@supabase/auth-helpers-sveltekit (BETA)

This submodule provides convenience helpers for implementing user authentication in SvelteKit applications.

Installation

Using npm:

npm install @supabase/auth-helpers-sveltekit

This library supports the following tooling versions:

• Node.js: ^16.15.0

Getting Started

Configuration

Set up the fillowing env vars. For local development you can set them in a .env file. See an example here.

# Find these in your Supabase project settings > API
PUBLIC_SUPABASE_URL=https://your-project.supabase.co
PUBLIC_SUPABASE_ANON_KEY=your-anon-key

SupabaseClient setup

Create a server supabase client in a handle hook:

// src/hooks.server.ts
import { PUBLIC_SUPABASE_URL, PUBLIC_SUPABASE_ANON_KEY } from '$env/static/public';
import { createSupabaseServerClient } from '@supabase/auth-helpers-sveltekit';
import type { Handle } from '@sveltejs/kit';

export const handle: Handle = async ({ event, resolve }) => {
  event.locals.supabase = createSupabaseServerClient({
    supabaseUrl: PUBLIC_SUPABASE_URL,
    supabaseKey: PUBLIC_SUPABASE_ANON_KEY,
    event
  });

  /**
   * a little helper that is written for convenience so that instead
   * of calling `const { data: { session } } = await supabase.auth.getSession()`
   * you just call this `await getSession()`
   */
  event.locals.getSession = async () => {
    const {
      data: { session }
    } = await event.locals.supabase.auth.getSession();
    return session;
  };

  return resolve(event, {
    filterSerializedResponseHeaders(name) {
      return name === 'content-range';
    }
  });
};

Note that we are specifying filterSerializedResponseHeaders here. We need to tell SvelteKit that supabase needs the content-range header.

Send session to client

In order to make the session available to the UI (pages, layouts) we need to pass the session in the root layout server load function:

// src/routes/+layout.server.ts
import type { LayoutServerLoad } from './$types';

export const load: LayoutServerLoad = async ({ locals: { getSession } }) => {
  return {
    session: getSession()
  };
};

Shared Load functions and pages

To be able to use Supabase in shared load functions and inside pages you need to create a Supabase client in the root layout load:

// src/routes/+layout.ts
import { PUBLIC_SUPABASE_ANON_KEY, PUBLIC_SUPABASE_URL } from '$env/static/public';
import { createSupabaseLoadClient } from '@supabase/auth-helpers-sveltekit';
import type { LayoutLoad } from './$types';
import type { Database } from '../DatabaseDefinitions';

export const load: LayoutLoad = async ({ fetch, data, depends }) => {
  depends('supabase:auth');

  const supabase = createSupabaseLoadClient<Database>({
    supabaseUrl: PUBLIC_SUPABASE_URL,
    supabaseKey: PUBLIC_SUPABASE_ANON_KEY,
    event: { fetch },
    serverSession: data.session
  });

  const {
    data: { session }
  } = await supabase.auth.getSession();

  return { supabase, session };
};

The client can be accessed inside pages by $page.data.supabase or data.supabase when using export let data: PageData.

The usage of depends tells sveltekit that this load function should be executed whenever invalidate is called to keep the page store in sync.

createSupabaseLoadClient caches the client when running in a browser environment and therefore does not create a new client for every time the load function runs.

Setting up the event listener on the client side

We need to create an event listener in the root +layout.svelte file in order catch supabase events being triggered.

<!-- src/routes/+layout.svelte -->
<script lang="ts">
  import { invalidate } from '$app/navigation';
  import { onMount } from 'svelte';
  import type { LayoutData } from './$types';

  export let data: LayoutData;

  $: ({ supabase, session } = data);

  onMount(() => {
    const {
      data: { subscription },
    } = supabase.auth.onAuthStateChange((event, _session) => {
      if (_session?.expires_at !== session?.expires_at) {
        invalidate('supabase:auth');
      }
    });

    return () => subscription.unsubscribe();
  });
</script>

<slot />

The usage of invalidate tells sveltekit that the root +layout.ts load function should be executed whenever the session updates to keep the page store in sync.

Generate types from your database

In order to get the most out of TypeScript and it´s intellisense, you should import the generated Database types into the app.d.ts type definition file that comes with your SvelteKit project, where import('./DatabaseDefinitions') points to the generated types file outlined in v2 docs here after you have logged in, linked, and generated types through the Supabase CLI.

