Running swc on multiple folders in a monorepo workspace

This repository is a minimal reproduction of a problem I filed in the swc repository: swc-project/swc#8139

In this monorepo there is a single backend project. It consists of 3 "root" folders:

• integration-tests
• generated
• src

The goal is to transpile all 3 folders (even though integration-tests is not actually necessary for the app to run) with a single command.

When you run "compile:tsc" (tsc -b) script in the package/backend workspace, it produces the .js output in an analogous structure of the package/backend folder, nested inside dist:

$ tree -L 2 dist
dist
├── generated
│   └── some-api
├── integration-tests
│   ├── one.d.ts
│   └── one.js
├── src
│   ├── main.d.ts
│   ├── main.js
│   ├── service-A
│   └── service-B
└── tsconfig.tsbuildinfo

I want to achieve the same result with swc. But it turns out that swc . -d dist does not work at all. I tried to come up with various different ways that could work. I've listed them below.

Different approaches

• "compile:swc:inner:relative" (swc . -d dist)

  ❌ This is the most natural way of running the command, but it does not generate any output.

• "compile:swc:outer:relative" (cd ..; swc backend -d backend/dist --config-file backend/.swcrc)

  ✅ Generates correct output.

• "compile:swc:outer:absolute" (cd ..; swc $PWD -d $PWD/dist --config-file $PWD/.swcrc)

  ✅ Generates correct output.

• "compile:swc:inner:absolute" (swc $PWD -d $PWD/dist --config-file $PWD/.swcrc)

  ❌ Generates a malformed (flattened) directory structure.

  $ tree -L 2 dist
  
  dist
  ├── main.js
  ├── main.js.map
  ├── one.js
  ├── one.js.map
  ├── service-A
  │   ├── a.js
  │   └── a.js.map
  ├── service-B
  │   ├── b.js
  │   └── b.js.map
  └── some-api
    ├── api.js
    └── api.js.map
  
  3 directories, 10 files
  

• "compile:swc:inner:separate" (swc src -d dist/src & swc generated -d dist/generated & swc integration-tests -d dist/integration-tests)

  ✅ Generates correct output.

The "outer" commands look like a hack. When working in a monorepo like this one, it is required to use the top-level swc packages, cause yarn will not let you run backend's copy of swc from an outer directory. This means that you cannot use the devDependency of a package to build it, you need to rely on external tools, which is not as portable as I'd like it to be.

The "inner" commands do not work correctly. The relative version is what I'd suppose to be the correct usage of the CLI, but it does not produce any output. What's also weird is that providing the same absolute paths as for the "outer absolute" script generates a different output when run inside the workspace folder.

Running 3 separate commands for each of the root folders provides a correct output, but it requires listing the folders manually. You cannot combine such script with a flag like --watch by appending the flag, because it will be only applied to the last command.