@mrleebo/prisma-ast

What is @mrleebo/prisma-ast?

@mrleebo/prisma-ast is an npm package designed to parse and manipulate Prisma schema files. It provides an Abstract Syntax Tree (AST) representation of Prisma schema files, allowing developers to programmatically read, modify, and generate Prisma schema definitions.

What are @mrleebo/prisma-ast's main functionalities?

Parsing Prisma Schema

This feature allows you to parse a Prisma schema string into an AST. The code sample demonstrates how to parse a simple Prisma schema and output the resulting AST.

const { parseSchema } = require('@mrleebo/prisma-ast');
const schema = `
model User {
  id    Int     @id @default(autoincrement())
  name  String
}
`;
const ast = parseSchema(schema);
console.log(JSON.stringify(ast, null, 2));

Modifying Prisma Schema

This feature allows you to modify an existing Prisma schema by manipulating its AST. The code sample shows how to add a new field to the User model and then print the updated schema.

const { parseSchema, printSchema } = require('@mrleebo/prisma-ast');
let schema = `
model User {
  id    Int     @id @default(autoincrement())
  name  String
}
`;
let ast = parseSchema(schema);
ast.declarations[0].fields.push({
  name: 'email',
  type: 'String',
  attributes: []
});
schema = printSchema(ast);
console.log(schema);

Generating Prisma Schema

This feature allows you to generate a Prisma schema from an AST. The code sample demonstrates how to create an AST for a simple User model and then generate the corresponding Prisma schema string.

const { printSchema } = require('@mrleebo/prisma-ast');
const ast = {
  type: 'schema',
  declarations: [
    {
      type: 'model',
      name: 'User',
      fields: [
        { name: 'id', type: 'Int', attributes: [{ type: 'attribute', name: 'id' }, { type: 'attribute', name: 'default', args: [{ type: 'function', name: 'autoincrement' }] }] },
        { name: 'name', type: 'String', attributes: [] }
      ]
    }
  ]
};
const schema = printSchema(ast);
console.log(schema);

Other packages similar to @mrleebo/prisma-ast

prisma

The official Prisma ORM package. While it does not provide direct AST manipulation capabilities, it offers a comprehensive set of tools for working with databases using Prisma schema files. It focuses more on database interactions and migrations rather than schema parsing and manipulation.

prisma-schema-dsl

A package that provides a Domain Specific Language (DSL) for generating Prisma schema files. It allows for programmatic creation of Prisma schema definitions but does not offer the same level of AST manipulation as @mrleebo/prisma-ast.

prisma-dbml-generator

A package that converts Prisma schema files to DBML (Database Markup Language) format. It focuses on schema conversion rather than direct AST manipulation, making it useful for different use cases compared to @mrleebo/prisma-ast.

README

@mrleebo/prisma-ast

This library uses an abstract syntax tree to parse schema.prisma files into an object in JavaScript. It also allows you to update your Prisma schema files using a Builder object pattern that is fully implemented in TypeScript.

It is similar to @prisma/sdk except that it preserves comments and model attributes. It also doesn't attempt to validate the correctness of the schema at all; the focus is instead on the ability to parse the schema into an object, manipulate it using JavaScript, and re-print the schema back to a file without losing information that isn't captured by other parsers.

It is probable that a future version of @prisma/sdk will render this library obsolete.

Install

npm install @mrleebo/prisma-ast

Examples

Produce a modified schema by building upon an existing schema

produceSchema(source: string, (builder: PrismaSchemaBuilder) => void, printOptions?: PrintOptions): string

produceSchema is the simplest way to interact with prisma-ast; you input your schema source and a producer function to produce modifications to it, and it will output the schema source with your modifications applied.

import { produceSchema } from '@mrleebo/prisma-ast'

const input = `
model User {
  id   Int    @id @default(autoincrement())
  name String @unique
}
`

const output = produceSchema(source, (builder) => {
  builder
    .model("AppSetting")
    .field('key', 'String', [{ name: 'id' }])
    .field('value', 'Json')
})

model User {
  id   Int    @id @default(autoincrement())
  name String @unique
}

model AppSetting {
  key   String @id
  value Json
}

For more information about what the builder can do, check out the PrismaSchemaBuilder class.

