Selecting implementation attributes from interfaces about elm-graphql HOT 2 OPEN

Hey @Hazelfire, thanks for the discussion. I see what you're saying there, that's an interesting point.

I think you're right that the selectFromCourse type signature would be one way to support that.

Another idea, though a much more drastic change, would be to use Records as the Phantom Types. So taking this example from the Star Wars API example, since I'm looking at this source code in the examples folder for this one:

What if it was something like this:

-- in Swapi.Interface.Character
name : SelectionSet String { objectHuman : () }
name =
    Object.selectionForField "String" "name" [] Decode.string

-- in Swapi.Interface.Character
name : SelectionSet String { interfaceCharacter : (), objectHuman : (), objectDroid : () }
name =
    Object.selectionForField "String" "name" [] Decode.string

hero :
    (HeroOptionalArguments -> HeroOptionalArguments)
    -> SelectionSet decodesTo { character | interfaceCharacter : () }
    -> SelectionSet decodesTo RootQuery

This would allow you to have

Benefits of Record Approach

This is lightweight in a few ways.

1. You can intermix things that need the name field as part of a Character interface, or as part of one of its Object implementors (Droid or Human)
2. No import needed for the named types (Swapi.Interface.Character, etc.) - they are just records now, so they're structurally typed rather than nominally typed

Downsides of Record Approach

1. Is it more cumbersome or confusing to have these records rather than named types?
2. More type variables in a few places. Could that be confusing for some users? Could that be cumbersome at all in any cases even for users who are familiar with that technique?
3. In an API with a ton of types, this could become unwieldy. For example, the Node type in GitHub has almost 80 different implementors:

