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, rescript.json.

Options

See rescript help:

❯ rescript help
Usage: rescript <options> <subcommand>

`rescript` is equivalent to `rescript build`

Options:
  -v, -version  display version number
  -h, -help     display help

Subcommands:
  build
  clean
  format
  convert
  dump
  help

Run `rescript <subcommand> -h` for subcommand help. Examples:
  rescript build -h
  rescript format -h

Build Project

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

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

SH
rescript

Which is an alias for rescript build.

To keep a build watcher, run:

SH
rescript -w

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

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

For monorepo setup in ReScript 12+, see Setting up a monorepo.

Clean Project

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

SH
rescript clean

Compile with stricter errors in CI

Since 11.1

You may want to compile your project with stricter rules for production, than when developing. With the -warn-error build flag, this can easily be done, for instance in a continuous integration script. E.g.:

SH
rescript -warn-error +110

Here, warning number 110, which is triggered when a %todo has been found, gets promoted to an error. The full list of warning numbers can be found here.