PrismaSchemaBuilder

The produceSchema() utility will construct a builder for you, but you can also create your own instance, which may be useful for more interactive use-cases.

import { createPrismaSchemaBuilder } from '@mrleebo/prisma-ast'

const builder = createPrismaSchemaBuilder()

builder.model('User')
  .field('id', 'Int')
  .attribute('id')
  .attribute('default', [{ function: 'autoincrement' }])
  .field('name', 'String')
  .attribute('unique')
  .break()
  .comment("this is a comment")
  .blockAttribute('index', ['name'])

const output = builder.print()

model User {
  id   Int @id @default(autoincrement())
  name String @unique

  // this is a comment
  @@index([name])
}

Re-sort the schema

prisma-ast can sort the schema for you. The default sort order is ['generator', 'datasource', 'model', 'enum'] and will sort objects of the same type alphabetically.

print(options?: { 
  sort: boolean,
  locales?: string | string[],
  sortOrder?: Array<'generator' | 'datasource' | 'model' | 'enum'>
})

You can optionally set your own sort order, or change the locale used by the sort.

// sort with default parameters
builder.print({ sort: true })

// sort with options
builder.print({ 
  sort: true, locales: 'en-US', sortOrder: ['datasource', 'generator', 'model', 'enum']
});

Set a datasource

Since a schema can only have one datasource, calling this command will override the existing datasource if the schema already has one, or create a datasource block if it doesn't.

datasource(provider: string, url: string | { env: string })

You can set a datasource by passing in the provider and url parameters.

builder.datasource('postgresql', { env: 'DATABASE_URL' })

datasource db {
  provider = "postgresql"
  url      = env("DATABASE_URL")
}

Add or update a generator

generator(name: string, provider: string)

If the schema already has a generator with the given name, it will be updated. Otherwise, a new generator will be created.

builder.generator('nexusPrisma', 'nexus-prisma')

generator nexusPrisma {
  provider = "nexus-prisma"
}

Adding additional assignments to generators

assignment(key: string, value: string)

If your generator accepts additional assignments, they can be added by chaining .assignment() calls to your generator.

builder.generator('client', 'prisma-client-js').assignment('output', 'db.js')

generator client {
  provider = "prisma-client-js"
  output = "db.js"
}

Add or update a model

If the model with that name already exists in the schema, it will be selected and any fields that follow will be appended to the model. Otherwise, the model will be created and added to the schema.

builder.model('Project').field('name', 'String')

model Project {
  name String
}

Add a field with an attribute to a model

If the entered model name already exists, that model will be used as the subject for any field and attribute calls that follow.

builder.model('Project').field('projectCode', 'String').attribute('unique')

model Project {
  name        String
  projectCode String @unique
}

Add an index to a model

builder.model('Project').blockAttribute('index', ['name'])

model Project {
  name        String
  projectCode String @unique
  @@index([name])
}

Add an enum

builder.enum('Role', ['USER', 'ADMIN'])

enum Role {
  USER
  ADMIN
}

Additional enumerators can also be added to an existing Enum

builder.enum('Role').break().comment("New role added for feature #12").enumerator('ORGANIZATION')

enum Role {
  USER
  ADMIN

  // New role added for feature #12
  ORGANIZATION
}

Comments and Line breaks are also parsed and can be added to the schema

builder
  .model("Project")
  .break()
  .comment("I wish I could add a color to your rainbow")

model Project {
  name        String
  projectCode String @unique
  @@index([name])

  // I wish I could add a color to your rainbow
}

Underlying utility functions

The produceSchema and createPrismaSchemaBuilder functions are intended to be your interface for interacting with the prisma schema, but you can also get direct access to the AST representation if you need to edit the schema for more advanced usages that aren't covered by the methods above.

Parse a schema.prisma file into an AST object

The shape of the AST is not fully documented, and it is more likely to change than the builder API.

import { getSchema } from '@mrleebo/prisma-ast'

const source = `
model User {
  id   Int    @id @default(autoincrement())
  name String @unique
}
`

const schema = getSchema(source)

Print a schema AST back out as a string

This is what builder.print() calls internally, and is what you'd use to print if you called getSchema().

import { printSchema } from '@mrleebo/prisma-ast'

const source = printSchema(schema)

You can optionally re-sort the schema. The default sort order is ['generator', 'datasource', 'model', 'enum'], and objects with the same type are sorted alphabetically, but the sort order can be overridden.

const source = printSchema(schema, { sort: true, locales: "en-US", sortOrder: ["datasource", "generator", "model", "enum"] })