Schema: more precise return types when transformations are involved (#4487)

Author: gcanti

.changeset/real-needles-learn.md

@@ -0,0 +1,52 @@
+---
+"effect": patch
+---
+
+Schema: more precise return types when transformations are involved.
+
+- `Chunk`
+- `NonEmptyChunk`
+- `Redacted`
+- `Option`
+- `OptionFromNullOr`
+- `OptionFromUndefinedOr`
+- `OptionFromNullishOr`
+- `Either`
+- `EitherFromUnion`
+- `ReadonlyMap`
+- `Map`
+- `HashMap`
+- `ReadonlySet`
+- `Set`
+- `HashSet`
+- `List`
+- `Cause`
+- `Exit`
+- `SortedSet`
+- `head`
+- `headNonEmpty`
+- `headOrElse`
+
+**Example** (with `Schema.Chunk`)
+
+Before
+
+```ts
+import { Schema } from "effect"
+
+const schema = Schema.Chunk(Schema.Number)
+
+// Property 'from' does not exist on type 'Chunk<typeof Number$>'
+schema.from
+```
+
+After
+
+```ts
+import { Schema } from "effect"
+
+const schema = Schema.Chunk(Schema.Number)
+
+// Schema.Array$<typeof Schema.Number>
+schema.from
+```

packages/effect/dtslint/Schema/Schema.tst.ts

@@ -113,13 +113,12 @@ describe("Cause", () => {
         schema,
         Cause.die(null),
         `(CauseEncoded<string> <-> Cause<string>)
-└─ Encoded side transformation failure
-   └─ CauseEncoded<string>
-      └─ { readonly _tag: "Die"; readonly defect: (string <-> object) }
-         └─ ["defect"]
-            └─ (string <-> object)
-               └─ Type side transformation failure
-                  └─ Expected object, actual null`
+└─ Type side transformation failure
+   └─ Cause<string>
+      └─ CauseEncoded<string>
+         └─ { readonly _tag: "Die"; readonly defect: object }
+            └─ ["defect"]
+               └─ Expected object, actual null`
       )
     })
 

packages/effect/src/Schema.ts

@@ -1,6 +1,5 @@
 import { describe, it } from "@effect/vitest"
-import { Exit } from "effect"
-import * as S from "effect/Schema"
+import { Cause, Exit, Schema as S } from "effect"
 import * as Util from "effect/test/Schema/TestUtils"
 
 describe("Exit", () => {
@@ -42,7 +41,25 @@ describe("Exit", () => {
     )
   })
 
-  it("encoding", async () => {
+  describe("encoding", async () => {
+    it("should raise an error when a non-encodable Cause is passed", async () => {
+      const schema = S.Exit({ failure: S.String, success: S.Number, defect: Util.Defect })
+      await Util.assertions.encoding.fail(
+        schema,
+        Exit.failCause(Cause.die(null)),
+        `(ExitEncoded<number, string, (string <-> object)> <-> Exit<number, string>)
+└─ Type side transformation failure
+   └─ Exit<number, string>
+      └─ Cause<string>
+         └─ CauseEncoded<string>
+            └─ { readonly _tag: "Die"; readonly defect: object }
+               └─ ["defect"]
+                  └─ Expected object, actual null`
+      )
+    })
+  })
+
+  it("using the built-in Defect schema as defect argument", async () => {
     const schema = S.Exit({ failure: S.String, success: S.Number, defect: S.Defect })
     await Util.assertions.encoding.succeed(schema, Exit.fail("error"), {
       _tag: "Failure",