bug(zod): `zx.toType` doesn't handle `z.templateLiteral` with `z.enum`, `z.nullable`, `z.optional`

[gnlow]

Minimal Reproduction

import { z } from "https://esm.sh/zod@4.1.9"
import { zx } from "https://esm.sh/@traversable/zod@0.0.48"

console.log(
    zx.toType(z.templateLiteral([
        "Hello, ",
        z.union([z.string(), z.number()]),
    ]))
)

console.log(
    zx.toType(z.templateLiteral([
        z.enum(["a", "b"]),
        z.literal(["c", "d"]),
    ]))
)

console.log(
    zx.toType(z.templateLiteral([
        z.number().nullable(),
        "px",
    ]))
)

console.log(
    zx.toType(z.templateLiteral([
        z.number().optional(),
        "px",
    ]))
)

Expected

`Hello, ${string}` | `Hello, ${number}`
"ac" | "ad" | "bc" | "bd"
`${number}px` | "nullpx"
"px" | `${number}px`

Actual

"Hello, [object Object]"
"[object Object]c" | "[object Object]d"
"[object Object]px"
"[object Object]px"

note

• I'm not sure whether the last one should be "px" | `${number}px` or `${number}px` | "undefinedpx".
  • The z.templateLiteral has z.ZodTemplateLiteral<"px" | `${number}px` type.
  • type A = `${number | undefined}` seems to be handled as type A = `${number}` | "undefined" in TypeScript.
  • Maybe it's intended behavior of Zod (Add z.literal.template() colinhacks/zod#1786).

[ahrjarrett]

@gnlow thanks for discovering this.

I did not realize z.templateLiteral supported optional and nullable schemas 🤔 I don't think adding that should be too difficult.

The nested unions might be difficult, since if unions are supported, then nested unions are supported.

I'll work on this as soon as I can, but the fix for the unions part I'm going to have to think about – so I might break this into 2 tickets if that's alright with you.

[gnlow]

@ahrjarrett That works for me 👍

[ahrjarrett]

zx.toType now handles z.nullable, z.optional and z.enum types inside z.templateLiteral correctly.

The fix is available in @traversable/zod@0.0.52.

@gnlow see #531 to track progress on handling z.union types.

Thanks for reporting this! Now to figure out how to recursively distribute unions while preserving position inside strings 😵