@datocms/cma-schema-types-generator

Generate TypeScript type definitions from a DatoCMS project schema.

Produces ItemTypeDefinition-based types (one per model/block) plus AnyBlock / AnyModel / AnyBlockOrModel union types, ready to be used with @datocms/cma-client for type-safe content management and migration scripts.

Installation

npm install @datocms/cma-schema-types-generator

@datocms/cma-client is a peer dependency.

Usage

import { buildClient } from '@datocms/cma-client';
import { generateSchemaTypes } from '@datocms/cma-schema-types-generator';

const client = buildClient({ apiToken: process.env.DATOCMS_API_TOKEN! });
const code = await generateSchemaTypes(client);

code is a string containing prettier-formatted TypeScript, ready to be written to disk:

import { writeFile } from 'node:fs/promises';

await writeFile('src/generated/schema.ts', code);

Example output

import type { ItemTypeDefinition } from '@datocms/cma-client';

type EnvironmentSettings = {
  locales: 'en' | 'it';
};

export type BlogPost = ItemTypeDefinition<
  EnvironmentSettings,
  '12345',
  {
    title: { type: 'string'; localized: true };
    content: { type: 'rich_text'; blocks: Hero };
  }
>;
export const BlogPost = {
  ID: '12345',
  REF: { type: 'item_type', id: '12345' },
} as const;

export type Hero = ItemTypeDefinition<EnvironmentSettings, '67890', { /* … */ }>;
export const Hero = {
  ID: '67890',
  REF: { type: 'item_type', id: '67890' },
} as const;

export type AnyBlock = Hero;
export type AnyModel = BlogPost;
export type AnyBlockOrModel = AnyBlock | AnyModel;

Type-and-value declaration merging

Each item type is emitted twice: once as a TypeScript type (the ItemTypeDefinition<…> alias) and once as an export const carrying its runtime metadata. TypeScript merges the two — Schema.BlogPost resolves both as a type and as a value, depending on the position it's used in.

The runtime const exposes two fields:

• ID — the bare item type id (e.g. '12345'), typed as a string literal so it can be used for narrowing.
• REF — the JSON:API resource identifier object { type: 'item_type', id: '<sameId>' }, ready to be passed wherever the API expects an item type reference.

This lets call sites stay free of hardcoded string ids:

import { buildClient } from '@datocms/cma-client';
import * as Schema from './generated/schema';

const client = buildClient({ apiToken: process.env.DATOCMS_API_TOKEN! });

await client.items.create<Schema.LandingPage>({
  item_type: Schema.LandingPage.REF,
  title: 'Hello world',
});

if (block.__itemTypeId === Schema.HeroBlock.ID) {
  // narrowed to Schema.HeroBlock
}

Options

Both entry points accept an optional SchemaTypesGeneratorOptions object:

• itemTypesFilter — comma-separated list of model api keys to include. Block dependencies referenced by the kept models (through rich_text, structured_text, single_block) are pulled in automatically. Unknown api keys are ignored.
• format — formats the output with Prettier. Defaults to true. Prettier runs in a worker thread whose memory does not go back to the main process: on a project with thousands of fields this adds hundreds of megabytes to the peak memory use. Set it to false when the code goes to a compiler and not to a person. The TypeScript printer already emits indented, multi-line code; only the quote style and the line breaks are different.

Migration variant

generateSchemaTypesForMigration produces the same declarations without the import type { ItemTypeDefinition } line — meant to be inlined directly inside a migration script that already has access to the type.

import { generateSchemaTypesForMigration } from '@datocms/cma-schema-types-generator';

const inline = await generateSchemaTypesForMigration(client, {
  itemTypesFilter: 'blog_post,author',
});