Prismix

The Prisma schema mixer 🍹

Made for Prisma ^2.0

Prisma restricts your schema to a single file, Prismix allows you to write as many schema files as you'd like, wherever you like—all while supporting cross-file model relations 🤯

Learn more about Prisma: prisma.io

Unlike prisma-merge, Prismix allows model relations to exist between files by combining models and enums, allowing you to extend and override Models as you please. This is ideal when working in a monorepo where parts of your schema need to exist in separate modules.

Installation

1. Install Prismix

yarn add prismix --dev

or NPM

npm install prismix --dev

2. Create a prismix.config.json file in the root of your project. This allows you to define how you would like Prismix to merge your schemas.

{
  "mixers": [
    {
        "input": [
            "base.prisma",
            "./modules/auth/auth.prisma", 
            "./modules/posts/posts.prisma",
        ],
        "output": "prisma/schema.prisma"
    }
  ]
}

The order of your input files effects how overrides are considered, the later inputs take priority over the earlier inputs.

The default output value is prisma/schema.prisma (it can be omitted from the config) and Prisma encourages you to keep is as such, especially if you want to use prisma format.

3. Add the npx prismix command as a prefix to your package.json scripts.

{
  "name": "my-app",
  "version": "1.0.0",
  "scripts": {
    "prismix": "npx prismix && prisma format",
    "dev": "yarn prismix && ts-node server.ts",
  }
}

Or just run npx prismix from within the repo that contains the Prismix config file.

Using prisma format is optional, but I like clean code.

Note: If you are using a monorepo you won't be able to run this command from the root, if you add a script "prismix": "npx prismix" you could run yarn workspace my-app prismix.

Cross-file relations

In order to relate to a model defined in another file you must create an alias model. This is simply a model with only the @id field.

This is to ensure Prisma can parse the schema file, as Prismix uses the Prisma SDK to parse each file individually before merging models at field level.

model Post {
    id String @id @default(autoincrement())
}

In the above example Post would be a model defined in another schema, any fields added in this schema file will be merged with any Post model(s) in other schema files. The @id field is the only required field in an extended model, however you may add fields specific to a relation. (this is shown in greater detail below)

Example

Let's go over how Prismix merges schemas. We'll keep it simple with two schemas that need to relate to each other.

base.prisma

generator client {
    provider = "prisma-client-js"
}

datasource db {
    provider = "postgresql"
    url      = "postgresql://..."
}

model Account {
    id       Int    @id @default(autoincrement())
    username String
    email    String
    status   String

    @@map("accounts")
}

We've established our generator and datasource, as well as our first model, Account. It is required that these two definitions be present in at least one of your schemas.

posts.prisma

Now we'll create the Posts schema in a different file. In order for posts to relate to accounts we can define an empty model to represent the account.

model Post {
    id         Int     @id @default(autoincrement())
    title      String
    content    String
    account_id Int
    account    Account @relation(fields: [account_id], references: [id])

    @@map("posts")
}

model Account {
    id     Int @id
    posts  Post[]
}

When Prismix merges these two schemas the relations will be connected.

schema.prisma

This is the generated file, do not edit this file!

// *** GENERATED BY PRISMIX :: DO NOT EDIT ***

generator client {
    provider = "prisma-client-js"
}

datasource db {
    provider = "postgresql"
    url      = "postgresql://..."
}

model Account {
    id       Int    @id @default(autoincrement())
    username String
    email    String
    status   String
    posts    Post[]
}

model Posts {
    id         Int     @id @default(autoincrement())
    title      String
    content    String
    account_id Int
    account    Account @relation(fields: [account_id], references: [id])

    @@map("posts")
}

As you can see the property posts was added on to the original Account schema and the account relation on the Posts schema links to the original Account schema.

How it works

Using the Prisma SDK we parse the input schemas into a DMMF objects, then process the schema merge into a single DMMF object as per the config file, finally it is converted back into Prisma schema format using a custom deserializer, adapted from @IBM/prisma-schema-transformer and written to the output location.

To-do

• Make it work
• Add glob support for wildcard schema discovery
• Make prismix.config.json optional
• Add command flags

Created by @jamiepine