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tRPC-SvelteKit
End-to-end typesafe APIs with tRPC.io in SvelteKit applications.
No code generation, run-time bloat, or build pipeline.
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See below.
Key features
@sveltejs/adapter-node & @sveltejs/adapter-vercel
load() function for SSR
Example application with Prisma & superjson
TL;DR
Add this in your SvelteKit app hooks:
// src/hooks.ts
import { createTRPCHandle } from 'trpc-sveltekit';
// create your tRPC router...
export const handle = createTRPCHandle({ url: '/trpc', router }); // π add this handle
How to use
- Install this package
npm install trpc-sveltekit/yarn add trpc-sveltekit
// $lib/trpcServer.ts
import type { inferAsyncReturnType } from '@trpc/server';
import * as trpc from '@trpc/server';
// optional
export const createContext = () => {
// ...
return {
/** context data */
};
};
// optional
export const responseMeta = () => {
// ...
return {
// { headers: ... }
};
};
export const router = trpc
.router<inferAsyncReturnType<typeof createContext>>()
// queries and mutations...
.query('hello', {
resolve: () => 'world',
});
export type Router = typeof router;
- Add this handle to your application hooks (
src/hooks.tsorsrc/hooks/index.ts):
// src/hooks.ts or src/hooks/index.ts
import { createContext, responseMeta, router } from '$lib/trpcServer';
import { createTRPCHandle } from 'trpc-sveltekit';
export const handle = createTRPCHandle({
url: '/trpc', // optional; defaults to '/trpc'
router,
createContext, // optional
responseMeta, // optional
});
Learn more about SvelteKit hooks here.
- Create a tRPC client:
// $lib/trpcClient.ts
import type { Router } from '$lib/trpcServer'; // π only the types are imported from the server
import * as trpc from '@trpc/client';
export default trpc.createTRPCClient<Router>({ url: '/trpc' });
- Use the client like so:
// page.svelte
import trpcClient from '$lib/trpcClient';
const greeting = await trpcClient.query('hello');
console.log(greeting); // => π world
Recipes & caveats
π
Usage with Prisma
When you're building your SvelteKit app for production, you must instantiate your Prisma client like this:
// $lib/prismaClient.ts
import pkg from '@prisma/client';
const { PrismaClient } = pkg;
const prismaClient = new PrismaClient();
export default prismaClient;
This will not work:
// $lib/prismaClient.ts
import { PrismaClient } from '@prisma/client';
const prismaClient = new PrismaClient();
export default prismaClient;
Configure superjson to correctly handle Decimal.js / Prisma.Decimal
By default, superjson only supports built-in data types to keep the bundle-size as small as possible. Here's how you could extend it with Decimal.js / Prisma.Decimal support:
// $lib/trpcTransformer.ts
import Decimal from 'decimal.js';
import superjson from 'superjson';
superjson.registerCustom<Decimal, string>(
{
isApplicable: (v): v is Decimal => Decimal.isDecimal(v),
serialize: (v) => v.toJSON(),
deserialize: (v) => new Decimal(v),
},
'decimal.js'
);
export default superjson;
Then, configure your tRPC router like so:
// $lib/trpcServer.ts
import trpcTransformer from '$lib/trcpTransformer';
import * as trpc from '@trpc/server';
export const router = trpc
.router()
// .merge, .query, .mutation, etc.
.transformer(trpcTransformer); // π
export type Router = typeof router;
...and don't forget to configure your tRPC client:
// $lib/trpcClient.ts
import type { Router } from '$lib/trpcServer';
import transformer from '$lib/trpcTransformer';
import * as trpc from '@trpc/client';
export default trpc.createTRPCClient<Router>({
url: '/trpc',
transformer, // π
});
svelte.config.js in order to be able to build your application for production with adapter-node/adapter-vercel:
// svelte.config.js
import adapter from '@sveltejs/adapter-node'; // or Vercel
import preprocess from 'svelte-preprocess';
/** @type {import('@sveltejs/kit').Config} */
const config = {
preprocess: preprocess(),
kit: {
adapter: adapter(),
vite:
process.env.NODE_ENV === 'production'
? {
ssr: {
noExternal: ['superjson'],
},
}
: undefined,
},
};
export default config;
Client-side helper types
It is often useful to wrap the functionality of your @trpc/client api within other functions. For this purpose, it's necessary to be able to infer input types, output types, and api paths generated by your @trpc/server router. Using tRPC's inference helpers, you could do something like:
// $lib/trpcClient.ts
import type { Router } from '$lib/trpcServer';
import trpcTransformer from '$lib/trpcTransformer';
import * as trpc from '@trpc/client';
import type { inferProcedureInput, inferProcedureOutput } from '@trpc/server';
export default trpc.createTRPCClient<Router>({
url: '/trpc',
transformer: trpcTransformer,
});
type Query = keyof Router['_def']['queries'];
type Mutation = keyof Router['_def']['mutations'];
// Useful types πππ
export type InferQueryOutput<RouteKey extends Query> = inferProcedureOutput<Router['_def']['queries'][RouteKey]>;
export type InferQueryInput<RouteKey extends Query> = inferProcedureInput<Router['_def']['queries'][RouteKey]>;
export type InferMutationOutput<RouteKey extends Mutation> = inferProcedureOutput<
Router['_def']['mutations'][RouteKey]
>;
export type InferMutationInput<RouteKey extends Mutation> = inferProcedureInput<Router['_def']['mutations'][RouteKey]>;
Then, you could use the inferred types like so:
// authors.svelte
<script lang="ts">
let authors: InferQueryOutput<'authors:browse'> = [];
const loadAuthors = async () => {
authors = await trpc.query('authors:browse', { genre: 'fantasy' });
};
</script>
Server-Side Rendering
If you need to use the tRPC client in SvelteKit's load() function for SSR, make sure to initialize it like so:
// $lib/trpcClient.ts
import { browser } from '$app/env';
import type { Router } from '$lib/trpcServer';
import * as trpc from '@trpc/client';
const client = trpc.createTRPCClient<Router>({
url: browser ? '/trpc' : 'http://localhost:3000/trpc', // π
});
Vercel's Edge Cache for Serverless Functions
Your server responses must satisfy some criteria in order for them to be cached Verced Edge Network, and here's where tRPC's responseMeta() comes in handy. You could initialize your handle in src/hooks.ts like so:
// src/hooks.ts or src/hooks/index.ts
import { router } from '$lib/trpcServer';
import { createTRPCHandle } from 'trpc-sveltekit';
export const handle = createTRPCHandle({
url: '/trpc',
router,
responseMeta({ type, errors }) {
if (type === 'query' && errors.length === 0) {
const ONE_DAY_IN_SECONDS = 60 * 60 * 24;
return {
headers: {
'cache-control': `s-maxage=1, stale-while-revalidate=${ONE_DAY_IN_SECONDS}`
}
};
}
return {};
}
});
Example
See an example with Prisma & superjson:
Stand with Ukraine
On 24th of February 2022 Russia unlawfully invaded Ukraine. This is an unjustified, unprovoked attack on the sovereignty of a neighboring country, but also an open affront to international peace and stability that has the potential to degenerate into a nuclear event threatening the very existence of humanity. I am an EU (Romanian) citizen, but I am doing everything in my power to stop this madness. I stand with Ukraine. The entire Svelte community
License
The ISC License.
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