use LazyArg for Effect.if branches (#2451)

Effect-TS · Apr 16, 2024 · 53d1c2a · 53d1c2a
1 parent 9aeae46
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diff --git a/.changeset/three-poems-beg.md b/.changeset/three-poems-beg.md
@@ -0,0 +1,23 @@
+---
+"effect": minor
+---
+
+use LazyArg for Effect.if branches
+
+Instead of:
+
+```ts
+Effect.if(true, {
+  onTrue: Effect.succeed("true"),
+  onFalse: Effect.succeed("false"),
+});
+```
+
+You should now write:
+
+```ts
+Effect.if(true, {
+  onTrue: () => Effect.succeed("true"),
+  onFalse: () => Effect.succeed("false"),
+});
+```
diff --git a/packages/effect/src/Effect.ts b/packages/effect/src/Effect.ts
@@ -3340,16 +3340,12 @@ export const option: <A, E, R>(self: Effect<A, E, R>) => Effect<Option.Option<A>
 
 const if_: {
   <A1, E1, R1, A2, E2, R2>(
-    options: { readonly onTrue: Effect<A1, E1, R1>; readonly onFalse: Effect<A2, E2, R2> }
+    options: { readonly onTrue: LazyArg<Effect<A1, E1, R1>>; readonly onFalse: LazyArg<Effect<A2, E2, R2>> }
   ): <E = never, R = never>(self: boolean | Effect<boolean, E, R>) => Effect<A1 | A2, E1 | E2 | E, R1 | R2 | R>
-  <A1, E1, R1, A2, E2, R2>(
-    self: boolean,
-    options: { readonly onTrue: Effect<A1, E1, R1>; readonly onFalse: Effect<A2, E2, R2> }
-  ): Effect<A1 | A2, E1 | E2, R1 | R2>
-  <E, R, A1, E1, R1, A2, E2, R2>(
-    self: Effect<boolean, E, R>,
-    options: { readonly onTrue: Effect<A1, E1, R1>; readonly onFalse: Effect<A2, E2, R2> }
-  ): Effect<A1 | A2, E | E1 | E2, R | R1 | R2>
+  <A1, E1, R1, A2, E2, R2, E = never, R = never>(
+    self: boolean | Effect<boolean, E, R>,
+    options: { readonly onTrue: LazyArg<Effect<A1, E1, R1>>; readonly onFalse: LazyArg<Effect<A2, E2, R2>> }
+  ): Effect<A1 | A2, E1 | E2 | E, R1 | R2 | R>
 } = core.if_
 
 export {

diff --git a/packages/effect/src/internal/core.ts b/packages/effect/src/internal/core.ts
@@ -926,35 +926,33 @@ export const forEachSequentialDiscard: {
 export const if_ = dual<
   <A1, E1, R1, A2, E2, R2>(
     options: {
-      readonly onTrue: Effect.Effect<A1, E1, R1>
-      readonly onFalse: Effect.Effect<A2, E2, R2>
+      readonly onTrue: LazyArg<Effect.Effect<A1, E1, R1>>
+      readonly onFalse: LazyArg<Effect.Effect<A2, E2, R2>>
     }
   ) => <E = never, R = never>(
     self: Effect.Effect<boolean, E, R> | boolean
   ) => Effect.Effect<A1 | A2, E | E1 | E2, R | R1 | R2>,
-  {
-    <A1, E1, R1, A2, E2, R2>(
-      self: boolean,
-      options: {
-        readonly onTrue: Effect.Effect<A1, E1, R1>
-        readonly onFalse: Effect.Effect<A2, E2, R2>
-      }
-    ): Effect.Effect<A1 | A2, E1 | E2, R1 | R2>
-    <E, R, A1, E1, R1, A2, E2, R2>(
-      self: Effect.Effect<boolean, E, R>,
-      options: {
-        readonly onTrue: Effect.Effect<A1, E1, R1>
-        readonly onFalse: Effect.Effect<A2, E2, R2>
-      }
-    ): Effect.Effect<A1 | A2, E1 | E2 | E, R1 | R2 | R>
-  }
+  <A1, E1, R1, A2, E2, R2, E = never, R = never>(
+    self: Effect.Effect<boolean, E, R> | boolean,
+    options: {
+      readonly onTrue: LazyArg<Effect.Effect<A1, E1, R1>>
+      readonly onFalse: LazyArg<Effect.Effect<A2, E2, R2>>
+    }
+  ) => Effect.Effect<A1 | A2, E1 | E2 | E, R1 | R2 | R>
 >(
   (args) => typeof args[0] === "boolean" || isEffect(args[0]),
-  (self: boolean | Effect.Effect<unknown, unknown, unknown>, { onFalse, onTrue }: {
-    readonly onTrue: Effect.Effect<unknown, unknown, unknown>
-    readonly onFalse: Effect.Effect<unknown, unknown, unknown>
-    // eslint-disable-next-line no-extra-boolean-cast
-  }) => isEffect(self) ? flatMap(self, (b) => (b ? onTrue : onFalse)) : Boolean(self) ? onTrue : onFalse
+  <A1, E1, R1, A2, E2, R2, E = never, R = never>(
+    self: Effect.Effect<boolean, E, R> | boolean,
+    options: {
+      readonly onTrue: LazyArg<Effect.Effect<A1, E1, R1>>
+      readonly onFalse: LazyArg<Effect.Effect<A2, E2, R2>>
+    }
+  ): Effect.Effect<A1 | A2, E1 | E2 | E, R1 | R2 | R> =>
+    isEffect(self)
+      ? flatMap(self, (b): Effect.Effect<A1 | A2, E1 | E2, R1 | R2> => (b ? options.onTrue() : options.onFalse()))
+      : self
+      ? options.onTrue()
+      : options.onFalse()
 )
 
