Add Service.layer() constructor for type-safe layer creation

.changeset/service-deps-layer-typing.md

@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+Fix Service helper typing so dependency layers eliminate make requirements, add docgen @since for Service exports, and cover dependency elimination with dtslint checks.

packages/effect/dtslint/Service.tst.ts

@@ -0,0 +1,35 @@
+import type { Layer } from "effect"
+import { Effect, Service } from "effect"
+import { describe, expect, it } from "tstyche"
+
+describe("Service public typing", () => {
+  it("layer removes requirements satisfied by dependencies", () => {
+    class Config extends Service<Config>()("Config", {
+      make: (prefix: string) => Effect.succeed({ prefix })
+    }) {}
+
+    class Logger extends Service<Logger>()("Logger", {
+      make: Effect.gen(function*() {
+        const cfg = yield* Config
+        return { log: (msg: string) => Effect.succeed(`${cfg.prefix}:${msg}`) }
+      }),
+      dependencies: [Config.layer("cfg")]
+    }) {}
+
+    expect(Logger.layer).type.toBe<Layer.Layer<Logger>>()
+    expect(Logger.layerWithoutDependencies).type.toBe<Layer.Layer<Logger, never, Config>>()
+  })
+
+  it("factory make keeps constructor parameters on layer", () => {
+    class Http extends Service<Http>()("Http", {
+      make: (base: string, timeout: number) =>
+        Effect.succeed({
+          base,
+          timeout,
+          get: (path: string) => Effect.succeed(`${base}${path}`)
+        })
+    }) {}
+
+    expect(Http.layer).type.toBe<(base: string, timeout: number) => Layer.Layer<Http, never, never>>()
+  })
+})

