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"
       // Optionally generate runtime enums to a separate file
        enumFileName = "enums.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
enumFileName	The filename for the generated enums. Omitting this will generate enums and files in the same file.
camelCase	Enable support for Kysely's camelCase plugin
readOnlyIds	Use Kysely's GeneratedAlways for @id fields with default values, preventing insert and update.
[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.

Per-field type overrides

In some cases, you might want to override a type for a specific field. This could be useful, for example, for constraining string types to certain literal values. Be aware though that this does not of course come with any runtime validation, and in most cases won't be guaranteed to match the actual data in the database.

That disclaimer aside, here's how it works: Add a @kyselyType(...) declaration to the Prisma docstring (deliniated using three slashes ///) for the field with your type inside the parentheses.

model User {
  id          String @id
  name        String

  /// @kyselyType('member' | 'admin')
  role        String
}

The parentheses can include any valid TS type declaration.

The output for the example above would be as follows:

export type User = {
  id: string;
  name: string;
  role: "member" | "owner";
};

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.

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 creating prisma/schema.prisma, running yarn prisma generate and checking the output in prisma/types.ts. The provider must be set as follows to reference the dev build:

   generator kysely {
       provider = "node ./dist/bin.js"
   }

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!
• Igal Klebanov (@igalklebanov) and Jökull Sólberg (@jokull) for being this library's main proponents on Twitter!
• The authors and maintainers of Kysely ❤️‍🔥

+ Boyce-Codd gang unite! 💽