   elm-graphql/examples/src/Github/Interface/Node.elm

   Lines 23 to 102 in 8dcf2b4

   	{ onAddedToProjectEvent : SelectionSet decodesTo Github.Object.AddedToProjectEvent
   	, onAssignedEvent : SelectionSet decodesTo Github.Object.AssignedEvent
   	, onBaseRefChangedEvent : SelectionSet decodesTo Github.Object.BaseRefChangedEvent
   	, onBaseRefForcePushedEvent : SelectionSet decodesTo Github.Object.BaseRefForcePushedEvent
   	, onBlob : SelectionSet decodesTo Github.Object.Blob
   	, onBot : SelectionSet decodesTo Github.Object.Bot
   	, onClosedEvent : SelectionSet decodesTo Github.Object.ClosedEvent
   	, onCommentDeletedEvent : SelectionSet decodesTo Github.Object.CommentDeletedEvent
   	, onCommit : SelectionSet decodesTo Github.Object.Commit
   	, onCommitComment : SelectionSet decodesTo Github.Object.CommitComment
   	, onCommitCommentThread : SelectionSet decodesTo Github.Object.CommitCommentThread
   	, onConvertedNoteToIssueEvent : SelectionSet decodesTo Github.Object.ConvertedNoteToIssueEvent
   	, onCrossReferencedEvent : SelectionSet decodesTo Github.Object.CrossReferencedEvent
   	, onDemilestonedEvent : SelectionSet decodesTo Github.Object.DemilestonedEvent
   	, onDeployKey : SelectionSet decodesTo Github.Object.DeployKey
   	, onDeployedEvent : SelectionSet decodesTo Github.Object.DeployedEvent
   	, onDeployment : SelectionSet decodesTo Github.Object.Deployment
   	, onDeploymentStatus : SelectionSet decodesTo Github.Object.DeploymentStatus
   	, onExternalIdentity : SelectionSet decodesTo Github.Object.ExternalIdentity
   	, onGist : SelectionSet decodesTo Github.Object.Gist
   	, onGistComment : SelectionSet decodesTo Github.Object.GistComment
   	, onHeadRefDeletedEvent : SelectionSet decodesTo Github.Object.HeadRefDeletedEvent
   	, onHeadRefForcePushedEvent : SelectionSet decodesTo Github.Object.HeadRefForcePushedEvent
   	, onHeadRefRestoredEvent : SelectionSet decodesTo Github.Object.HeadRefRestoredEvent
   	, onIssue : SelectionSet decodesTo Github.Object.Issue
   	, onIssueComment : SelectionSet decodesTo Github.Object.IssueComment
   	, onLabel : SelectionSet decodesTo Github.Object.Label
   	, onLabeledEvent : SelectionSet decodesTo Github.Object.LabeledEvent
   	, onLanguage : SelectionSet decodesTo Github.Object.Language
   	, onLockedEvent : SelectionSet decodesTo Github.Object.LockedEvent
   	, onMarketplaceListing : SelectionSet decodesTo Github.Object.MarketplaceListing
   	, onMentionedEvent : SelectionSet decodesTo Github.Object.MentionedEvent
   	, onMergedEvent : SelectionSet decodesTo Github.Object.MergedEvent
   	, onMilestone : SelectionSet decodesTo Github.Object.Milestone
   	, onMilestonedEvent : SelectionSet decodesTo Github.Object.MilestonedEvent
   	, onMovedColumnsInProjectEvent : SelectionSet decodesTo Github.Object.MovedColumnsInProjectEvent
   	, onOrganization : SelectionSet decodesTo Github.Object.Organization
   	, onOrganizationIdentityProvider : SelectionSet decodesTo Github.Object.OrganizationIdentityProvider
   	, onOrganizationInvitation : SelectionSet decodesTo Github.Object.OrganizationInvitation
   	, onProject : SelectionSet decodesTo Github.Object.Project
   	, onProjectCard : SelectionSet decodesTo Github.Object.ProjectCard
   	, onProjectColumn : SelectionSet decodesTo Github.Object.ProjectColumn
   	, onProtectedBranch : SelectionSet decodesTo Github.Object.ProtectedBranch
   	, onPublicKey : SelectionSet decodesTo Github.Object.PublicKey
   	, onPullRequest : SelectionSet decodesTo Github.Object.PullRequest
   	, onPullRequestCommit : SelectionSet decodesTo Github.Object.PullRequestCommit
   	, onPullRequestReview : SelectionSet decodesTo Github.Object.PullRequestReview
   	, onPullRequestReviewComment : SelectionSet decodesTo Github.Object.PullRequestReviewComment
   	, onPullRequestReviewThread : SelectionSet decodesTo Github.Object.PullRequestReviewThread
   	, onPushAllowance : SelectionSet decodesTo Github.Object.PushAllowance
   	, onReaction : SelectionSet decodesTo Github.Object.Reaction
   	, onRef : SelectionSet decodesTo Github.Object.Ref
   	, onReferencedEvent : SelectionSet decodesTo Github.Object.ReferencedEvent
   	, onRelease : SelectionSet decodesTo Github.Object.Release
   	, onReleaseAsset : SelectionSet decodesTo Github.Object.ReleaseAsset
   	, onRemovedFromProjectEvent : SelectionSet decodesTo Github.Object.RemovedFromProjectEvent
   	, onRenamedTitleEvent : SelectionSet decodesTo Github.Object.RenamedTitleEvent
   	, onReopenedEvent : SelectionSet decodesTo Github.Object.ReopenedEvent
   	, onRepository : SelectionSet decodesTo Github.Object.Repository
   	, onRepositoryInvitation : SelectionSet decodesTo Github.Object.RepositoryInvitation
   	, onRepositoryTopic : SelectionSet decodesTo Github.Object.RepositoryTopic
   	, onReviewDismissalAllowance : SelectionSet decodesTo Github.Object.ReviewDismissalAllowance
   	, onReviewDismissedEvent : SelectionSet decodesTo Github.Object.ReviewDismissedEvent
   	, onReviewRequest : SelectionSet decodesTo Github.Object.ReviewRequest
   	, onReviewRequestRemovedEvent : SelectionSet decodesTo Github.Object.ReviewRequestRemovedEvent
   	, onReviewRequestedEvent : SelectionSet decodesTo Github.Object.ReviewRequestedEvent
   	, onStatus : SelectionSet decodesTo Github.Object.Status
   	, onStatusContext : SelectionSet decodesTo Github.Object.StatusContext
   	, onSubscribedEvent : SelectionSet decodesTo Github.Object.SubscribedEvent
   	, onTag : SelectionSet decodesTo Github.Object.Tag
   	, onTeam : SelectionSet decodesTo Github.Object.Team
   	, onTopic : SelectionSet decodesTo Github.Object.Topic
   	, onTree : SelectionSet decodesTo Github.Object.Tree
   	, onUnassignedEvent : SelectionSet decodesTo Github.Object.UnassignedEvent
   	, onUnlabeledEvent : SelectionSet decodesTo Github.Object.UnlabeledEvent
   	, onUnlockedEvent : SelectionSet decodesTo Github.Object.UnlockedEvent
   	, onUnsubscribedEvent : SelectionSet decodesTo Github.Object.UnsubscribedEvent
   	, onUser : SelectionSet decodesTo Github.Object.User
   	, onUserContentEdit : SelectionSet decodesTo Github.Object.UserContentEdit
   	}

   - these could be given type aliases easily, so maybe that would be fine?

Thoughts

Anyway, just throwing an idea out there, still need to think on it a little to decide if it's good or not. But seems like it might be worth considering that direction more seriously.

from elm-graphql.

I've come back to this several times, trying to understand what you mean and how it could be implemented.
The fact that I still don't understand it is a bit of a concern.

I think I get the general idea, but I do think that it might be a bit too on the nose of what's possible, and a much simpler implementation with much more obvious ways to do this might be preferable, at least in my eyes.

from elm-graphql.