Path aliases

If your tsconfig.json uses compilerOptions.paths (e.g. @/* → ./src/*), the emit will contain those alias paths verbatim, and they won’t resolve at runtime. @ttsc/paths rewrites them into relative imports during compile.

The problem


// src/main.ts (source)
import { value } from "@lib/value";

After a plain ttsc build:


// dist/main.js (broken)
import { value } from "@lib/value"; // ← Node can't resolve this

The fix


npm install -D @ttsc/paths


// tsconfig.json
{
  "compilerOptions": {
    "rootDir": "src",
    "outDir": "dist",
    "paths": {
      "@/*": ["./src/*"],
      "@lib/*": ["./src/modules/*"]
    },
    "plugins": [{ "transform": "@ttsc/paths" }]
  }
}

Now the emit is:


// dist/main.js
import { value } from "./modules/value.js";

What it does and doesn’t do

Reads the same compilerOptions.paths, rootDir, and outDir that ttsc already uses.
Rewrites JavaScript-family emit (.js, .mjs, .cjs, .jsx) and .d.ts declarations.
Resolves extensionless path targets against .ts, .tsx, .mts, .cts, then .js, .jsx, .mjs, and .cjs source files.
No separate plugin config.
Only rewrites specifiers that match compilerOptions.paths; relative, absolute, and non-matching package specifiers are left alone.
Uses TypeScript-Go’s emitted runtime suffix for matched targets (.js, .mjs, .cjs, or .jsx depending on the source file and jsx mode).
Does not change source files: only the emit.

Common alternatives (and why this is simpler)

tsc-alias: post-build script. Works, but it’s a second pass. @ttsc/paths runs inside the compile.
Path remapping at runtime via tsconfig-paths/register: adds runtime cost and a startup step. @ttsc/paths produces normal relative imports.
Custom bundler config: if a bundler owns your build, that’s fine. @ttsc/paths is for projects that ship as plain Node packages.

Inspired by

typescript-transform-paths. Same goal, different compiler.