Zod Validation plugin

A plugin for adding validation for field arguments based on zod. This plugin does not expose zod directly, but most of the options map closely to the validations available in zod.

Usage

Install

To use the zod plugin you will need to install both zod package and the zod plugin:

npm install --save zod @pothos/plugin-zod

Setup

import ZodPlugin from '@pothos/plugin-zod';
const builder = new SchemaBuilder({
  plugins: [ZodPlugin],
  zod: {
    // optionally customize how errors are formatted
    validationError: (zodError, args, context, info) => {
      // the default behavior is to just throw the zod error directly
      return zodError;
    },
  },
});
 
builder.queryType({
  fields: (t) => ({
    simple: t.boolean({
      args: {
        // Validate individual args
        email: t.arg.string({
          validate: {
            email: true,
          },
        }),
        phone: t.arg.string(),
      },
      // Validate all args together
      validate: (args) => !!args.phone || !!args.email,
      resolve: () => true,
    }),
  }),
});

Options

validationError: (optional) A function that will be called when validation fails. The function will be passed the the zod validation error, as well as the args, context and info objects. It can throw an error, or return an error message or custom Error instance.

Examples

With custom message

builder.queryType({
  fields: (t) => ({
    withMessage: t.boolean({
      args: {
        email: t.arg.string({
          validate: {
            email: [true, { message: 'invalid email address' }],
          },
        }),
        phone: t.arg.string(),
      },
      validate: [
        (args) => !!args.phone || !!args.email,
        { message: 'Must provide either phone number or email address' },
      ],
      resolve: () => true,
    }),
  }),
});

Validating List

builder.queryType({
  fields: (t) => ({
    list: t.boolean({
      args: {
        list: t.arg.stringList({
          validate: {
            items: {
              email: true,
            },
            maxLength: 3,
          },
        }),
      },
      resolve: () => true,
    }),
  }),
});

Using your own zod schemas

If you just want to use a zod schema defined somewhere else, rather than using the validation options you can use the schema option:

builder.queryType({
  fields: (t) => ({
    list: t.boolean({
      args: {
        max5: t.arg.int({
          validate: {
            schema: zod.number().int().max(5),
          },
        }),
      },
      resolve: () => true,
    }),
  }),
});

You can also validate all arguments together using a zod schema:

builder.queryType({
  fields: (t) => ({
    simple: t.boolean({
      args: {
        email: t.arg.string(),
        phone: t.arg.string(),
      },
      // Validate all args together using own zod schema
      validate: {
        schema: zod.object({
          email: zod.string().email(),
          phone: zod.string(),
        }),
      },
      resolve: () => true,
    }),
  }),
});

API

On Object fields (for validating field arguments)

• validate: Refinement<T> | Refinement<T>[] | ValidationOptions.

On InputObjects (for validating all fields of an input object)

• validate: Refinement<T> | Refinement<T>[] | ValidationOptions.

On arguments or input object fields (for validating a specific input field or argument)

• validate: Refinement<T> | Refinement<T>[] | ValidationOptions.

Refinement

A Refinement is a function that will be passed to the zod refine method. It receives the args object, input object, or value of the specific field the refinement is defined on. It should return a boolean or Promise<boolean>.

Refinements can either be just a function: (val) => isValid(val), or an array with the function, and an options object like: [(val) => isValid(val), { message: 'field should be valid' }].

The options object may have a message property, and if the type being validated is an object, it can also include a path property with an array of strings indicating the path of the field in the object being validated. See the zod docs on refine for more details.

ValidationOptions

The validation options available depend on the type being validated. Each property of ValidationOptions can either be a value specific to the constraint, or an array with the value, and the options passed to the underlying zod method. This options object can be used to set a custom error message:

{
  validate: {
    max: [10, { message: 'should not be more than 10' }],
    int: true,
  }
}

Number

• type?: 'number'
• refine?: Refinement<number> | Refinement<number>[]
• min?: Constraint<number>
• max?: Constraint<number>
• positive?: Constraint<boolean>
• nonnegative?: Constraint<boolean>
• negative?: Constraint<boolean>
• nonpositive?: Constraint<boolean>
• int?: Constraint<boolean>
• schema?: ZodSchema<number>

