fix(types): correct validation error typing for arrays

fix #351

Author: TheEdoRan

packages/next-safe-action/src/utils.types.ts

@@ -5,3 +5,6 @@ export type Prettify<T> = {
 
 // Returns type or promise of type.
 export type MaybePromise<T> = Promise<T> | T;
+
+// Returns type or array of type.
+export type MaybeArray<T> = T | T[];

packages/next-safe-action/src/validation-errors.types.ts

@@ -1,23 +1,23 @@
 import type { Infer, InferIn, Schema } from "./adapters/types";
-import type { Prettify } from "./utils.types";
+import type { MaybeArray, Prettify } from "./utils.types";
 
 // Basic types and arrays.
 type NotObject = number | string | boolean | bigint | symbol | null | undefined | any[];
 
 // Object with an optional list of validation errors.
-type VEList = Prettify<{ _errors?: string[] }>;
+type VEList<K = undefined> = K extends any[] ? MaybeArray<{ _errors?: string[] }> : { _errors?: string[] };
 
 // Creates nested schema validation errors type using recursion.
 type SchemaErrors<S> = {
-	[K in keyof S]?: S[K] extends NotObject ? VEList : Prettify<VEList & SchemaErrors<S[K]>>;
+	[K in keyof S]?: S[K] extends NotObject ? VEList<S[K]> : Prettify<VEList & SchemaErrors<S[K]>>;
 } & {};
 
 /**
  * Type of the returned object when validation fails.
  */
 export type ValidationErrors<S extends Schema | undefined> = S extends Schema
 	? Infer<S> extends NotObject
-		? VEList
+		? Prettify<VEList>
 		: Prettify<VEList & SchemaErrors<Infer<S>>>
 	: undefined;