@greffon/ts-transformer

The TypeScript-compiler transformer of Greffon, expression trees for TypeScript. For projects that compile with tsc (or tsc -b) and no bundler, it does during compiler emit what @greffon/vite does in a bundler: validate query lambdas against the expression subset and reify each into __expr({...}), keeping the original function as compiled.

Detection and capture live in @greffon/transform, shared with the Vite plugin, so both paths agree on what is legal. typescript is a peer dependency (>=5); the compiler is the host, brought by you.

Install

npm install -D @greffon/ts-transformer ts-patch

Usage

Stock tsc runs no custom emit transformers; ts-patch fills that gap. Register the transformer in tsconfig.json:

{
  "compilerOptions": {
    "module": "nodenext",
    "plugins": [{ "transform": "@greffon/ts-transformer" }]
  }
}

Then compile with npx tspc (or run ts-patch install once, then tsc). Options go on the same plugin entry.

Driving the compiler API yourself, pass the factory to program.emit as a before transformer:

import ts from "typescript";
import { createTransformerFactory } from "@greffon/ts-transformer";

const program = ts.createProgram(fileNames, compilerOptions);
program.emit(undefined, undefined, undefined, false, {
  before: [createTransformerFactory(program, { packages: ["@greffon/query"] })],
});

Pass the program so cross-file contexts resolve; without it, only expr() wrappers and same-module contexts reify.

Limits

• ES-module output only: set module to esnext or nodenext. CommonJS emit is refused (unbound host import).
• It runs during emit, so .d.ts output and type checking are unaffected.
• An emitter that skips the TypeScript program (esbuild, swc, Babel) never runs it. Use the Vite plugin there.
• Source maps are coarser than the Vite plugin's; prefer the bundler plugin when you need exact maps.

Docs

• Compiling with tsc — setup and the full options table
• Error reference

License

MIT