Circular dependencies between models

[chrisdrackett]

I'm running into the following error on all my models that are related to each other:

'TagTypeModelBase' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.

Here is the file in question:

UserModel.base.ts

...
export const UserModelBase = MSTGQLObject
  .named('User')
  .props({
    __typename: types.optional(types.literal("User"), "User"),
    createdAt: types.maybe(types.frozen()),
    email: types.maybe(types.string),
    id: types.identifier,
    name: types.maybe(types.string),
    projects: types.optional(types.array(MSTGQLRef(types.late((): IAnyModelType => ProjectModel))), []),
    updatedAt: types.maybe(types.frozen()),
  })
...

Project has a link back to the User model. When I first ran into this I found:

https://github.com/mobxjs/mobx-state-tree#handle-circular-dependencies-between-files-and-types-using-late

and thought I could get around this by editing UserModel.ts like the following:

export const UserModel = UserModelBase.props({
  projects: types.optional(
    types.array(MSTGQLRef(types.late((): IAnyModelType => ProjectModel))),
    [],
  ),
})

But I still get the error in typescript. It seems like I need to edit UserModel.base.ts directly to fix this issue, but that is a generated file.

[Amareis]

+1, in my (complicated enough) domain models generated models are useless because of circular dependencies.

[Amareis]

Against the comment in https://github.com/mobxjs/mst-gql/blob/master/generator/generate.js#L354, types.late isn't enough to prevent circular dependencies :)

[elie222]

@chrisdrackett does editing the generated file solve your problems? (I realise this isn't a long term fix).

@Amareis is the problem with TS types or a JS issue?

[Amareis]

@elie222 just TS typings. For correct circular references handling we need to use types.late((): IAnyModelType => SomeModel), but if we do it everywhere, all references will be any type. So, this should be applied only at some points, to break the wheel, but currently IDK how to select that points algoritmically.

[Amareis]

https://github.com/pahen/madge can be helpful in find and resoving circular deps. My current models have 36 of it.

[chrisdrackett]

@elie222 editing the generated file does fix the problem, but like @Amareis mentioned because this makes the return type any you only want to do it where needed and not on everything. I'm not sure if that is something the library could detect, but if so, it would be awesome.

I can try and add a note about this if needed to the docs. Its really more a MST thing than a mst-gql thing, but might be worth letting users know about regardless.

[elie222]

So I'm thinking we can handle this by manually generating the TS types. TS shouldn't have issues with the circular dependencies in general. For example, the following code compiles fine:

interface Post {
  id: string
  comment?: Comment
}

interface Comment {
  id: string
  post: Post
}

const post: Post = {
  id: 'a',
  comment: {
    id: 'b',
    post: {
      id: 'c',
    }
  }
}

Having TS figure out the types from the model itself is nice usually, but as we're generating this code in any case, we may as well generate the TS types too and get around this circular any issue.

@mweststrate I know you've dealt with circular dependencies quite a lot. What are your thoughts on this?

[Amareis]

Yep, that's will really cool! Besides of circular deps handling, it'll make nice typenames in compiler errors, instead of usual mst types garbage.

[mweststrate]

I think it is a really cool idea! Be aware to use interfaces instead of types wherever possible, as types in TS can't have circular refs either

…

On Fri, Jul 12, 2019 at 12:30 PM Иван Плесских ***@***.***> wrote: Yep, that's will really cool! Besides of circular deps handling, it'll make nice typenames in compiler errors, instead of usual mst types garbage. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#45?email_source=notifications&email_token=AAN4NBGSB3PNVX6PFMYTPELP7BMM5A5CNFSM4H4LOAR2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODZZMGMQ#issuecomment-510837554>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAN4NBELEH6JNRCBMW6UNCLP7BMM5ANCNFSM4H4LOARQ> .

[mweststrate]

Regardless on whether the above is implemented or not, in general two tips that help with breaking circular type dependencies:

1. Break circles by not relying on type inference for method arguments / return types (example: Circular type references with TS 3.5 mobx-state-tree#1341 (comment))
2. Use interfaces that extends types (example: https://github.com/mobxjs/mobx-state-tree#using-a-mst-type-at-design-time, the second code snippet)

Hope that helps in the mean time!

[chrisdrackett]

@elie222 have you done any work on this? I was thinking of giving it a try tomorrow and/or over the weekend

[elie222]

I have not unfortunately :( too busy right now

…

On Fri, 26 Jul 2019 at 6:36 Chris Drackett ***@***.***> wrote: @elie222 <https://github.com/elie222> have you done any work on this? I was thinking of giving it a try tomorrow and/or over the weekend — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#45?email_source=notifications&email_token=AAXSQXY4A6D2LK2B2346BZ3QBJWMDA5CNFSM4H4LOAR2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD23MU3I#issuecomment-515295853>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAXSQX2KVTMW7PNKDNVOBYTQBJWMDANCNFSM4H4LOARQ> .