BigInt

• type?: 'bigint'
• refine?: Refinement<bigint> | Refinement<bigint>[]
• schema?: ZodSchema<bigint>

Boolean

• type?: 'boolean'
• refine?: Refinement<boolean> | Refinement<boolean>[]
• schema?: ZodSchema<boolean>

Date

• type?: 'boolean'
• refine?: Refinement<boolean> | Refinement<boolean>[]
• schema?: ZodSchema<Date>

String

• type?: 'string';
• refine?: Refinement<string> | Refinement<string>[]
• minLength?: Constraint<number>
• maxLength?: Constraint<number>
• length?: Constraint<number>
• url?: Constraint<boolean>
• uuid?: Constraint<boolean>
• email?: Constraint<boolean>
• regex?: Constraint<RegExp>
• schema?: ZodSchema<string>

Object

• type?: 'object';
• refine?: Refinement<T> | Refinement<T>[]
• schema?: ZodSchema<Ts>

Array

• type?: 'array';
• refine?: Refinement<T[]> | Refinement<T[]>[]
• minLength?: Constraint<number>
• maxLength?: Constraint<number>
• length?: Constraint<number>
• items?: ValidationOptions<T> | Refinement<T>
• schema?: ZodSchema<T[]>

How it works

Each arg on an object field, and each field on an input type with validation will build its own zod validator. These validators will be a union of all potential types that can apply the validations defined for that field. For example, if you define an optional field with a maxLength validator, it will create a zod schema that looks something like:

zod.union([zod.null(), zod.undefined(), zod.array().maxLength(5), zod.string().maxLength(5)]);

If you set and email validation instead the schema might look like:

zod.union([zod.null(), zod.undefined(), zod.string().email()]);

At runtime, we don't know anything about the types being used by your schema, we can't infer the expected js type from the type definition, so the best we can do is limit the valid types based on what validations they support. The type validation allows explicitly validating the type of a field to be one of the base types supported by zod:

// field
{
validate: {
  type: 'string',
  maxLength: 5
}
// generated
zod.union([zod.null(), zod.undefined(), zod.string().maxLength(5)]);

There are a few exceptions the above:

1. args and input fields that are InputObjects always use zod.object() rather than creating a union of potential types.

2. args and input fields that are list types always use zod.array().

3. If you only include a refine validation (or just pass a function directly to validate) we will just use zods unknown validator instead:

// field
{
  validate: (val) => isValid(val),
}
// generated
zod.union([zod.null(), zod.undefined(), zod.unknown().refine((val) => isValid(val))]);

If the validation options include a schema that schema will be used as an intersection wit the generated validator:

// field
{
  validate: {
    int: true,
    schema: zod.number().max(10),
}
// generated
zod.union([zod.null(), zod.undefined(),  zod.intersection(zod.number().max(10), zod.number().int())]);

Sharing schemas with client code

The easiest way to share validators is the use the to define schemas for your fields in an external file using the normal zod APIs, and then attaching those to your fields using the schema option.

// shared
import { ValidationOptions } from '@pothos/plugin-zod';
 
const numberValidation = zod.number().max(5);
 
// server
builder.queryType({
  fields: (t) => ({
    example: t.boolean({
      args: {
        num: t.arg.int({
          validate: {
            schema: numberValidation,
          }
        }),
      },
      resolve: () => true,
    }),
  });
});
 
// client
numberValidator.parse(3) // pass
numberValidator.parse('3') // fail

You can also use the createZodSchema helper from the plugin directly to create zod Schemas from an options object:

// shared
import { ValidationOptions } from '@pothos/plugin-zod';
 
const numberValidation: ValidationOptions<number> = {
  max: 5,
};
 
// server
builder.queryType({
  fields: (t) => ({
    example: t.boolean({
      args: {
        num: t.arg.int({
          validate: numberValidation,
        }),
      },
      resolve: () => true,
    }),
  });
});
 
// client
import { createZodSchema } from '@pothos/plugin-zod';
 
const validator = createZodSchema(numberValidator);
 
validator.parse(3) // pass
validator.parse('3') // fail