feat: add isZodTypeLike

Author: joshunrau

src/__tests__/zod4.test.ts

@@ -1,6 +1,8 @@
-import { expectTypeOf, test } from 'vitest';
-import type { z as z3 } from 'zod/v3';
-import type { z as z4 } from 'zod/v4';
+import { describe, expect, expectTypeOf, it, test } from 'vitest';
+import { z as z3 } from 'zod/v3';
+import { z as z4 } from 'zod/v4';
+
+import { isZodTypeLike } from '../zod4.js';
 
 import type {
   ZodErrorLike,
@@ -48,3 +50,22 @@ test('ZodTypeLike', () => {
   expectTypeOf<z4.ZodNumber>().toMatchTypeOf<ZodTypeLike<number>>();
   expectTypeOf<z4.ZodNumber>().not.toMatchTypeOf<ZodTypeLike<string>>();
 });
+
+describe('isZodTypeLike', () => {
+  it('should return true for Zod v3 types', () => {
+    expect(isZodTypeLike(z3.object({}))).toBe(true);
+    expect(isZodTypeLike(z3.number())).toBe(true);
+    expect(isZodTypeLike(z3.any())).toBe(true);
+  });
+  it('should return true for Zod v4 types', () => {
+    expect(isZodTypeLike(z4.object({}))).toBe(true);
+    expect(isZodTypeLike(z4.number())).toBe(true);
+    expect(isZodTypeLike(z4.any())).toBe(true);
+  });
+  it('should return false for an object without a standard schema', () => {
+    expect(isZodTypeLike({})).toBe(false);
+  });
+  it('should return false for an object with a standard schema, but the incorrect vendor name', () => {
+    expect(isZodTypeLike({ '~standard': { vendor: 'DNP' } })).toBe(false);
+  });
+});

src/zod4.ts

@@ -1,3 +1,5 @@
+import { isObjectLike, isPlainObject } from './object.js';
+
 export type ZodIssueLike = {
   [key: string]: any;
   readonly code: string;
@@ -29,4 +31,16 @@ export type ZodTypeLike<TOutput, TInput = unknown> = {
   readonly _input: TInput;
   readonly _output: TOutput;
   safeParseAsync: (data: unknown) => Promise<ZodSafeParseResultLike<TOutput>>;
+  '~standard': {
+    [key: string]: any;
+    vendor: string;
+  };
 };
+
+export function isZodTypeLike(arg: unknown): arg is ZodTypeLike<unknown> {
+  if (!isObjectLike(arg)) {
+    return false;
+  }
+  const standardSchema: unknown = Reflect.get(arg, '~standard');
+  return isPlainObject(standardSchema) && standardSchema.vendor === 'zod';
+}