@Dependency property wrapper does not compile inside EntityQuery conforming struct

[twocentstudios]

Description

I'm trying to use the @Dependency property wrapper within a struct conforming to the EntityQuery protocol in the AppIntents framework. Currently I'm trying to define an EntityQuery in a widget extension.

I'm getting a compiler error on the @Dependency line in the struct body and within the init method: Type of expression is ambiguous without a type annotation.

Checklist

• I have determined whether this bug is also reproducible in a vanilla SwiftUI project.
• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue or discussion.

Expected behavior

The target compiles and I can use the resolved dependency.

Actual behavior

Compiler error: Type of expression is ambiguous without a type annotation (see code below)

Steps to reproduce

• Create new SwiftUI project
• Add a WidgetExtension
• Paste the following in the generated Widget.swift file

import AppIntents
import Dependencies

// No error; a struct non-conforming to EntityQuery compiles
public struct SimpleModel {
    @Dependency(\.exampleDependency) var db
}

// Setting up a minimal `AppEntity`/`EntityQuery` that uses an `ExampleDependency`
@DependencyClient struct ExampleDependency { }
extension ExampleDependency: DependencyKey {
    static var liveValue: ExampleDependency { .init() }
}
extension DependencyValues {
    var exampleDependency: ExampleDependency {
        get { self[ExampleDependency.self] }
        set { self[ExampleDependency.self] = newValue }
    }
}

public struct AppEntityConformingModel: AppEntity {
    public static var defaultQuery: AppEntityConformingModelQuery { AppEntityConformingModelQuery() }
    public static var typeDisplayRepresentation: TypeDisplayRepresentation = ""
    public var displayRepresentation: DisplayRepresentation { .init(stringLiteral: "") }
    public let id: String
}

// Trying 3 different strategies to use `@Dependency`
public struct AppEntityConformingModelQuery: EntityQuery {
    @Dependency(\.exampleDependency) var db // ERROR: Type of expression is ambiguous without a type annotation
    @Dependency(\.exampleDependency) var db: ExampleDependency // ERROR: Property type 'ExampleDependency' does not match 'wrappedValue' type '<<error type>>'

    public init() { 
        @Dependency(\.exampleDependency) var db // ERROR: Type of expression is ambiguous without a type annotation
    }
    public func entities(for identifiers: [AppEntityConformingModel.ID]) async throws -> [AppEntityConformingModel] { [] }
    public func suggestedEntities() async throws -> [AppEntityConformingModel] { [] }
    public func defaultResult() async -> AppEntityConformingModel? { nil }
}

For now, I think I can use the below workaround: using @Dependency in the defaultQuery property of the AppEntity and passing the results manually into the AppEntityConformingModelQuery initializer.

public struct AppEntityConformingModel: AppEntity {
    public static var defaultQuery: AppEntityConformingModelQuery {
        @Dependency(\.exampleDependency) var db
        return AppEntityConformingModelQuery(db: db)
    }
    // ...
}

Related docs for creating a configurable Widget that show minimal EntityQuery and AppEntity definitions: https://developer.apple.com/documentation/widgetkit/making-a-configurable-widget

Dependencies version information

main (3815c48) (near 1.3.1)

Destination operating system

iOS 17

Xcode version information

Version 15.4 (15F31d)

Swift Compiler version information

swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
Target: arm64-apple-macosx14.0

[mbrandonw]

Hi @twocentstudios, I believe this is because the AppIntents framework already has its own @Dependency property wrapper. Well, actually, they have a @AppDependency property wrapper, and then for some reason have a typealias Dependency = AppDependency, and there's not even any docs on it.

So unfortunately I believe this means you have to do:

@Dependencies.Dependency(\.key) var value

…when importing AppIntents.

I was under the impression that when there are conflicts between a user's code and Apple's libraries that you would be forced to qualify their APIs (e.g. @AppIntents.Dependency), but maybe that is only true of types in the standard library.

In any case, since this isn't an issue with the library I am going to convert it to a discussion. Please feel free to continue the conversation over there!

[twocentstudios]

Ah, that did the trick! Thanks 🙏

[Bartozo]

I was also wondering why it didn't work. Thank you so much for this solution 🙌

[Manuel-Kehl]

I was stuck on this going in circles for a while (and actually using questionable workarounds like a sharedForAppIntents Singleton "escape hatch" just so that I can access the objects I'd normally manage through Dependencies from AppIntents 😅)

Really glad I stumbled on this discussion as I can confirm that your proposed workaround to explicitly add the Dependencies prefix in my AppIntents code got it working as expected 🎉
Knowing about the conflicting Dependencies typealias, the compiler error makes a lot more sense to me now but it seemed a little cryptic and unexpected, when I first encountered it...

Since AppIntents are a pretty integral part of modern iOS apps, I'd expect many folks to run into this sooner or later, so I was wondering if it'd maybe make sense to just add short one-liner warning/note about this to the top level README file? Would probably reduce some friction to be aware of this before encountering the problem - even if not immediately applicable, it would be the kind of thing that'd make me go "💡 Ah I remember reading about this in the README when I got started with Dependencies - let me quickly double-check".