[Feature Request] Add schema generation API `generate`

[good-jinu]

Thank you for building and maintaining unadapter! It's an amazing tool that really simplifies managing dynamic database adapters.

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Old request

Feature Request

I would like to request a schema generation feature for unadapter.

While unadapter currently provides an adapter-agnostic way to handle live database migrations via getMigrations(), it lacks a standalone code/schema generation mechanism. In comparison, better-auth (which unadapter's architecture is based on) provides a built-in CLI that allows users to generate the required database schemas or migration files based on configured tables and plugins:

npx auth@latest generate

I'm a Library author building on top of unadapter and and try to expose package's own CLI. A very common command is a generate step that writes out a schema file:

npx my-lib generate

This kind of command needs to produce schema output from the schema definition. At this point, there is no database to connect to

Summary

unadapter can run and compile migrations through getMigrations(), but every path through it requires a live database connection. There is currently no public API to turn a TablesSchema into a schema string (SQL DDL, and Prisma/Drizzle) offline, without connecting to a database.

[productdevbook]

Thank you :) Welcome pr ! Would you like to try it?

[good-jinu]

Thanks @productdevbook ! I'd love to take this on.
Before I start, should the CLI live in the same package or a separate unadapter/cli subpath?
IMO, I'd like to keep it in the same package for now and extract it later if needed.

[productdevbook]

I don't want to limit your ideas. You should do whatever you want. We'll review it later.

[good-jinu]

I’ve updated the issue description because the original version didn’t fully capture my intention. I rewrote it based on the real problem I’m facing as a open source author.
After clarifying the background, I realized that instead of adding a CLI to unadapter itself, what’s actually needed is a public generate API

Here i opened #14