pglite-typegen

Generates TypeScript types by introspecting a PGlite database through pg_catalog. Plain interfaces by default; Kysely Generated<> output is an opt-in flag, not the default.

Why this approach

PGlite is Postgres compiled to WASM, so its pg_catalog is standard Postgres. There is no SQL parsing and nothing is executed — the tool opens an existing PGlite data dir and asks the catalog what the schema actually is. This captures, with zero guessing: enums (as string-literal unions), domains (resolved to their base type via a recursive CTE), standalone composite types, array columns, and nullability. However the schema got into the dir — any migration tool, raw SQL, DO blocks — is irrelevant, because the catalog reflects the final state regardless.

Usage

# Plain TypeScript interfaces (default)
pglite-typegen ./.pglite --out ./src/db.ts

# Kysely DB interface with Generated<> wrappers
pglite-typegen ./.pglite --out ./src/db.ts --kysely

# Multiple schemas, numeric/bigint as number
pglite-typegen ./.pglite --schemas public,app \
  --out ./src/db.ts --numeric-as-number

With --kysely, columns with a default / identity / generated value are wrapped in Generated<> (so they're optional on insert) and the file imports Generated from kysely. Without it, every column is T or T | null and there is no kysely dependency at all.

The dir must already contain the schema (run your migrations into it beforehand, by whatever means — that's not this tool's job).

Programmatic

import { generate } from "pglite-typegen";
await generate({ dataDir: "./.pglite", outFile: "./src/db.ts" });

generate() also accepts { pglite } (any object with .query), which overrides dataDir and is how the test suite runs without a real PGlite.

Type mapping notes

• int8 / numeric → string by default (avoids 2^53 precision loss). --numeric-as-number overrides.
• json / jsonb → unknown (annotate yourself if you have a shape).
• Unknown base types emit string /* unmapped pg type: <name> */ so they surface in review rather than silently becoming any.
• Non-public schemas: interface name is Schema_TableTable, DB key is "schema.table".

Tests

bun test — validates the model builder and emitter against synthetic pg_catalog rows shaped exactly as the introspection queries return them (enum, domain, composite, array, identity, generated, nullable), covering both the plain default output and the --kysely opt-in. Bun resolves the .ts sources directly, so no build step or loader is needed to run it.