvervable
• public immutable properties aren't @observable
• public methods are inferred as @action

This inference can be configured using two different ways:

• using @Store decorator, for store specific override

  @Store(
  autoComputed: true,
  autoAction: true,
  autoObservable: true,
  )
  class MyStore { ... } 

• inside the build.yaml file, for global configuration change:

  targets:
  $default:
    builders:
      mobx_codegen:
        options:
          autoComputed: true
          autoAction: true
          autoObservable: true

---

I've looked through the entire mobx_examples folder and all of the examples follows these rules.

There are some exceptions, like in form_store.dart where setupValidations is not decorated. But setupValidations should probably be performed inside the constructor of FormStore and therefore setupValidations can be made private.

Another exception is in github_store.dart, where repositories is not @obvervable. But that seems dangerous considering repositories is mutated on multiple occasions and is used inside the build method of RepositoryListView.

[eltonomicon]

I like the @store attribute with optional parameters to enable inference. Comments:

• If you want to infer, I think the high % case would be to infer all 3. I think it would be best to have an option to infer all 3 with 1 parameter instead of having to always specify 3 parameters.
• 'public getters are inferred as @computed' seems to conflict with 'public immutable properties aren't @observable'. Also IMO there is a case for observable readonly properties, see #220, although maybe this isn't an inference use case.

Would inference be all-or-nothing or could you still use annotations to override inference rules?

[pavanpodila]

Great idea @rrousselGit. Overall I like the direction. Few other things to consider:

• The defaults should be false I think, in order to avoid an collisions with the original intents of the Store class. Not all getter functions are computed (as @eltonomicon pointed out), not all props are observables by default.
• There should be a way to turn off the auto-generation for some props (eg @noAction, @noComputed, @noObservable). Essentially a per-member toggle that can be used to opt out of the auto generation.

[smiLLe]

@pavanpodila you often see ignore: true . so for computed it would be @computed(ignore: true)

[eltonomicon]

Agreed with ignore: true, IMO this is preferable to doubling the number of annotations.

[pavanpodila]

Ya like the ignore approach.

[rrousselGit]

It should be @Computed() in that case.

Anyway I agree with ignore. If peoples wants a shorthand to make it easier to use, they can do the following:

const noComputed = Computed(ignore: true);

[pavanpodila]

@shyndman I was thinking we can pick this up as a good enhancement for simplifying the use of MobX for most users. The current @store directive can get a nitro-boost with this auto-inference feature? What do you think ?

[shyndman]

Yeah, I'm into it, along with the opt-out annotation.

Maybe we could generalize the opt-outs into a single annotation? Something like @ignore()?

[pavanpodila]

I prefer the @ignore approach On 27 Dec 2019, 1:21 AM +0530, Scott Hyndman notifications@github.com, wrote:

Yeah, I'm into it, along with the opt-out annotations. Maybe we could generalize the opt-outs into a single annotation? Something like @ignore()? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or unsubscribe.