Transform Prisma DMMF (Data Model Meta Format) to JSON Schema v7 for validation and documentation generation

@visulima/prisma-dmmf-transformer

Transform Prisma's internal Data Model Meta Format (DMMF) to JSON Schema v7, enabling schema validation, documentation generation, and integration with JSON Schema tools.

Key Features

Prisma Integration

DMMF Access - Extract Prisma's internal data model structure
Model Transformation - Convert Prisma models to JSON Schema definitions
Enum Support - Transform Prisma enums to JSON Schema enums
Type Mapping - Map Prisma types to JSON Schema types

JSON Schema Generation

v7 Compliance - Generates valid JSON Schema v7 output
Definitions - Creates reusable schema definitions
Properties - Generates properties with type references
Validation - Includes field validation constraints

Configuration Options

Relation Fields - Control scalar field exposure (keepRelationScalarFields)
Required Fields - Include required field constraints (includeRequiredFields)
Original Types - Preserve Prisma type information (persistOriginalType)
Schema ID - Set custom schema identifier (schemaId)

Quick Start

import { PrismaClient } from "@prisma/client";
import { transformDMMF } from "@visulima/prisma-dmmf-transformer";

const prisma = new PrismaClient();

// Get DMMF from Prisma
const dmmf = await (prisma as any)._getDmmf();

// Transform to JSON Schema
const jsonSchema = transformDMMF(dmmf, {
  keepRelationScalarFields: "true",
  includeRequiredFields: "true",
  persistOriginalType: "true",
  schemaId: "https://example.com/schema",
});

console.log(jsonSchema);
// Output: JSON Schema v7 with model definitions

Use Cases

Schema Validation

Validate data against Prisma models using JSON Schema validators:

import { transformDMMF } from "@visulima/prisma-dmmf-transformer";
import Ajv from "ajv";

const dmmf = await (prisma as any)._getDmmf();
const schema = transformDMMF(dmmf, {
  includeRequiredFields: "true",
});

const ajv = new Ajv();
const validate = ajv.compile(schema.definitions.User);

const valid = validate({
  id: 1,
  email: "user@example.com",
  name: "John Doe",
});

if (!valid) {
  console.error("Validation errors:", validate.errors);
}

API Documentation

Generate OpenAPI/Swagger documentation from Prisma models:

import { transformDMMF } from "@visulima/prisma-dmmf-transformer";

const dmmf = await (prisma as any)._getDmmf();
const schema = transformDMMF(dmmf, {
  schemaId: "https://api.example.com/schema",
  persistOriginalType: "true",
});

// Use in OpenAPI spec
const openApiSpec = {
  openapi: "3.0.0",
  components: {
    schemas: schema.definitions,
  },
  paths: {
    "/users": {
      get: {
        responses: {
          200: {
            content: {
              "application/json": {
                schema: { $ref: "#/components/schemas/User" },
              },
            },
          },
        },
      },
    },
  },
};

Custom Generators

Build custom Prisma generators using the transformer:

import { generatorHandler } from "@prisma/generator-helper";
import { transformDMMF } from "@visulima/prisma-dmmf-transformer";

generatorHandler({
  onManifest: () => ({
    defaultOutput: "./generated",
    prettyName: "JSON Schema Generator",
  }),
  onGenerate: async (options) => {
    const schema = transformDMMF(options.dmmf, {
      includeRequiredFields: "true",
    });

    // Write schema to file
    await writeFile(
      "./generated/schema.json",
      JSON.stringify(schema, null, 2)
    );
  },
});