fix: proper types for more complex cases of array

Fixes #3086

Author: Marsup

lib/index.d.ts

@@ -1705,6 +1705,19 @@ declare namespace Joi {
 
   type ComparatorFunction = (a: any, b: any) => boolean;
 
+  type UnwrapSchemaLikeWithoutArray<T> = T extends SchemaLikeWithoutArray<
+    infer U
+  >
+    ? U
+    : never;
+
+  type NoNestedArrays<T extends readonly unknown[]> = Extract<
+    T[number],
+    readonly unknown[]
+  > extends never
+    ? T
+    : never;
+
   interface ArraySchema<TSchema = any[]> extends AnySchema<TSchema> {
     /**
      * Verifies that an assertion passes for at least one item in the array, where:
@@ -1754,7 +1767,16 @@ declare namespace Joi {
       e: SchemaLikeWithoutArray<E>,
       f: SchemaLikeWithoutArray<F>
     ): ArraySchema<(A | B | C | D | E | F)[]>;
-    items<TItems>(...types: SchemaLikeWithoutArray<TItems>[]): this;
+    items<
+      TItems,
+      TTItems extends SchemaLikeWithoutArray<TItems>[] = SchemaLikeWithoutArray<TItems>[]
+    >(
+      ...types: NoNestedArrays<TTItems>
+    ): ArraySchema<
+      {
+        [I in keyof TTItems]: UnwrapSchemaLikeWithoutArray<TTItems[I]>;
+      }[number][]
+    >;
 
     /**
      * Specifies the exact number of items in the array.

test/index.ts

@@ -401,8 +401,32 @@ expect.error(arrSchema.items([schemaMap, schemaMap, schemaLike]));
 let value1 = Joi.array().items(Joi.string(), Joi.boolean(), Joi.number(), Joi.object({key: Joi.string()}));
 expect.type<Joi.ArraySchema<(string | number | boolean | {key: string})[]>>(value1)
 
-expect.type<Joi.ArraySchema<boolean[]>>(Joi.array().items(Joi.boolean()));
-expect.type<Joi.ArraySchema<number[][]>>(Joi.array().items(Joi.array().items(Joi.number())));
+const arr1 = Joi.array().items(Joi.boolean());
+expect.type<Joi.ArraySchema<boolean[]>>(arr1);
+const arr2 = Joi.array().items<boolean>(Joi.boolean());
+expect.type<Joi.ArraySchema<boolean[]>>(arr2);
+const arr3 = Joi.array().items<number>(Joi.number());
+expect.type<Joi.ArraySchema<number[]>>(arr3);
+const arr4 = Joi.array().items(Joi.array().items(Joi.number()));
+expect.type<Joi.ArraySchema<number[][]>>(arr4);
+const arr5 = Joi.array().items(Joi.number(), Joi.string());
+expect.type<Joi.ArraySchema<(number | string)[]>>(arr5);
+const arr6 = Joi.array().items(Joi.number(), Joi.string(), Joi.boolean());
+expect.type<Joi.ArraySchema<(number | string | boolean)[]>>(arr6);
+const arr7 = Joi.array().items(process.env.NODE_ENV ? Joi.string() : Joi.number());
+expect.type<Joi.ArraySchema<(string | number)[]>>(arr7);
+const arr8 = Joi.array().items(process.env.NODE_ENV ? Joi.string() : Joi.number(), process.env.NODE_ENV ? Joi.boolean() : Joi.date());
+expect.type<Joi.ArraySchema<(string | number | boolean | Date)[]>>(arr8);
+const arr9 = Joi.array().items(
+  Joi.binary(),
+  Joi.boolean(),
+  Joi.date(),
+  Joi.function(),
+  Joi.number(),
+  Joi.object<Record<string,string>>(),
+  Joi.string(),
+);
+expect.type<Joi.ArraySchema<(Buffer | boolean | Date | Function | number | Record<string, string> | string)[]>>(arr9);
 
 // - - - - - - - -