CompilerConfigurationSpec.md

ReScript build configuration

This document lists configuration fields recognized by Rewatch and whether their behavior is implemented. The public schema is maintained in the ReScript manual. Compatibility fields can remain implemented here after they stop being recommended for new projects.

Parameter	JSON type	Remark	Implemented?
name	string		[x]
namespace	boolean		[x]
namespace	string		[x]
sources	string		[x]
sources	array of string		[x]
sources	Source		[x]
sources	array of Source		[x]
ignored-dirs	array of string		[_]
dependencies	array of string		[x]
dependencies	array of Dependency	See Features.md. rewatch extension.	[x]
dev-dependencies	array of string		[x]
dev-dependencies	array of Dependency	See Features.md. rewatch extension.	[x]
features	map of string to array	See Features.md. rewatch extension.	[x]
generators	array of Rule-Generator		[_]
cut-generators	boolean		[_]
jsx	JSX		[x]
gentypeconfig	Gentype		[x]
compiler-flags	array of string		[x]
warnings	Warnings		[x]
ppx-flags	array of string		[x]
pp-flags	array of string		[_]
js-post-build	Js-Post-Build	Path respects in-source setting; stdout/stderr are logged	[x]
package-specs	array of Module-Format		[_]
package-specs	array of Package-Spec		[x]
entries	array of Target-Item		[_]
bs-external-includes	array of string		[_]
suffix	Suffix		[x]
reanalyze	Reanalyze	Reanalyze config; ignored by rewatch	[x]
experimental-features	ExperimentalFeatures		[x]
editor	object	VS Code tooling only; ignored by rewatch	[x]

Source

Parameter	JSON type	Remark	Implemented?
dir	string		[x]
type	"dev"		[x]
feature	string	See Features.md. rewatch extension.	[x]
files	array of string		[_]
files	File-Object		[_]
generators	array of Build-Generator		[_]
public	"all"		[_]
public	array of string		[_]
resources	array of string		[_]
subdirs	boolean		[x]
subdirs	string		[_]
subdirs	array of string		[x]
subdirs	Source		[_]
subdirs	array of Source		[x]
group	string		[_]
group	Group		[_]
internal-depends	array of string		[_]

File-Object

Parameter	JSON type	Remark	Implemented?
slow-re	string		[_]
excludes	array of string		[_]

Build-Generator

Parameter	JSON type	Remark	Implemented?
name	string		[_]
edge	array of string		[_]

Rule-Generator

Parameter	JSON type	Remark	Implemented?
name	string		[_]
command	string		[_]

JSX

Parameter	JSON type	Remark	Implemented?
version	JSX-Version		[x]
module	"react"		[x]
mode	JSX-Mode		[x]
v3-dependencies	array of string		[x]

JSX-Version

enum: 3 | 4

JSX-Mode

enum: "classic" | "automatic"

Gentype

Parameter	JSON type	Remark	Implemented?
path	string		[_]

Reanalyze

Parameter	JSON type	Remark	Implemented?
analysis	array of Reanalyze-Analysis		[_]
suppress	array of string		[_]
unsuppress	array of string		[_]
transitive	boolean		[_]

Reanalyze-Analysis

enum: | "dce" | "exception" | "termination"

ExperimentalFeatures

An object of feature flags to enable experimental compiler behavior. Only supported by Rewatch.

• Keys: feature identifiers (PascalCase)
• Values: boolean (true to enable)

Currently supported features:

• LetUnwrap: Enable let? syntax.

Warnings

Parameter	JSON type	Remark	Implemented?
number	string		[x]
error	boolean		[x]
error	string		[x]

Js-Post-Build

Parameter	JSON type	Remark	Implemented?
cmd	string	Receives absolute path to JS file	[x]

The path passed to the command respects the in-source setting:

• in-source: true → path next to the source file (e.g., src/Foo.js)
• in-source: false → path in lib/<module>/ directory (e.g., lib/es6/src/Foo.mjs)

The command runs with the same working directory as the rewatch process (typically the project root).

stdout and stderr from the command are logged.

Package-Spec

Parameter	JSON type	Remark	Implemented?
module	Module-Format		[_]
in-source	boolean		[x]
suffix	Suffix		[_]

Module-Format

enum: "esmodule" | "commonjs"

default: "esmodule"

Suffix

enum: ".js" | ".mjs" | ".cjs" | ".bs.js" | ".bs.mjs" | ".bs.cjs"

Target-Item

Not really usable by ReScript, likely to be removed.

Parameter	JSON type	Remark	Implemented?
kind	Target-Item-Kind		[_]
main	string		[_]

Target-Item-Kind

enum: "native" | "bytecode" | "js"

Group

What is this even for? The spec says it is not even implemented in ReScript. Likely to be removed.

Parameter	JSON type	Remark	Implemented?
name	string		[_]
hierarchy	boolean		[_]