Define animations statically but resolve them at runtime

AnimationClient.swift

import Dependencies
import Foundation
import SwiftUI

/// The things you could vary the animation on.
struct AnimationResolutionInput {
    // This makes no sense, it's an example!
    var colorScheme: ColorScheme
}

/// A way to create an animation based on some inputs.
protocol AnimationResolvable {
    func resolve(input: AnimationResolutionInput) -> Animation?
}

/// The client
struct AnimationClient: Sendable {
    /// self.animationClient.resolve(.sample)
    var resolve: @Sendable (any AnimationResolvable) -> Animation?
}
extension AnimationClient: DependencyKey {
    static let testValue = Self(
        resolve: unimplemented("\(Self.self).resolve", placeholder: nil)
    )
    static let liveValue = Self(
        // Gather the data to perform resolution using other @Dependency or whatever.
        resolve: { $0.resolve(input: .init(colorScheme: .dark)) }
    )
}
extension DependencyValues {
    var animationClient: AnimationClient {
        get { self[AnimationClient.self] }
        set { self[AnimationClient.self] = newValue }
    }
}

/// A sample animation.
struct SampleAnimation: AnimationResolvable {
    func resolve(input: AnimationResolutionInput) -> Animation? {
        .default
    }
}
extension AnimationResolvable where Self == SampleAnimation {
    // Note you can choose to make this public or not, letting you
    // decie whether other modules can use this animation.
    static var sample: Self { SampleAnimation() }
}