packages/effect/src/Service.ts

@@ -0,0 +1,298 @@
+import type * as EffectTypes from "./Effect.ts"
+import * as Effect from "./Effect.ts"
+import { isEffect } from "./internal/core.ts"
+import * as Layer from "./Layer.ts"
+import type { Scope } from "./Scope.ts"
+import * as ServiceMap from "./ServiceMap.ts"
+import type * as Types from "./types/Types.ts"
+
+/**
+ * Extracts the Effect type from a make function or Effect value.
+ *
+ * @since 4.0.0
+ * @category Internal
+ */
+type MakeEffect<Make> = Make extends (...args: Array<any>) => EffectTypes.Effect<any, any, any> ? ReturnType<Make>
+  : Make
+
+/**
+ * Extracts the argument types from a make function.
+ *
+ * @since 4.0.0
+ * @category Internal
+ */
+type MakeArgs<Make> = Make extends (...args: infer Args) => EffectTypes.Effect<any, any, any> ? Args : never
+
+/**
+ * Extracts the combined service requirements from dependency layers.
+ *
+ * @since 4.0.0
+ * @category Internal
+ */
+type DepsContext<Deps extends ReadonlyArray<Layer.Layer<any, any, any>> | undefined> = Deps extends
+  ReadonlyArray<Layer.Layer<any, any, any>> ? Layer.Services<Deps[number]>
+  : never
+
+/**
+ * Lifts a value, Promise, or Effect into an Effect type.
+ *
+ * @since 4.0.0
+ * @category Internal
+ */
+type LiftToEffect<X> = X extends EffectTypes.Effect<infer A, infer E, infer R> ? EffectTypes.Effect<A, E, R>
+  : X extends Promise<infer A> ? EffectTypes.Effect<A, unknown>
+  : EffectTypes.Effect<X, never>
+
+/**
+ * Layer type without dependencies - requires what make effect requires (excluding Scope).
+ *
+ * @since 4.0.0
+ * @category Internal
+ */
+type LayerShapeNoDeps<Self, Eff> = Layer.Layer<
+  Self,
+  EffectTypes.Error<Eff>,
+  Exclude<EffectTypes.Services<Eff>, Scope>
+>
+
+/**
+ * Layer type with dependencies - requires only what dependency layers require.
+ *
+ * @since 4.0.0
+ * @category Internal
+ */
+type LayerShapeWithDeps<Self, Eff, DepsReq> = Layer.Layer<Self, EffectTypes.Error<Eff>, DepsReq>
+
+/**
+ * Converts an optional dependency array to a non-empty tuple type.
+ *
+ * @since 4.0.0
+ * @category Internal
+ */
+type NonEmptyDeps<Deps extends ReadonlyArray<Layer.Layer<any, any, any>> | undefined> = Deps extends
+  ReadonlyArray<infer L> ? readonly [L, ...Array<L>] : never
+
+/**
+ * Generates the layer type from make function, handling both factory and value cases.
+ *
+ * @since 4.0.0
+ * @category Internal
+ */
+type LayerFromMake<Self, Make, Deps extends ReadonlyArray<Layer.Layer<any, any, any>> | undefined> = Deps extends
+  undefined ? ([MakeArgs<Make>] extends [never] ? LayerShapeNoDeps<Self, MakeEffect<Make>>
+      : (...args: MakeArgs<Make>) => LayerShapeNoDeps<Self, MakeEffect<Make>>)
+  : ([MakeArgs<Make>] extends [never] ? LayerShapeWithDeps<Self, MakeEffect<Make>, DepsContext<Deps>>
+    : (...args: MakeArgs<Make>) => LayerShapeWithDeps<Self, MakeEffect<Make>, DepsContext<Deps>>)
+
+/**
+ * Layer type ignoring dependencies - always requires what make effect requires.
+ *
+ * @since 4.0.0
+ * @category Internal
+ */
+type LayerWithoutDepsFromMake<Self, Make> = [MakeArgs<Make>] extends [never] ? LayerShapeNoDeps<Self, MakeEffect<Make>>
+  : (...args: MakeArgs<Make>) => LayerShapeNoDeps<Self, MakeEffect<Make>>
+
+// Type guard to check if a value is a Promise.
+const isPromise = (u: unknown): u is Promise<unknown> =>
+  typeof u === "object" && u !== null && "then" in u && typeof (u as any).then === "function"
+
+// Builds the `use` helper for a service, allowing callback-based access.
+const buildUse = (service: any) => {
+  return <X>(f: (svc: any) => X): EffectTypes.Effect<any, any, any> =>
+    Effect.gen(function*() {
+      const svc = yield* service
+      const result = f(svc)
+      if (isEffect(result)) {
+        return yield* result
+      }
+      if (isPromise(result)) {
+        return yield* Effect.promise(() => result)
+      }
+      return result
+    })
+}
+
+// Builds the `layer` or `layerWithoutDependencies`, handling factories and dependency provision.
+const buildLayer = (
+  service: any,
+  make: EffectTypes.Effect<any, any, any> | ((...args: Array<any>) => EffectTypes.Effect<any, any, any>),
+  dependencies?: ReadonlyArray<Layer.Layer<any, any, any>>
+) => {
+  const isFactory = typeof make === "function"
+  const depsLayer = dependencies && dependencies.length > 0
+    ? Layer.mergeAll(...(dependencies as NonEmptyDeps<typeof dependencies>))
+    : undefined
+
+  const base = (...args: Array<any>) => {
+    const eff = isFactory ? (make as any)(...args) : make
+    return Layer.effect(service, eff)
+  }
+
+  return depsLayer
+    ? isFactory
+      ? (...args: Array<any>) => Layer.provide(base(...args), depsLayer)
+      : Layer.provide(base(), depsLayer)
+    : isFactory
+    ? (...args: Array<any>) => base(...args)
+    : base()
+}
+
+/**
+ * Extended ServiceClass with layer helpers for services with `make`.
+ *
+ * Provides:
+ * - `make`: The effect or factory function to create the service
+ * - `use`: Callback-based service access
+ * - `layer`: Layer constructor respecting dependencies
+ * - `layerWithoutDependencies`: Layer constructor ignoring dependencies (only when deps provided)
