Nuxt Precognition

Nuxt Precognition is a validation module for Nuxt that implements the Precognition protocol in a backend-agnostic way. It supports any backend or validation library, and is not tied to Laravel.

Table of Contents

• Nuxt Precognition
  • Table of Contents
  • Requirements
  • Why Nuxt Precognition?
  • Quick Example
  • Features
  • Installation
  • How It Works
    • Define Zod Error Parser
    • Client Side Validation
    • Server Side Validation
  • Precognition Protocol
  • Configuration
    • Options
    • Status Handlers
  • Laravel Integration
  • Contributing
  • License

Requirements

• Nuxt >= 3.x
• Node.js >= 18

Why Nuxt Precognition?

• Backend agnostic: Works with any backend that supports the Precognition protocol.
• Validation library agnostic: Use Zod, Yup, or any other validation library.
• Client & server side validation: Seamless validation on both ends.
• Optimal TypeScript support: Typesafe forms and error handling.
• Highly customizable: Plug in your own error parsers and status handlers.

Quick Example

interface User {
  email: string
  password: string
}

const form = useForm(
  (): User => ({ email: '', password: '' }),
  (body, headers) => $fetch('/api/login', { method: 'POST', headers, body })
)

Features

• Laravel compliant
• Validation library agnostic
• Client and server side validation
• TypeScript support
• Customizable error parsing and status handling

Installation

Install the module in your Nuxt app:

npx nuxi module add nuxt-precognition

How It Works

The core concept is error parsers: functions that extract validation errors from thrown errors.

type ValidationErrors = Record<string, string | string[]>

interface ValidationErrorsData {
  message: string
  errors: ValidationErrors
}

type ValidationErrorParser = (error: Error) => ValidationErrorsData | undefined | null

Define Zod Error Parser

// app/utils/precognition.ts or shared/utils/precognition.ts
import { ZodError } from 'zod'

export const zodPrecognitionErrorParser: ValidationErrorParser = (error) => {
  if (error instanceof ZodError) {
    const errors: Record<string, string[]> = {}
    for (const issue of error.issues) {
      const key = issue.path.join('.')
      if (key in errors) {
        errors[key].push(issue.message)
        continue
      }
      errors[key] = [issue.message]
    }
    return { errors, message: error.message }
  }
  return null
}

Note:
For Server side validation, place this file in shared/utils folder.

Client Side Validation

Add the parser client side globally.

// app/plugins/precognition.ts
export default defineNuxtPlugin(() => {
  const { $precognition } = useNuxtApp()

  $precognition.errorParsers.push(zodErrorParser)

  // ..
})

Use the composable in setup method.

const UserSchema = z.object({
  email: z.string().email(),
  password: z.string().min(8),
})

const form = useForm(
  (): z.infer<typeof UserSchema> => ({
    email: '',
    password: '',
  }),
  (body, headers) => $fetch('/api/login', {
    method: 'POST',
    headers,
    body,
  }),
  {
    clientValidation(data) {
      UserSchema.parse(data)
    },
  },
)

function login() {
  form.submit()
}

function reset() {
  form.reset()
  document.getElementById('email')?.focus()
}

<form
  @submit.prevent="login"
  @reset.prevent="reset"
>
  <div>
    <label for="email">Email address</label>
    <input
      id="email"
      v-model="form.email"
      name="email"
      type="email"
      @change="form.validate('email')"
    >
    <span v-if="form.valid('email')">OK!!</span>
    <span v-if="form.invalid('email')">{{ form.errors.email }}</span>
  </div>

  <div>
    <label for="password">Password</label>
    <input
      id="password"
      v-model="form.password"
      name="password"
      type="password"
      autocomplete="current-password"
      required
      @change="form.validate('password')"
    >
    <span v-if="form.valid('password')">OK!!</span>
    <span v-if="form.invalid('password')">{{ form.errors.password }}</span>
  </div>

  <div>
    <button type="submit">Sign in</button>
    <button type="reset">Reset</button>
  </div>
</form>

Server Side Validation

1. update the default configuration.

// nuxt.config.ts

export default defineNuxtConfig({
  modules: [
    'nuxt-precognition'
  ],
  precognition: {
    backendValidation: true, 
    enableNuxtClientErrorParser: true,
  },
})

2. Create a Nitro plugin to parse server errors:

// server/plugins/precognition.ts
import { ZodError } from 'zod'

export default defineNitroPlugin((nitroApp) => {
  nitroApp.hooks.hook('request', (event) => {
    event.context.$precognition.errorParsers = [
      zodErrorParser
    ]
  })
})

3. Use definePrecognitiveEventHandler in the object way and add validation in the onRequest hook.

// server/api/login.post.ts
import { z } from 'zod'
import { definePrecognitiveEventHandler, readBody } from '#imports'

const loginSchema = z.object({
  email: z.string().email(),
  password: z.string()
}).refine((_data) => {
  // Check for email and password match
  // ...
  return true
},
{ message: 'invalid credentials', path: ['email'] },
)

export default definePrecognitiveEventHandler({
  async onRequest(event) {
    const body = await readBody(event)
    loginSchema.parse(body)
  },
  handler: () => {
    return {
      status: 200,
      body: {
        message: 'Success',
      },
    }
  },
})

Precognition Protocol

If you need to define your own backend logic outside Nitro, follow these requirements.