 /* @internal */

diff --git a/packages/effect/src/internal/fiberRuntime.ts b/packages/effect/src/internal/fiberRuntime.ts
@@ -1597,7 +1597,7 @@ export const exists: {
         core.matchEffect(
           forEach(
             elements,
-            (a, i) => core.if_(f(a, i), { onTrue: core.fail(_existsParFound), onFalse: core.unit }),
+            (a, i) => core.if_(f(a, i), { onTrue: () => core.fail(_existsParFound), onFalse: () => core.unit }),
             options
           ),
           {

diff --git a/packages/effect/test/Effect/cause-rendering.test.ts b/packages/effect/test/Effect/cause-rendering.test.ts
@@ -30,8 +30,8 @@ describe("Effect", () => {
       const effect = Effect.withSpan("spanB")(
         Effect.withSpan("spanA")(
           Effect.if(Effect.sync(() => Math.random() > 1), {
-            onTrue: Effect.fail(new E2()),
-            onFalse: Effect.fail(err)
+            onTrue: () => Effect.fail(new E2()),
+            onFalse: () => Effect.fail(err)
           })
         )
       ).pipe(Effect.catchTag("E2", (e) => Effect.die(e)))
@@ -55,8 +55,8 @@ describe("Effect", () => {
       const effect = Effect.withSpan("spanB")(
         Effect.withSpan("spanA")(
           Effect.if(Effect.sync(() => Math.random() > 1), {
-            onTrue: Effect.fail(new E2()),
-            onFalse: Effect.fail(new E1())
+            onTrue: () => Effect.fail(new E2()),
+            onFalse: () => Effect.fail(new E1())
           })
         )
       ).pipe(Effect.catchAll((e) => Effect.fail(e)))
@@ -76,8 +76,8 @@ describe("Effect", () => {
       const effect = Effect.withSpan("spanB")(
         Effect.withSpan("spanA")(
           Effect.if(Effect.sync(() => Math.random() > 1), {
-            onTrue: Effect.fail(new E2()),
-            onFalse: Effect.fail(new E1())
+            onTrue: () => Effect.fail(new E2()),
+            onFalse: () => Effect.fail(new E1())
           })
         )
       ).pipe(Effect.catchTags({ E2: (e) => Effect.die(e) }))

diff --git a/packages/effect/test/Effect/sequencing.test.ts b/packages/effect/test/Effect/sequencing.test.ts
@@ -71,8 +71,8 @@ describe("Effect", () => {
       const result = yield* $(
         true,
         Effect.if({
-          onTrue: Effect.succeed(true),
-          onFalse: Effect.succeed(false)
+          onTrue: () => Effect.succeed(true),
+          onFalse: () => Effect.succeed(false)
         })
       )
       assert.isTrue(result)
@@ -82,8 +82,8 @@ describe("Effect", () => {
       const result = yield* $(
         Effect.succeed(false),
         Effect.if({
-          onFalse: Effect.succeed(true),
-          onTrue: Effect.succeed(false)
+          onFalse: () => Effect.succeed(true),
+          onTrue: () => Effect.succeed(false)
         })
       )
       assert.isTrue(result)