Expose Random Tag and functions to use a specific random service implementation (#2137)

Author: mikearnaldi

.changeset/four-toes-double.md

@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+Expose Random Tag and functions to use a specific random service implementation

packages/effect/src/Effect.ts

@@ -4524,6 +4524,28 @@ export const random: Effect<Random.Random> = effect.random
 export const randomWith: <A, E, R>(f: (random: Random.Random) => Effect<A, E, R>) => Effect<A, E, R> =
   defaultServices.randomWith
 
+/**
+ * Executes the specified workflow with the specified implementation of the
+ * random service.
+ *
+ * @since 2.0.0
+ * @category random
+ */
+export const withRandom: {
+  <A extends Random.Random>(value: A): <A, E, R>(effect: Effect<A, E, R>) => Effect<A, E, R>
+  <A extends Random.Random, E, R>(effect: Effect<A, E, R>, value: A): Effect<A, E, R>
+} = defaultServices.withRandom
+
+/**
+ * Sets the implementation of the random service to the specified value and
+ * restores it to its original value when the scope is closed.
+ *
+ * @since 2.0.0
+ * @category constructors
+ */
+export const withRandomScoped: <A extends Random.Random>(value: A) => Effect<void, never, Scope.Scope> =
+  fiberRuntime.withRandomScoped
+
 // -------------------------------------------------------------------------------------
 // runtime
 // -------------------------------------------------------------------------------------

packages/effect/src/Random.ts

@@ -2,6 +2,7 @@
  * @since 2.0.0
  */
 import type * as Chunk from "./Chunk.js"
+import type * as Context from "./Context.js"
 import type * as Effect from "./Effect.js"
 import * as defaultServices from "./internal/defaultServices.js"
 import * as internal from "./internal/random.js"
@@ -111,3 +112,9 @@ export const shuffle: <A>(elements: Iterable<A>) => Effect.Effect<Chunk.Chunk<A>
  */
 export const randomWith: <A, E, R>(f: (random: Random) => Effect.Effect<A, E, R>) => Effect.Effect<A, E, R> =
   defaultServices.randomWith
+
+/**
+ * @since 2.0.0
+ * @category context
+ */
+export const Random: Context.Tag<Random, Random> = internal.randomTag

packages/effect/src/internal/defaultServices.ts

@@ -102,6 +102,16 @@ export const randomWith = <A, E, R>(f: (random: Random.Random) => Effect.Effect<
     (services) => f(Context.get(services, random.randomTag))
   )
 
+/** @internal */
+export const withRandom = dual<
+  <A extends Random.Random>(value: A) => <A, E, R>(effect: Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>,
+  <A extends Random.Random, E, R>(effect: Effect.Effect<A, E, R>, value: A) => Effect.Effect<A, E, R>
+>(2, (effect, value) =>
+  core.fiberRefLocallyWith(
+    currentServices,
+    Context.add(random.randomTag, value)
+  )(effect))
+
 /** @internal */
 export const next: Effect.Effect<number> = randomWith((random) => random.next)
 

packages/effect/src/internal/fiberRuntime.ts

@@ -28,6 +28,7 @@ import * as MRef from "../MutableRef.js"
 import * as Option from "../Option.js"
 import { pipeArguments } from "../Pipeable.js"
 import * as Predicate from "../Predicate.js"
+import type * as Random from "../Random.js"
 import * as RA from "../ReadonlyArray.js"
 import * as Ref from "../Ref.js"
 import type { Entry, Request } from "../Request.js"
@@ -59,6 +60,7 @@ import * as metric from "./metric.js"
 import * as metricBoundaries from "./metric/boundaries.js"
 import * as metricLabel from "./metric/label.js"
 import * as OpCodes from "./opCodes/effect.js"
+import { randomTag } from "./random.js"
 import { complete } from "./request.js"
 import * as _runtimeFlags from "./runtimeFlags.js"
 import { OpSupervision } from "./runtimeFlags.js"
@@ -2705,6 +2707,10 @@ export const validateFirst = dual<
 export const withClockScoped = <A extends Clock.Clock>(value: A) =>
   fiberRefLocallyScopedWith(defaultServices.currentServices, Context.add(clock.clockTag, value))
 
+/* @internal */
+export const withRandomScoped = <A extends Random.Random>(value: A) =>
+  fiberRefLocallyScopedWith(defaultServices.currentServices, Context.add(randomTag, value))
+
 /* @internal */
 export const withConfigProviderScoped = (value: ConfigProvider) =>
   fiberRefLocallyScopedWith(defaultServices.currentServices, Context.add(configProviderTag, value))