Kysely schema generator

A very quickly hacked-together schema generator for Kysely which (currently) only supports MySQL.

Installation

With your package manager of choice install:

npm install --save @deanc/kysely-schema-generator
yarn add @deanc/kysely-schema-generator
pnpm add @deanc/kysely-schema-generator

Configuration

Either in your project root or somewhere else create a .env file with a DATABASE_URL environmental variable:

DATABASE_URL='mysql://user:password@host:3306/databaseName'

Usage

Option 1 (.env in project root and run)

kysely-schema-generator

Option 2 (.env somewhere else)

kysely-schema-generator -p /path/to/.env

Note if command can't be found you might need to use your package manager to run it (e.g. pnpm exec kysely-schema-generator)

Option 3 (write output to a file)

kysely-schema-generator -o ./kysely-db.ts

Option 4 (override database/schema name)

kysely-schema-generator -d my_database

Option 5 (include or exclude specific tables)

kysely-schema-generator -t users,orders
kysely-schema-generator -x audit_logs,temp_records

Option 6 (disable formatting)

kysely-schema-generator --no-format

Option 7 (map TINYINT(1) to boolean)

kysely-schema-generator --tinyint1-as-boolean

Options

-p, --path-env <path>           path to .env file
-o, --output <path>             write output to a file
-d, --database <name>           override database/schema name
-t, --tables <list>             comma-separated list of tables to include
-x, --exclude-tables <list>     comma-separated list of tables to exclude
    --no-format                 disable output formatting
    --tinyint1-as-boolean       map TINYINT(1) columns to boolean
-h, --help                      display help

Example Output

Given a users table:

CREATE TABLE users (
  id INT NOT NULL AUTO_INCREMENT,
  email VARCHAR(255) NOT NULL,
  status ENUM('active','inactive') NOT NULL,
  created_at TIMESTAMP NULL
)

The generator outputs:

import { Generated, Insertable, Selectable, Updateable } from 'kysely'

interface UsersTable {
  id: Generated<number>
  email: string
  status: 'active' | 'inactive'
  created_at: string | null
}
export type Users = Selectable<UsersTable>
export type NewUsers = Insertable<UsersTable>
export type UsersUpdate = Updateable<UsersTable>

export interface DB {
  users: Users
}

Integration Test (MySQL)

This test uses Testcontainers and will spin up MySQL automatically (Docker must be running).

pnpm run test:integration

Troubleshooting

• No valid DATABASE_URL process.env found: ensure your .env file is in the path provided via --path-env, or in the project root, and contains a valid DATABASE_URL.
• Testcontainers runtime unavailable: make sure Docker is running and accessible from your terminal.
• Permissions errors: the MySQL user in the URL needs access to information_schema and the target database.

Limitations

• MySQL only (no Postgres/SQLite support yet).
• Some MySQL types may still be missing or mapped conservatively (e.g. JSON uses unknown).
• Numeric precision/scale is not currently used to refine type output.

Development

pnpm install
pnpm test
pnpm run test:integration
pnpm run lint

Todo

(Contributions very welcome)

• Ensure all MySQL field types are mapped correctly
• Add support for other database engines (Postgres, SQLite at least)
• Add test coverage
• (Maybe) offer option to write to disk instead of relying on user to capture