Prisma Typescript Interfaces Generator

prisma-generator-typescript-interfaces - A Prisma generator which creates zero-dependency Typescript interfaces from Prisma schema.

Motivation

While Prisma client's generated types are sufficient for most use cases, there are some some scenarios where using them is not convenient or possible, due to the fact that they rely on both the @prisma/client package and on the client generated from your Prisma schema. That is where this generator comes into play. It generates a zero-dependency Typescript file containing type definitions for all your models. Zero-dependency in this case means that the file does not import any other packages, and can be used standalone in any Typescript app. By default the definitions are type compatible with the Prisma client types, however this can be customized via the options, see below for more info.

As example of why this is useful, say you have an API which uses Prisma and responds with models from your DB, and you want to create a DTO package with Typescript definitions for all the data your API returns. You wouldn't really want to include your entire generated Prisma client in that package, and you don't want to require users to install @prisma/client just to use your DTO. So instead, you can use this generator to create a zero-dependency Typescript file containing definitions for all your models, and then use that in your DTO package.

Usage

To use this generator, first install the package:

npm install --save-dev prisma-generator-typescript-interfaces

Next add the generator to your Prisma schema:

generator typescriptInterfaces {
  provider = "prisma-generator-typescript-interfaces"
}

And finally generate your Prisma schema:

npx prisma generate

By default that will output the Typescript interface definitions to a file called interfaces.ts in your prisma folder, this can be changed by specifying the output option. As mentioned above, by default the generated types will be type compatible with the Prisma client types. If you instead want to generate types matching the JSON.stringify-ed versions of your models, you will need to change some of the options, like so:

generator typescriptInterfaces {
  provider    = "prisma-generator-typescript-interfaces"
  dateType    = "string"
  bigIntType  = "string"
  decimalType = "string"
  bytesType   = "BufferObject"
}

Note that bigint types don't have a default toJSON method, so the above assumes that you are converting them to strings somewhere along the line.

Options

Option	Type	Default	Description
output	string	"interfaces.ts"	The output location for the generated Typescript interfaces.
enumPrefix	string	""	Prefix to add to enum types.
enumSuffix	string	""	Suffix to add to enum types.
modelPrefix	string	""	Prefix to add to model types.
modelSuffix	string	""	Suffix to add to model types.
typePrefix	string	""	Prefix to add to type types (mongodb only).
typeSuffix	string	""	Suffix to add to type types (mongodb only).
headerComment	string	"This file was auto-generated by prisma-generator-typescript-interfaces"	Sets the header comment added to the top of the generated file. Set this to an empty string to disable the header comment. Supports multiple lines with "\n".
modelType	"interface" | "type"	"interface"	Controls how model definitions are generated. "interface" will create Typescript interfaces, "type" will create Typescript types. If using mongodb, this also affects type definitions.
enumType	"stringUnion" | "enum" | "both"	"stringUnion"	Controls how enums are generated. "enum" will create Typescript enums, "stringUnion" will create union types with all the enum values. and "both" will do both.
dateType	"Date" | "string" | "number"	"Date"	The type to use for DateTime model fields.
bigIntType	"bigint" | "string" | "number"	"bigint"	The type to use for BigInt model fields.
decimalType	"Decimal" | "string" | "number"	"Decimal"	The type to use for Decimal model fields. The Decimal type here is just an interface with a getValue() function. You will need to cast to an actual Decimal type if you want to use other methods.
bytesType	"Buffer" | "BufferObject" | "string" | "number[]"	"Buffer"	The type to use for Bytes model fields. BufferObject is a type definition which matches the output of Buffer.toJSON(), which is called when running JSON.stringify() on a Buffer.
optionalRelations	boolean	true	Controls whether model relation fields are optional. If true, all model relation fields will use ?: in the field definition.
omitRelations	boolean	false	Controls whether model relation fields are omitted. If true, model definitions will not include their relations.
prettier	boolean	false	Formats the output using Prettier. Setting this to true requires that the prettier package is available.

Example

Here is an example of a configuration which generates two separate outputs, interfaces.ts with types compatible with the Prisma client types, and a second json-interfaces.ts file with types matching the output of JSON.stringify when run on the models. Both files are output to the src/dto folder (which will be created if it doesn't exist) and are formatted using Prettier. The models in json-interfaces.ts also get a Json suffix attached to them.

Input

prisma/schema.prisma

datasource db {
  provider = "postgresql"
  url      = "postgresql://postgres:postgres@localhost:5432/example?schema=public"
}

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

generator typescriptInterfaces {
  provider = "prisma-generator-typescript-interfaces"
  output = "../src/dto/interfaces.ts"
  prettier = true
}

generator typescriptInterfacesJson {
  provider = "prisma-generator-typescript-interfaces"
  output = "../src/dto/json-interfaces.ts"
  modelSuffix = "Json"
  dateType = "string"
  bigIntType = "string"
  decimalType = "string"
  bytesType = "BufferObject"
  prettier = true
}

enum Fruits {
  Apple
  Banana
  Orange
  Pear
}

model RelationA {
  id Int @id
  Data Data[]
}

model RelationB {
  id Int @id
  dataId Int @unique
  data Data @relation(fields: [dataId], references: [id])
}

model RelationC {
  id Int @id
  dataId Int
  data Data @relation(fields: [dataId], references: [id])
}

model Data {
  id Int @id
  stringField String
  booleanField Boolean
  intField Int
  bigIntField BigInt
  floatField Float
  decimalField Decimal
  dateField DateTime
  jsonField Json
  bytesField Bytes
  enumField Fruits
  relationId Int
  relationField RelationA @relation(fields: [relationId], references: [id])

  optionalStringField String?
  optionalBooleanField Boolean?
  optionalIntField Int?
  optionalBigIntField BigInt?
  optionalFloatField Float?
  optionalDecimalField Decimal?
  optionalDateField DateTime?
  optionalJsonField Json?
  optionalBytesField Bytes?
  optionalEnumField Fruits?
  optionalRelationField RelationB?

