@open-form-spec/plugin-yup

Generates type-preserving yup validation schemas from Open Form Spec files.

The generated code handles Layer 1 — field states (required / optional / forbidden), conditional logic (.when()), and enum constraints (.oneOf()). You only override fields where you need additional content validation.

Setup

// ofs.config.js
import { defineConfig } from "@open-form-spec/plugin";
import { yupGenerator } from "@open-form-spec/plugin-yup";

export default defineConfig({
  specs: "src/specs/**/*.ofs.yaml",
  openapi: { api: "src/openapi.yaml" },
  plugins: [
    yupGenerator({
      output: "src/generated/ofs",
      enumImport: "@/api/generated/backend/index.schemas",
    }),
  ],
});

npx ofs generate

What Gets Generated

For each spec section, the plugin generates a defaults object, a Fields type, and a schema function:

// registration.ofs.ts (auto-generated)
import { AccountType } from "@/api/generated/backend/index.schemas";

export const registrationDefaults = {
  email: yup.string(),
  accountType: yup.string().oneOf(Object.values(AccountType)),
  nickname: yup.string(),
};
export type RegistrationFields = typeof registrationDefaults;

export function registrationSchema<T extends Partial<RegistrationFields>>(overrides?: T) {
  const fields = { ...registrationDefaults, ...overrides };

  return yup.object().shape({
    email: fields.email.required(),
    accountType: fields.accountType.required(),
    nickname: fields.nickname.optional(),
  });
}

Types are fully preserved — RegistrationFields["accountType"] is StringSchema<"PERSONAL" | "BUSINESS" | ... | undefined>, not just StringSchema<string>.

Usage

Override only the fields where you need additional validation:

import { registrationSchema } from "./generated/ofs/registration.ofs";

const schema = registrationSchema({
  email: yup.string().email("Invalid email"),
  password: yup.string().min(8),
});

Fields you don't override keep their generated defaults — correct type, enum .oneOf(), format-specific factory. Layer 2 overrides should not call .required() or .optional() — Layer 1 handles that.

Plugin Options

| Option | Type | Description | |--------|------|-------------| | output | string | Output directory, relative to config root | | enumImport | string | Import path for enum types. Enables .oneOf(Object.values(EnumName)) generation | | types | Record<string, TypeOverride> | Custom schema factories per OpenAPI type or type:format |

Custom Type Factories

Override yup factories for specific OpenAPI types. Format-specific keys ("string:date") take priority over base type keys ("string"):

yupGenerator({
  output: "src/generated/ofs",
  enumImport: "@/api/generated/backend/index.schemas",
  types: {
    string: {
      factory: "string()",
      import: { name: "string", from: "@/utils/validation/types" },
    },
    "string:date": {
      factory: "dateString()",
      import: { name: "dateString", from: "@/utils/validation/date-string" },
    },
  },
})

See the full plugin documentation for react-hook-form integration, context passing, nested fields, and field state behavior details.