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packages/foundation/data/validation/src/utils/compose.md

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+# Compose Utilities
+
+## Purpose
+
+The compose utilities provide functional combinators for working with validation results and schemas. `mergeResults` aggregates multiple `ParseResult<T>` values into a single `ParseResult<T[]>`, collecting all issues from failures. `pipe` composes a schema with one or more transform functions into a new pipeline schema, enabling clean left-to-right data transformation chains without manual wrapping.
+
+## Features
+
+- `mergeResults<T>(results)` — aggregate array of results, collecting all failures
+- `pipe<T, U>(schema, ...transforms)` — compose schema with sequential transforms
+
+## Usage: Basic Example
+
+```typescript
+import { pipe, string } from "@suaveplan/validation";
+
+const trimmedLength = pipe(
+  string(),
+  (v: unknown) => (v as string).trim(),
+  (v: unknown) => (v as string).length,
+);
+trimmedLength.parse("  hello  "); // 5
+```
+
+## Usage: Advanced Example
+
+```typescript
+import { mergeResults, number } from "@suaveplan/validation";
+
+const n = number().min(0);
+const results = [1, 2, -3, 4].map((v) => n.safeParse(v));
+const merged = mergeResults(results);
+// merged.success === false, merged.error.issues has one issue for -3
+```
+
+## API Reference
+
+### `mergeResults<T>(results: ParseResult<T>[]): ParseResult<T[]>`
+
+If all results are successes, returns `{ success: true, data: T[] }`.
+If any result is a failure, returns `{ success: false, error: ValidationError }` with all issues aggregated from all failures.
+
+### `pipe<T, U>(schema: BaseSchema<unknown, T>, ...transforms: TransformFn<unknown, unknown>[]): BaseSchema<unknown, U>`
+
+Chains `schema` with each transform in order using `TransformSchema`. Each transform receives the previous stage's output as `unknown` (type-cast by the caller). Returns a new schema producing type `U`.
+
+## Implementation Notes
+
+- `mergeResults` with an empty array returns `{ success: true, data: [] }`.
+- `pipe` with no transforms returns the original schema (zero iterations of the loop).
+- Transform functions in `pipe` accept `unknown` to avoid TypeScript variance issues across the chain; callers must cast appropriately.