Fix error message display for composite errors when `overwrite = fals…

…e` (#3046)

.changeset/breezy-houses-cover.md

@@ -0,0 +1,25 @@
+---
+"@effect/schema": patch
+---
+
+Fix error message display for composite errors when `overwrite = false`
+
+This commit resolves an issue where the custom message for a struct (or tuple or union) was displayed regardless of whether the validation error was related to the entire struct or just a specific part of it. Previously, users would see the custom error message even when the error only concerned a particular field within the struct and the flag `overwrite` was not set to `true`.
+
+```ts
+import { Schema, TreeFormatter } from "@effect/schema"
+import { Either } from "effect"
+
+const schema = Schema.Struct({
+ a: Schema.String
+}).annotations({ message: () => "custom message" })
+
+const res = Schema.decodeUnknownEither(schema)({ a: null })
+if (Either.isLeft(res)) {
+ console.log(TreeFormatter.formatErrorSync(res.left))
+ // before: custom message
+ // now: { readonly a: string }
+ // └─ ["a"]
+ // └─ Expected string, actual null
+}
+```