Purpose

The idea is to ship the r.js distribution with the espree parser instead of esprima which only supports up to ECMA2019.

Espree

Espree is a fork of Esprima, created by the ESLint team. It is designed to be fully compatible with Esprima's API and it is used as the default parser for ESLint.

Given r.js is a standalone script, we need to bundle espree with all of its dependencies so it can be added to the r.js build files, and ultimately to the r.js distro. Hence, we've added a commonjs version of espree, but wrapped as a requirejs module to r.js build folder.

This file is generated by cloning the espree repo and doing the following steps:

Install additional dev dependencies

npm install
npm install -D rollup-plugin-internal
npm install -D @rollup/plugin-node-resolve

Update the rollup configuration

The repo's rollup.config.js file expects the dependencies to be loaded via require, but we need to bundle them with the espree code. Update the config file as follows:

import commonjs from "@rollup/plugin-commonjs";
import resolve from "@rollup/plugin-node-resolve";
import json from "@rollup/plugin-json";
import internal from "rollup-plugin-internal";

export default {
    input: "espree.js",
    external: ["acorn", "acorn-jsx", "eslint-visitor-keys"],
    treeshake: false,
    output: {
        file: "dist/espree.cjs",
        format: "cjs"
    },
    plugins: [commonjs(), resolve(), json(), internal(['acorn', 'acorn-jsx', 'eslint-visitor-keys'])]
};

Run the build

npm run build

> [email protected] build
> rollup -c rollup.config.js


espree.js → dist/espree.cjs...
created dist/espree.cjs in 636ms

Rename and wrap the generated file

The generated file is named espree.cjs and it is a commonjs module. We can rename it to espree.js and wrap it as a requirejs module which means it has to be wrapped with the following code:

define(function (require, exports, module) {
     // espree code here
});

Copy the bundle

Now you can copy the bundle to this r.js fork repo.

cp dist/espree.js /path/to/r.js/build/jslib/espree.js