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Reason toolchain packaged for npm.


Supported: Installing via NPM/Yarn, on Mac OS or Linux.


platform install command
macOS yarn global add reason-cli@latest-macos
Linux yarn global add reason-cli@latest-linux
Windows Please see reasonml/

For npm users, use npm install -g reason-cli@latest-macos or @latest-linux instead.

The package's size is rather big. It takes a while to download, especially on slower internet. If npm is stuck and doesn't produce any errors then it's probably just downloading it. This will be fixed in the following releases. Sorry.

The installation requires glibc >=3.4.21. If you're on macOS, you should be good to go. If you're on Ubuntu, reason-cli requires Ubuntu 16.04. Otherwise the postinstall might fail.

If you are having trouble, you can download the tarball to your machine separately, and run npm install path/to/tarball, to install from the local file.

Install your editor plugins

Pick your favorite editor plugin here


Just reinstall over the previously installed package. It's usually a good idea to uninstall the old reason-cli first.

npm uninstall -g reason-cli
npm install -g reason-cli@latest-macos

Included Binaries

When installed with npm install -g, reason-cli places the following tools in your path:

  • ocamlmerlin
  • ocamlmerlin-reason
  • refmt
  • rtop

Releasing (For Maintainers):

Repeat the following for both most recent reason-cli linux and macos circle CI builds that succeed.

  1. Bump the versions/config in package.json to your liking, and make sure to locally run esy install to regenerate any lockfiles. Send a commit with those lockfiles and config changes.
  2. When that diff builds on master, grab the results from the Artifacts tab on the CircleCI build results for the build of the platform you want to release.
  3. Verify the release can be installed: npm remove -g reason-cli && npm install reason-cli.tar.gz
  4. Make sure rtop works.
  5. Uninstall the release you just installed: npm remove -g reason-cli (otherwise npm freaks out).
  6. Extract the release locally: tar -xvf reason-cli.tar.gz.
  7. cd package
  8. Edit the version number in package.json to be 3.3.2-linux or 3.3.2-macos (adjust for the version and platform you downloaded for accordingly).
  9. npm publish

Repeat steps 1-8 for both linux and macos builds.

  1. Update dist tags:
    npm dist-tags add reason-cli@3.3.2-linux latest-linux
    npm dist-tags add reason-cli@3.3.2-macos latest-macos
    (adjust for the version and platform you downloaded for accordingly)

Releasing (without CI):

You can just recreate what the circle CI steps do locally and then perform the steps above.

More Info


  • For failed installs try:

    npm install -g whateverReasonCliReleaseYouTried --ignore-scripts
    cd whereverYourGlobalNpmPackagesAreStored/reason-cli/
    • Does it give any better information about what is failing?
    • Is there a specific log file that it claims the actual error is written into?
  • Did you remember to install using -g?

  • When updating, did you try to uninstall the previous installation?

Each published binary includes the built-in ability to troubleshoot where each binary is resolved to. If something is going wrong with your refmt command, you can see which released binary refmt actually invokes in the release. We use the ----where flag with four - characters because it's unlikely to conflict with any meaningful parameters of binaries like refmt.

refmt ----where

> /path/to/npm-packages/lib/reason-cli/actualInstall/builds/reason/bin/refmt




Globally installable Reason toolchain.







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