Type Incompatibility with Valibot and Transformer Plugins

[Daschi1]

Description

Using the provided configuration example, the client generation completes successfully. However, the generated valibot.gen.ts file contains four TypeScript errors, all caused by the use of v.date() inside a v.pipe(...). These errors prevent successful compilation.

Here’s an example of the problematic generated code:

/**
 * the date of the activities to be found
 */
export const vOrgListActivityFeedsParameterDate = v.pipe(v.string(), v.date());

And here’s one of the TypeScript errors corresponding to the code snippet above when compiling:

src/client/valibot.gen.ts:3603:70 - error TS2769: No overload matches this call.
  Overload 1 of 21, '(schema: StringSchema<undefined>, item1: BaseSchema<string, unknown, BaseIssue<unknown>> | BaseValidation<string, unknown, BaseIssue<unknown>> | BaseTransformation<...> | BaseMetadata<...>): SchemaWithPipe<...>', gave the following error.
    Argument of type 'DateSchema<undefined>' is not assignable to parameter of type 'BaseSchema<string, unknown, BaseIssue<unknown>>'.
      Types of property '~standard' are incompatible.
        Type 'StandardProps<Date, Date>' is not assignable to type 'StandardProps<string, unknown>'.
          Type 'Date' is not assignable to type 'string'.

  Overload 2 of 21, '(schema: StringSchema<undefined>, ...items: readonly PipeItem<string, string, BaseIssue<unknown>>[]): SchemaWithPipe<readonly [StringSchema<undefined>, ...PipeItem<string, string, BaseIssue<...>>[]]>', gave the following error.
    Argument of type 'DateSchema<undefined>' is not assignable to parameter of type 'PipeItem<string, string, BaseIssue<unknown>>'.
      Type 'DateSchema<undefined>' is not assignable to type 'BaseSchema<string, string, BaseIssue<unknown>>'.
        Types of property '~standard' are incompatible.
          Type 'StandardProps<Date, Date>' is not assignable to type 'StandardProps<string, string>'.
            Type 'Date' is not assignable to type 'string'.

This same error occurs at four locations throughout the generated file.

I haven’t fully investigated the root cause, but from some quick testing, it looks like the issue is related to the combination of the valibot and @hey-api/transformers plugins (with dates: true). The generated validator is trying to transform a string to a Date using v.date(), which appears to conflict with Valibot’s type expectations in this context.

As an experiment, I tried replacing v.date() with v.isoDateTime(), like so:

v.pipe(v.string(), v.isoDateTime())

With that change, the TypeScript errors go away. So perhaps the issue is that v.date() expects an actual Date object as input, while v.isoDateTime() validates string input and may be more appropriate here.

---

Reproducible example or configuration

import { createClient, UserConfig } from "@hey-api/openapi-ts";

const userConfig: UserConfig = {
  input: "https://code.forgejo.org/swagger.v1.json",
  output: "src/client",
  plugins: [
    {
      name: "@hey-api/client-fetch",
      bundle: true,
      baseUrl: "https://code.forgejo.org",
    },
    {
      name: "@hey-api/typescript",
      enums: "javascript",
    },
    {
      name: "@hey-api/sdk",
      validator: true,
      transformer: true,
    },
    {
      name: "valibot",
    },
    {
      name: "@hey-api/transformers",
      dates: true,
    },
  ],
  logs: {
    file: false,
    level: "debug",
  },
  dryRun: false,
};

createClient(userConfig)
  .then(() => console.log("Client generation completed successfully"))
  .catch((error) => console.error("Failed to generate client:", error));

---

OpenAPI specification (optional)

https://code.forgejo.org/swagger.v1.json

---

System information (optional)

Dependencies

• @hey-api/client-fetch version 0.11.0
• @hey-api/openapi-ts version 0.69.0
• valibot version 1.1.0

Environment

• OS: Windows 11
• Node.js: v22.16.0
• TypeScript: 5.8.3

[mrlubos]

This will be fixed in the next release 🙌

[Daschi1]

Awesome, thanks! Any rough ETA on when the next release might be published? 👀

[mrlubos]

I'll do it probably end of my day today

[Daschi1]

@mrlubos sorry for pinging you, but I just realized through testing that v.isoDateTime() was the wrong helper to use. It only validates the yyyy-MM-ddThh:mm format (no seconds or offset) per the docs (https://valibot.dev/api/isoDateTime/), whereas OpenAPI's format: "date-time" explicitly allows full RFC 3339 timestamps (seconds + offset) (see https://swagger.io/specification/v2/#data-types).

The correct Valibot action is v.isoTimestamp() (https://valibot.dev/api/isoTimestamp/). Apologies for suggesting the wrong one earlier, I should have read the Valibot docs more carefully. I only just noticed once I actually ran the generated client against an API endpoint returning date-times.

I tested this on /user/repos by manually replacing all v.isoDateTime calls with v.isoTimestamp, and it removes the validation errors I was getting:

{
      kind: 'validation',
      type: 'iso_date_time',
      input: '1970-01-01T01:00:00+01:00',
      expected: null,
      received: '"1970-01-01T01:00:00+01:00"',
      message: 'Invalid date-time: Received "1970-01-01T01:00:00+01:00"',
      requirement: /^\d{4}-(?:0[1-9]|1[0-2])-(?:[12]\d|0[1-9]|3[01])[T ](?:0\d|1\d|2[0-3]):[0-5]\d$/u,
      path: [Array],
      issues: undefined,
      lang: undefined,
      abortEarly: undefined,
      abortPipeEarly: undefined
}

With v.isoTimestamp(), that error goes away and the response parses correctly.

(If you want me to open a separate issue instead, I can do that as well.)

[mrlubos]

@Daschi1 Yes please or I'll lose track of it. If you want to open a pull request, even better 🤝

[Daschi1]

@mrlubos Done! Please find the issue here: #2191 and the PR here: #2192.
Let me know over there if any changes are needed!