• Precognitive Requests must have:
  1. Precognitive Header { 'Precognitive': 'true' }
• To validate specific variables, each keys must be specified inside the ValidateOnly Header, comma separated and leveraging dot notation { 'Precognition-Validate-Only': 'name,age,address.street,address.number' }
• To validate the full Form the ValidateOnly Header should be omitted or define as an empty string.
• Successful validation response must have:
  1. Precognitive Header { 'Precognitive': 'true' }
  2. Precognitive Successful Header { 'Precognition-Success': 'true' }
  3. Precognitive Successful status code: 204
• Error validation response must have:
  1. Precognitive Header { 'Precognitive': 'true' }
  2. Precognition-Validate-Only header if needed { 'Precognition-Validate-Only': 'name,age,address.street,address.number' }
  3. Validation Error status code: 422
  4. Validation Errors and Message will be parsed as per your define logic, or using standard errorParsers:
     • NuxtErrorParsers: NuxtPrecognitiveErrorResponse: Response & { _data: { data: ValidationErrorsData }}
     • LaravelErrorParsers: LaravelPrecognitiveErrorResponse: Response & { _data: ValidationErrorsData }

Configuration

Add to your nuxt.config.ts:

export default defineNuxtConfig({
  modules: ['nuxt-precognition'],
  precognition: {
    backendValidation: true,
    enableNuxtClientErrorParser: true,
    // ...other options
  }
})

Options

| name | type | default | description | |---|---|---|---| |validationTimeout|number|1500|Debounce time, in milliseconds, between two precognitive validation requests.| |backendValidation|boolean|false|Flag to enable the precognitive validation.| |validateFiles|boolean|false|Flag to enable files validation on precognitive requests.| |enableNuxtClientErrorParser|boolean|false|Flag to enable nuxtErrorParsers on client side (in form.validate and form.submit).| |enableLaravelClientErrorParser|boolean|false|Flag to enable laravelErrorParsers on client side (in form.validate and form.submit).| |enableLaravelServerErrorParser|boolean|false|Flag to enable laravelErrorParsers on server side (in definePrecognitiveEventHandler).|

Status Handlers

Like in official package, you can define globally, or @instance level, custom handlers for specific error codes:

// plugins/precognition.ts

export default defineNuxtPlugin(() => {
  const { $precognition } = useNuxtApp()

  $precognition.statusHandlers = {
    401: async (error, form) => {
      form.error = createError('Unauthorized')
      await navigateTo('/login')
    },
    403: async (error, form) => {
      form.error = createError('Forbidden')
    },
  }
})

Laravel Integration

If you want to use Laravel, you won't need nuxt nitro integration.

1. Enable Backend Validation and Error Parsers:

// nuxt.config.ts
export default defineNuxtConfig({
  modules: ['nuxt-precognition'],
  precognition: {
    backendValidation: true,
    enableLaravelClientErrorParser: true,
  }
})

2. Plugin Example:

Add Sanctum token prefetch and ensure proper handling of all precognitive requests.

// plugins/laravel.ts
export default defineNuxtPlugin((app) => {
  const { $precognition } = useNuxtApp()
  const token = useCookie('XSRF-TOKEN')

  const api = $fetch.create({
    baseURL: 'http://localhost',
    credentials: 'include',
    headers: {
      'Accept': 'application/json',
      'Content-Type': 'application/json',
    },
    onRequest: ({ options }) => {
      if (token.value) {
        const headers = new Headers(options.headers)
        headers.set('X-XSRF-TOKEN', token.value)
        options.headers = headers
      }
    },
    onResponse: (context) => {
      // ensure non false positive validations
      $precognition.assertSuccessfulPrecognitiveResponses(context)
    },
  })

  async function fetchSanctumToken() {
    try {
      await api('/sanctum/csrf-cookie')
      token.value = useCookie('XSRF-TOKEN').value
      if (!token.value) throw new Error('Failed to get CSRF token')
    } catch (e) {
      console.error(e)
    }
  }

  app.hook('app:mounted', fetchSanctumToken)

  return {
    provide: {
      api,
      sanctum: {
        fetchToken: fetchSanctumToken,
        token,
      },
    },
  }
})

3. Laravel CORS Configuration:

Ensure Precognitive headers will be shared with Nuxt application.

// config/cors.php
return [
  'paths' => ['*'],
  'allowed_methods' => ['*'],
  'allowed_origins' => ['*'],
  'allowed_origins_patterns' => [env('FRONTEND_URL', 'http://localhost:3000')],
  'allowed_headers' => ['*'],
  'exposed_headers' => ['Precognition', 'Precognition-Success'],
  'max_age' => 0,
  'supports_credentials' => true,
];

4. Enable Precognition Middleware:

Apply precognitive middleware where needed.

// routes/api.php
Route::middleware('precognitive')->group(function () {
    Route::apiResource('posts', \App\Http\Controllers\PostController::class);
});

That's it. Nuxt validation will be in sync with Laravel!!.

Contributing

# Install dependencies
npm install

# Generate type stubs
npm run dev:prepare

# Develop with the playground
npm run dev

# Build the playground
npm run dev:build

# Run ESLint
npm run lint

# Run Vitest
npm run test
npm run test:watch

# Release new version
npm run release

License

MIT © [sot1986]