Uncaught TypeError: Cannot convert a Symbol value to a number

The following code sample will throw said error because after the validation failed the refine function is still called:

z.union([z.number(), z.string().transform(z.number(), Number.parseFloat)])
  .refine((v) => v >= 1)
  .parse("foo");

This is supposed to accept 5 or "5" and reject anything that is not parsable into a positive number.

But the refine will be called even if the union parsing failed and then v will be Symbol("invalid_data")

> z.union([z.number(), z.string().transform(z.number(), Number.parseFloat)]).refine((v) => v >= 1).parse("foo");
Uncaught TypeError: Cannot convert a Symbol value to a number
    at repl:1:92
    at Object.check (/home/despairblue/git/wunderflats/api/node_modules/zod/lib/cjs/types/base.js:167:34)
    at ZodUnion.parse (/home/despairblue/git/wunderflats/api/node_modules/zod/lib/cjs/parser.js:892:41)
> 

Without the refine it works as expected:

> z.union([z.number(), z.string().transform(z.number(), Number.parseFloat)]).parse("foo");
Uncaught ZodError: [
  {
    "code": "invalid_union",
    "unionErrors": [
      {
        "issues": [
          {
            "code": "invalid_type",
            "expected": "number",
            "received": "string",
            "path": [],
            "message": "Expected number, received string"
          }
        ]
      },
      {
        "issues": [
          {
            "code": "invalid_type",
            "expected": "number",
            "received": "nan",
            "path": [],
            "message": "Expected number, received nan"
          }
        ]
      }
    ],
    "path": [],
    "message": "Invalid input"
  }
]
    at new ZodError (/home/despairblue/git/wunderflats/api/node_modules/zod/lib/cjs/ZodError.js:73:28)
    at ZodUnion.parse (/home/despairblue/git/wunderflats/api/node_modules/zod/lib/cjs/parser.js:195:17) {
  issues: [
    {
      code: 'invalid_union',
      unionErrors: [Array],
      path: [],
      message: 'Invalid input'
    }
  ],
  addIssue: [Function],
  addIssues: [Function],
  flatten: [Function]
}
> 

Question regarding this. It seem refine function are not allowed to throw. Does that mean a refine function must succeed?

Forget the last part as they can return false obviously.

[colinhacks]

Thanks for all your work on this! I merged these last night 🤙

[despairblue]

I created 2 PRs, one for the bug and one for making it clear that refinements and transformers must not throw.

don’t think the “trick” you’re referring to should be documented as a valid/acceptable approach. Like you say elsewhere, you should use refinements to make sure the inputs are valid before calling .transform

Makes sense, but I’ll probably just continue using it like this. The reason is that needing a refinement and a transformer to be kept in sync (which may also be defined in totally different places) is a bug that is just waiting to happen. Technically it’s a clean separation of concerns, but the usability for the developer/team using this is hurt by this I fear.

Regarding 3. I currently went with defining all refinements and transformations in another file and wrap them in a try catch function, the refinement one returns just false on error and the transformer the value that was passed in. Seems to work so far.