  stringArrayField String[]
  booleanArrayField Boolean[]
  intArrayField Int[]
  bigIntArrayField BigInt[]
  floatArrayField Float[]
  decimalArrayField Decimal[]
  dateArrayField DateTime[]
  jsonArrayField Json[]
  bytesArrayField Bytes[]
  enumArrayField Fruits[]
  relationArrayField RelationC[]
}

Output

src/dto/interfaces.ts

// This file was auto-generated by prisma-generator-typescript-interfaces

export type Fruits = "Apple" | "Banana" | "Orange" | "Pear";

export interface RelationA {
  id: number;
  Data?: Data[];
}

export interface RelationB {
  id: number;
  dataId: number;
  data?: Data;
}

export interface RelationC {
  id: number;
  dataId: number;
  data?: Data;
}

export interface Data {
  id: number;
  stringField: string;
  booleanField: boolean;
  intField: number;
  bigIntField: bigint;
  floatField: number;
  decimalField: Decimal;
  dateField: Date;
  jsonField: JsonValue;
  bytesField: Buffer;
  enumField: Fruits;
  relationId: number;
  relationField?: RelationA;
  optionalStringField: string | null;
  optionalBooleanField: boolean | null;
  optionalIntField: number | null;
  optionalBigIntField: bigint | null;
  optionalFloatField: number | null;
  optionalDecimalField: Decimal | null;
  optionalDateField: Date | null;
  optionalJsonField: JsonValue | null;
  optionalBytesField: Buffer | null;
  optionalEnumField: Fruits | null;
  optionalRelationField?: RelationB | null;
  stringArrayField: string[];
  booleanArrayField: boolean[];
  intArrayField: number[];
  bigIntArrayField: bigint[];
  floatArrayField: number[];
  decimalArrayField: Decimal[];
  dateArrayField: Date[];
  jsonArrayField: JsonValue[];
  bytesArrayField: Buffer[];
  enumArrayField: Fruits[];
  relationArrayField?: RelationC[];
}

type Decimal = { valueOf(): string };

type JsonValue =
  | string
  | number
  | boolean
  | { [key in string]?: JsonValue }
  | Array<JsonValue>
  | null;

src/dto/json-interfaces.ts

// This file was auto-generated by prisma-generator-typescript-interfaces

export type Fruits = "Apple" | "Banana" | "Orange" | "Pear";

export interface RelationAJson {
  id: number;
  Data?: DataJson[];
}

export interface RelationBJson {
  id: number;
  dataId: number;
  data?: DataJson;
}

export interface RelationCJson {
  id: number;
  dataId: number;
  data?: DataJson;
}

export interface DataJson {
  id: number;
  stringField: string;
  booleanField: boolean;
  intField: number;
  bigIntField: string;
  floatField: number;
  decimalField: string;
  dateField: string;
  jsonField: JsonValue;
  bytesField: BufferObject;
  enumField: Fruits;
  relationId: number;
  relationField?: RelationAJson;
  optionalStringField: string | null;
  optionalBooleanField: boolean | null;
  optionalIntField: number | null;
  optionalBigIntField: string | null;
  optionalFloatField: number | null;
  optionalDecimalField: string | null;
  optionalDateField: string | null;
  optionalJsonField: JsonValue | null;
  optionalBytesField: BufferObject | null;
  optionalEnumField: Fruits | null;
  optionalRelationField?: RelationBJson | null;
  stringArrayField: string[];
  booleanArrayField: boolean[];
  intArrayField: number[];
  bigIntArrayField: string[];
  floatArrayField: number[];
  decimalArrayField: string[];
  dateArrayField: string[];
  jsonArrayField: JsonValue[];
  bytesArrayField: BufferObject[];
  enumArrayField: Fruits[];
  relationArrayField?: RelationCJson[];
}

type JsonValue =
  | string
  | number
  | boolean
  | { [key in string]?: JsonValue }
  | Array<JsonValue>
  | null;

type BufferObject = { type: "Buffer"; data: number[] };

Issues

Please report any issues to the issues page. I am actively using this package, so I'll try my best to address any issues that are reported. Alternatively, feel free to submit a PR.

Developing

All the code for this generator is contained within the generator.ts file. You can build the generator by running npm install then npm run build.

Tests

You can run tests with npm run test. Tests are run using a custom script, see test.ts for details. You can add new tests by placing a Prisma schema and the expected output in a folder under the tests directory, you may want to look at the tests/options-behavior test as an example.

You can run specific tests by passing them as arguments to the test command:

npm run test -- options-behavior validation-errors

When a test fails, you can see the generated output in the __TEST_TMP__ folder inside that test's directory. Compare this with the expected output to see why it failed.

Please ensure all tests are passing and that the code is properly linted (npm run lint) before submitting a PR, thanks!