+ *
+ * @since 4.0.0
+ * @category Models
+ */
+export type ServiceWithMake<
+  Self,
+  Id extends string,
+  Shape,
+  Make extends EffectTypes.Effect<any, any, any> | ((...args: any) => EffectTypes.Effect<any, any, any>),
+  Deps extends ReadonlyArray<Layer.Layer<any, any, any>> | undefined
+> = ServiceMap.ServiceClass<Self, Id, Shape> & {
+  readonly make: Make
+  readonly use: <X>(f: (svc: Shape) => X) => LiftToEffect<X>
+  readonly layer: LayerFromMake<Self, Make, Deps>
+  readonly layerWithoutDependencies: Deps extends undefined ? never : LayerWithoutDepsFromMake<Self, Make>
+}
+
+/**
+ * Creates a service with layer helpers when `make` is provided.
+ *
+ * @example
+ * ```ts
+ * import { Service, Effect } from "effect"
+ *
+ * class Logger extends Service<Logger>()("Logger", {
+ *   make: Effect.sync(() => ({ log: (msg: string) => console.log(msg) }))
+ * }) {}
+ *
+ * // Use Logger.layer, Logger.use, etc.
+ * ```
+ *
+ * @since 4.0.0
+ * @category Constructors
+ */
+export type ServiceConstructor = {
+  // Plain tag (no make)
+  <Identifier, Shape = Identifier>(key: string): ServiceMap.Service<Identifier, Shape>
+  // Curried with explicit Shape; make optional
+  <Self, Shape>(): <
+    const Identifier extends string,
+    E,
+    R = Types.unassigned,
+    Args extends ReadonlyArray<any> = never,
+    Deps extends ReadonlyArray<Layer.Layer<any, any, any>> | undefined = undefined
+  >(
+    id: Identifier,
+    options?: {
+      readonly make?: ((...args: Args) => EffectTypes.Effect<Shape, E, R>) | EffectTypes.Effect<Shape, E, R> | undefined
+      readonly dependencies?: Deps
+    } | undefined
+  ) => [Types.unassigned] extends [R] ? ServiceMap.ServiceClass<Self, Identifier, Shape>
+    : ServiceWithMake<
+      Self,
+      Identifier,
+      Shape,
+      [Args] extends [never] ? EffectTypes.Effect<Shape, E, R> : (...args: Args) => EffectTypes.Effect<Shape, E, R>,
+      Deps
+    >
+  // Curried with inferred Shape; make required
+  <Self>(): <
+    const Identifier extends string,
+    Make extends EffectTypes.Effect<any, any, any> | ((...args: any) => EffectTypes.Effect<any, any, any>),
+    Deps extends ReadonlyArray<Layer.Layer<any, any, any>> | undefined = undefined
+  >(
+    id: Identifier,
+    options: {
+      readonly make: Make
+      readonly dependencies?: Deps
+    }
+  ) => ServiceWithMake<
+    Self,
+    Identifier,
+    Make extends
+      | EffectTypes.Effect<infer _A, infer _E, infer _R>
+      | ((...args: infer _Args) => EffectTypes.Effect<infer _A, infer _E, infer _R>) ? _A
+      : never,
+    Make,
+    Deps
+  >
+}
+
+const ServiceImpl = (...args: Array<any>) => {
+  if (args.length === 0) {
+    const baseService = ServiceMap.Service()
+
+    return function(key: string, options?: {
+      readonly make?: any
+      readonly dependencies?: ReadonlyArray<Layer.Layer<any, any, any>>
+    }) {
+      const service = options?.make
+        ? baseService(key, { make: options.make })
+        : baseService(key)
+
+      if (options?.make) {
+        const deps = options.dependencies
+        type Self = typeof service
+        type Make = typeof options.make
+        type Deps = typeof deps
+
+        const svc = service as Types.Mutable<
+          & ServiceMap.ServiceClass<Self, typeof service.key, typeof service.Service>
+          & Partial<ServiceWithMake<Self, typeof service.key, typeof service.Service, Make, Deps>>
+        >
+
+        svc.layer = buildLayer(svc, options.make, deps) as LayerFromMake<Self, Make, Deps>
+        if (deps && deps.length > 0) {
+          svc.layerWithoutDependencies = buildLayer(svc, options.make) as LayerWithoutDepsFromMake<Self, Make>
+        }
+        svc.use = buildUse(svc) as ServiceWithMake<Self, typeof service.key, typeof service.Service, Make, Deps>["use"]
+      }
+
+      return service
+    }
+  }
+
+  return (ServiceMap.Service as (...fnArgs: Array<any>) => any)(...args)
+}
+
+/**
+ * Layer-aware service constructor. Use this when providing `make` to get
+ * automatic `layer`, `layerWithoutDependencies`, and `use` helpers.
+ *
+ * @example
+ * ```ts
+ * import { Service, Effect } from "effect"
+ *
+ * class Logger extends Service<Logger>()("Logger", {
+ *   make: Effect.sync(() => ({ log: (msg: string) => console.log(msg) }))
+ * }) {}
+ *
+ * // Use Logger.layer, Logger.use, etc.
+ * ```
+ *
+ * @since 4.0.0
+ */
+export const Service = ServiceImpl as ServiceConstructor
+
+/**
+ * Alias to the underlying service tag type.
+ *
+ * @since 4.0.0
+ */
+export type ServiceTag<Identifier, Shape = Identifier> = ServiceMap.Service<Identifier, Shape>
+
+/**
+ * Alias to the underlying service class type.
+ *
+ * @since 4.0.0
+ */
+export type ServiceClass<Self, Identifier extends string, Shape> = ServiceMap.ServiceClass<Self, Identifier, Shape>

packages/effect/src/index.ts

@@ -1298,6 +1298,17 @@ export * as ScopedRef from "./ScopedRef.ts"
  *
  * @since 4.0.0
  */
+export {
+  /**
+   * Layer-aware service constructor with automatic helpers.
+   *
+   * @since 4.0.0
+   */
+  Service
+} from "./Service.ts"
+/**
+ * @since 4.0.0
+ */
 export * as ServiceMap from "./ServiceMap.ts"
 
 /**