feat: add z.ext namespace for safe plugin extension

[Ayush2k02]

Fixes #5544

Adds a mutable z.ext namespace to allow community plugins to extend Zod without modifying the frozen core z object. This addresses the issue where direct property assignment fails in production builds.

Example of failing code:

// Works in dev, breaks in prod
z.iso.timezone = () => z.string().check(...);
// TypeError: Cannot assign to read only property

Solution

Implemented z.ext as a dedicated, mutable namespace specifically for plugins. This approach:

• ✅ Maintains discoverability through z.ext.* with IDE autocomplete
• ✅ Avoids any breaking changes to the core z object

Usage Example

Plugin Author:

import { z } from 'zod';

// Register plugin on z.ext
z.ext.cron = () => {
  return z.string().refine(
    (val) => /^(\*|([0-5]?\d)) (\*|([01]?\d|2[0-3]))/.test(val),
    { message: "Invalid cron expression" }
  );
};

// TypeScript support via declaration merging
declare module 'zod' {
  namespace z {
    namespace ext {
      function cron(): ZodString;
    }
  }
}

Consumer:

import 'my-zod-cron-plugin'; // Side-effect import
import { z } from 'zod';

const cronSchema = z.ext.cron();
cronSchema.parse("0 0"); // ✅ Valid
cronSchema.parse("invalid"); // ❌ Throws error

Test Results

• ✅ Basic plugin extension
• ✅ Multiple plugins coexisting
• ✅ Core z object remains unaffected

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[Ayush2k02]

Hey, any updates on this !