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Convert your Reason project from Reason 2 to 3

What is Reason 2/3?

See the announcement and the changelog guide.

How do I upgrade my project?

Before you start

Converting your code to to the new syntax is done by running the upgradeSyntaxFrom2To3 converter on your project's Reason code. Make sure that your project is syntactically valid in Reason 2. Invalid code will fail to convert.

Convert your code

Do this at the root of your project:

npm install -g upgrade-reason-syntax
npm install --save-dev bs-platform@2.2.2
upgradeSyntaxFrom2To3 mySource/*

Make sure you did install bs-platform 2.2.2. Sometimes your lockfile might have locked it to 1.x.x. 2.2.2 is also the last version to support Reason syntax 2.

The script accepts a list of files/globs to convert. Pass as many as you want. It'll intelligently skip over any file that's not Reason.

After you're done converting your projects:

  • Remove the backup files at mySource/*.backup
  • Add "refmt": 3 to your bsconfig.json to make BuckleScript use the new syntax.
  • Feel free to uninstall this library!

If you're on native, this is also your workflow. (So you'll need node.js).

How does it work?

It's a simple node.js script that takes the old refmt and the new refmt3 from your project's BuckleScript 2.0.0's source at node_modules/bs-platform, and then:

  • Iterates over all your relevant files, making a backup copy
  • Turns your Reason files into an AST (abstract syntax tree) using refmt
  • Turns the ASTs into the new syntax using refmt3 and writes them back

That's it! Enjoy =)


Yeah. It upgrades your Reason syntax from version 2 to 3






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