rollup-plugin-google-closure-compiler/index.js

Rollup plugin for invoking the Google Closure Compiler with Java.

const tmp = require('tmp');
const fs = require('fs');
const ClosureCompiler = require('google-closure-compiler').compiler;

module.exports = function closure(flags = {}) {
    return {
        name: 'closure-compiler',
        transformBundle(code) {
            const jsFile = tmp.fileSync();
            const mapFile = tmp.fileSync();

            fs.writeFileSync(jsFile.name, code);

            flags = Object.assign({
                js: jsFile.name,
                createSourceMap: mapFile.name,
                processCommonJsModules: true,
            }, flags);

            const compiler = new ClosureCompiler(camelToUnderscore(flags));

            const compile = new Promise(resolve => compiler.run((...args) => resolve(args)));

            return compile.then(([exitCode, stdout, stderr]) => {
                if (exitCode) {
                    throw new Error(`Closure compiler exited code ${exitCode}: ${stderr}`);
                }

                return { code: stdout, map: JSON.parse(fs.readFileSync(mapFile.name)), mapFile: mapFile.name };
            });
        }
    };
}

const camelToUnderscore = camelOptions => {
    const reg = /([A-Z])/g;
    const ret = {};

    Object.keys(camelOptions).forEach(key => {
        const value = camelOptions[key];

        if (reg.test(key)) {
            key = key.replace(reg, char => '_' + char.toLowerCase())
        }

        ret[key] = value;
    });

    return ret;
}