Build System Overview

ReScript comes with a build system, rescript, that's fast, lean and used as the authoritative build system of the community.

Every ReScript project needs a build description file, bsconfig.json.


See rescript -help:

❯ rescript -help Available flags -v, -version display version number -h, -help display help Subcommands: build clean format convert help Run rescript subcommand -h for more details, For example: rescript build -h rescript format -h The default `rescript` is equivalent to `rescript build` subcommand

Build Project

Each build will create build artifacts from your project's source files.

To build a project (including its dependencies / pinned-dependencies), run:


Which is an alias for rescript build.

To keep a build watcher, run:

rescript build -w

Any new file change will be picked up and the build will re-run.

Note: third-party libraries (in node_modules, or via pinned-dependencies) aren't watched, as doing so may exceed the node.js watcher count limit.

Note 2: In case you want to set up a project in a JS-monorepo-esque approach (npm and yarn workspaces) where changes in your sub packages should be noticed by the build, you will need to define pinned dependencies in your main project's bsconfig.json. More details here.

Clean Project

If you ever get into a stale build for edge-case reasons, use:

rescript clean

This will clean your own project's build artifacts. To also clean the dependencies' artifacts:

rescript clean -with-deps