prisma-kysely

🚧 Library and README in progress...

Do you like Prisma's migration flow, schema language and DX but not the limitations of the Prisma Client? Do you want to harness the raw power of SQL without losing the safety of the TypeScript type system?

Enter prisma-kysely!

Setup

1. Install prisma-kysely using your package manager of choice:

   yarn add prisma-kysely
   

2. Replace (or augment) the default client generator in your schema.prisma file with the following:

   generator kysely {
       provider = "prisma-kysely"
   
       // Optionally provide a destination directory for the generated file
       // and a filename of your choice
       output = "../src/db"
       fileName = "types.ts"
   }
   

3. Run prisma migrate dev or prisma generate and use your freshly generated types when instantiating Kysely!

Motivation

Prisma's migration and schema definition workflow is undeniably great, and the typesafety of the Prisma client is top notch, but there comes a time in every Prisma user's life where the client becomes just a bit too limiting. Sometimes we just need to write our own multi table joins and squeeze that extra drop of performance out of our apps. The Prisma client offers two options: using their simplified query API or going all-in with raw SQL strings, sacrificing type safety.

This is where Kysely shines. Kysely provides a toolbox to write expressive, type-safe SQL queries with full autocompletion. The problem with Kysely though is that it's not super opinionated when it comes to schema definition and migration. What many users resort to is using something like Prisma to define the structure of their databases, and kysely-codegen to introspect their databases post-migration.

This package, prisma-kysely, is meant as a more integrated and convenient way to keep Kysely types in sync with Prisma schemas. After making the prerequisite changes to your schema file, it's just as convenient and foolproof as using Prisma's own client.

I've been using this combo for a few months now in tandem with Cloudflare's D1 for my private projects and Postgres at work. It's been a game-changer, and I hope it's just as useful for you! 😎

Config

Key	Description
output	The directory where generated code will be saved
fileName	The filename for the generated file
[typename]TypeOverride	Allows you to override the resulting TypeScript type for any Prisma type. Useful when targeting a different environment than Node (e.g. WinterCG compatible runtimes that use UInt8Arrays instead of Buffers for binary types etc.) Check out the config validator for a complete list of options.

Gotchas

Default values

By default (no pun intended) the Prisma Query Engine uses JS based implementations for certain default values, namely: uuid() and cuid(). This means that they don't end up getting defined as default values on the database level, and end up being pretty useless for us.

Prisma does provide a nice solution to this though, in the form of dbgenerated(). This allows us to use any valid default value expression that our database supports:

model PostgresUser {
   id    String @id @default(dbgenerated("gen_random_uuid()"))
}

model SQLiteUser {
   id    String @id @default(dbgenerated("uuid()"))
}

Check out the Prisma Docs for more info.

Field level @map not supported

Regrettably, prisma-kysely doesn't support mapping field names to different columns. This is due the fact that Prisma's "Data Model Meta Format" doesn't supply custom generators with the info needed. There's no easy way to implement this besides re-parsing the schema ourselves, so for now we have to wait until Prisma fix this upstream. We're keeping track of the issue here: https://github.com/valtyr/prisma-kysely/issues/4. In the meantime you can get around the issue by naming the field directly after the column.

Contributions

OMG you actually want to contribute? I'm so thankful! 🙇‍♂️

Here's everything you need to do (let me know if something's missing...)

1. Fork and pull the repository
2. Run yarn install and yarn dev to start tsc in watch mode.
3. Make changes to the source code
4. Test your changes by editing prisma/schema.prisma, running yarn prisma generate and checking the output in prisma/types.ts.
5. Create a pull request! If your changes make sense, I'll try my best to review and merge them quickly.

I'm not 100% sure the type maps are correct for every dialect, so any and all contributions on that front would be greatly appreciated. The same goes for any bug you come across or improvement you can think of.

Shoutouts

• I wouldn't have made this library if I hadn't used Robin Blomberg's amazing Kysely Codegen. For anyone that isn't using Prisma for migrations I wholeheartedly recommend his package.
• The implicit many-to-many table generation code is partly inspired by and partly stolen from prisma-dbml-generator. Many-too-many thanks to them!
• Jökull Sólberg (@jokull) for being this library's main proponent on Twitter!

+ Boyce-Codd gang unite! 💽