Hi!

I was just testing bun with rescript 12 RC in a monorepo setup, did the workspaces in package.json, listed the package dependencies in the root rescript.json and got this error when building:

We could not build package tree reading dependency 'starter', at path '<redacted>'. Error: try_package_path: upward traversal did not find 'starter' starting at '<redacted>'

Just wanted to share, by default bun uses isolated installs like pnpm I believe, and it wasn’t creating symlinks to the workspace packages in node_modules, which rescript 12 (rewatch) needs.

To solve this in an automated way (no manual symlinks) and without changing the bun linker to hoisted, I decided to add the packages to the dependencies in the root package.json like so:

  "dependencies": {
    "starter": "workspace:*"
  },

Which then when bun install it will make a symlink from the root node_modules/starter to the packages/starter folder. Then rescript works just fine.

Just sharing in case anyone else hits this issue or someone has other solutions. Here is a summary of how it looks like:

ReScript Monorepo Setup with Bun Workspaces

Directory Structure

.
├── bun.lock
├── package.json
├── rescript.json
└── packages
    └── starter
        ├── package.json
        ├── rescript.json
        └── src
            ├── Demo.res
            └── Demo.res.mjs

Root package.json

{
  "name": "monorepo",
  "private": true,
  "workspaces": {
    "packages": [
      "packages/*"
    ],
    "catalog": {
      "rescript": "^12.0.0-rc.3"
    }
  },
  "scripts": {
    "build": "rescript build",
    "clean": "rescript clean",
    "dev": "rescript watch",
    "format": "rescript format -all",
  },
  "dependencies": {
    "@monorepo/starter": "workspace:*"
  },
  "devDependencies": {
    "rescript": "catalog:"
  },
}

Root rescript.json

{
  "name": "monorepo",
  "sources": [],
  "package-specs": {
    "module": "esmodule",
    "in-source": true
  },
  "suffix": ".res.mjs",
  "dependencies": ["@monorepo/starter"],
  "compiler-flags": []
}

Package package.json (packages/starter/package.json)

{
  "name": "@monorepo/starter",
  "version": "0.0.0",
  "description": "ReScript starter package",
  "main": "src/Demo.res.mjs"
}

Package rescript.json (packages/starter/rescript.json)

{
  "name": "@scope/starter",
  "sources": {
    "dir": "src",
    "subdirs": true
  },
  "package-specs": {
    "module": "esmodule",
    "in-source": true
  },
  "suffix": ".res.mjs",
  "dependencies": [],
  "compiler-flags": []
}

Adding New Packages

1. Create directory in packages/new-package/
2. Add to root package.json dependencies: "@monorepo/new-package": "workspace:*"
3. Add to root rescript.json dependencies: ["@monorepo/new-package"]
4. Run bun install to create symlinks

And a couple of links that helped me out:

• Setting up a monorepo | ReScript Language Manual
• Isolated installs - Bun

Let me know how y’all do it!