Unions with Zod (like allowing empty string) don't show custom error messages, always Invalid input

Describe the bug

• React Hook Form sends empty fields as '' empty strings.
• Zod can only validate empty strings using unions (see this issue), such as using the or union shorthand: z.string().url().or(z.literal("")), which works correctly.
• The problem arises when using custom error messages: z.string().url('bad URL').or(z.literal("")) always shows the generic Invalid input message.

This basically makes it impossible to use React Hook Forms + Zod + optional fields + custom messages.

To Reproduce Steps to reproduce the behavior:

1. Go to the Sandbox
2. Write abc in the field and submit
3. See Invalid input error instead of the expected bad URL

Codesandbox link https://codesandbox.io/s/lively-smoke-dm61w?file=/src/App.js

Expected behavior The Zod resolver should show the correct custom message.

Desktop (please complete the following information):

• OS: MacOS 11.2.3
• Browser Brave
• Version 1.23.73

Investigation

The structure of errors is deeper when a union is used. See the difference: z.string().url('bad URL').parse('abc')

ZodError: [
  {
    "validation": "url",
    "code": "invalid_string",
    "message": "bad URL",
    "path": []
  }
]

vs union: z.string().url('bad URL').or(z.literal('')).parse('abc')

ZodError: [
  {
    "code": "invalid_union",
    "unionErrors": [
      {
        "issues": [
          {
            "validation": "url",
            "code": "invalid_string",
            "message": "bad URL",
            "path": []
          }
        ]
      },
      {
        "issues": [
          {
            "code": "invalid_type",
            "expected": "",
            "received": "abc",
            "path": [],
            "message": "Expected , received abc"
          }
        ]
      }
    ],
    "path": [],
    "message": "Invalid input"
  }
]

[jorisre]

@verekia fixed in the 2.5.1, let me know if you’ve an issue

[verekia]

Looks solved to me! Thank you very much for the super fast fix.