// src/app.d.ts

import { SupabaseClient, Session } from '@supabase/supabase-js';
import { Database } from './DatabaseDefinitions';

declare global {
  namespace App {
    interface Locals {
      supabase: SupabaseClient<Database>;
      getSession(): Promise<Session | null>;
    }
    interface PageData {
      session: Session | null;
    }
    // interface Error {}
    // interface Platform {}
  }
}

Client-side data fetching with RLS

For row level security to work properly when fetching data client-side, you need to use supabaseClient from PageData and only run your query once the session is defined client-side:

<!-- src/routes/profile/+page.svelte -->
<script lang="ts">
  import type { PageData } from './$types';

  export let data: PageData;

  $: ({ supabase, session } = data);

  let loadedData = [];
  async function loadData() {
    const { data } = await supabase.from('test').select('*').limit(20);
    loadedData = data;
  }

  $: if (session) {
    loadData();
  }
</script>

{#if session}
<p>client-side data fetching with RLS</p>
<pre>{JSON.stringify(loadedData, null, 2)}</pre>
{/if}

Server-side data fetching with RLS

<!-- src/routes/profile/+page.svelte -->
<script lang="ts">
  import type { PageData } from './$types';

  export let data: PageData;
  $: ({ user, tableData } = data);
</script>

<div>Protected content for {user.email}</div>
<pre>{JSON.stringify(tableData, null, 2)}</pre>
<pre>{JSON.stringify(user, null, 2)}</pre>

// src/routes/profile/+page.ts
import type { PageLoad } from './$types';
import { redirect } from '@sveltejs/kit';

export const load: PageLoad = async ({ parent }) => {
  const { supabase, session } = await parent();
  if (!session) {
    throw redirect(303, '/');
  }
  const { data: tableData } = await supabase.from('test').select('*');

  return {
    user: session.user,
    tableData
  };
};

Protecting API routes

Wrap an API Route to check that the user has a valid session. If they're not logged in the session is null.

// src/routes/api/protected-route/+server.ts
import type { RequestHandler } from './$types';
import { json, error } from '@sveltejs/kit';

export const GET: RequestHandler = async ({ locals: { supabase, getSession } }) => {
  const session = await getSession();
  if (!session) {
    // the user is not signed in
    throw error(401, { message: 'Unauthorized' });
  }
  const { data } = await supabase.from('test').select('*');

  return json({ data });
};

If you visit /api/protected-route without a valid session cookie, you will get a 401 response.

Protecting Actions

Wrap an Action to check that the user has a valid session. If they're not logged in the session is null.

// src/routes/posts/+page.server.ts
import type { Actions } from './$types';
import { error, fail } from '@sveltejs/kit';

export const actions: Actions = {
  createPost: async ({ request, locals: { supabase, getSession } }) => {
    const session = await getSession();

    if (!session) {
      // the user is not signed in
      throw error(401, { message: 'Unauthorized' });
    }
    // we are save, let the user create the post
    const formData = await request.formData();
    const content = formData.get('content');

    const { error: createPostError, data: newPost } = await supabase
      .from('posts')
      .insert({ content });

    if (createPostError) {
      return fail(500, {
        supabaseErrorMessage: createPostError.message
      });
    }
    return {
      newPost
    };
  }
};

If you try to submit a form with the action ?/createPost without a valid session cookie, you will get a 401 error response.

Saving and deleting the session

import type { Actions } from './$types';
import { fail, redirect } from '@sveltejs/kit';
import { AuthApiError } from '@supabase/supabase-js';

export const actions: Actions = {
  signin: async ({ request, locals: { supabase } }) => {
    const formData = await request.formData();

    const email = formData.get('email') as string;
    const password = formData.get('password') as string;

    const { error } = await supabase.auth.signInWithPassword({
      email,
      password
    });

    if (error) {
      if (error instanceof AuthApiError && error.status === 400) {
        return fail(400, {
          error: 'Invalid credentials.',
          values: {
            email
          }
        });
      }
      return fail(500, {
        error: 'Server error. Try again later.',
        values: {
          email
        }
      });
    }

    throw redirect(303, '/dashboard');
  },

  signout: async ({ locals: { supabase } }) => {
    await supabase.auth.signOut();
    throw redirect(303, '/');
  }
};

Protecting multiple routes

To avoid writing the same auth logic in every single route you can use the handle hook to protect multiple routes at once.

// src/hooks.server.ts
import type { RequestHandler } from './$types';
import { getSupabase } from '@supabase/auth-helpers-sveltekit';
import { redirect, error } from '@sveltejs/kit';

export const handle: Handle = async ({ event, resolve }) => {
  // protect requests to all routes that start with /protected-routes
  if (event.url.pathname.startsWith('/protected-routes')) {
    const session = await event.locals.getSession();
    if (!session) {
      // the user is not signed in
      throw redirect(303, '/');
    }
  }

  // protect POST requests to all routes that start with /protected-posts
  if (event.url.pathname.startsWith('/protected-posts') && event.request.method === 'POST') {
    const session = await event.locals.getSession();
    if (!session) {
      // the user is not signed in
      throw error(303, '/');
    }
  }

  return resolve(event);
};