C amalgamator for the Boehm garbage collector

amalgamator.js

const ENTRYPOINTS = ['extra/gc.c', 'include/gc.h']

const fs = require('fs')
const path = require('path')

const search_dirs = ['.', 'extra', 'include', 'include/private', 'include/extra']
function find(file) {
    file = file.substring(file.lastIndexOf('/') + 1)
    for (const dir of search_dirs) {
        if (fs.readdirSync(dir).includes(file)) return path.join(dir, file)
    }
    return file
}

const included_files = []
function amalgamate(line) {
    const m = line.match(/#\s*include "(.+?)"/)
    if (!m) return line
    const p = find(m[1])
    if (included_files.includes(p)) return ''
    included_files.push(p)
    try {
        return fs.readFileSync(p, 'utf-8')
                 .split('\n')
                 .map(amalgamate)
                 .join('\n')
    } catch {
        return line
    }
}
for (const entrypoint of ENTRYPOINTS) {
    const gc_source = fs.readFileSync(entrypoint, 'utf-8')
    const copyright_header = gc_source.match(/\/\*[\s\S]+?\*\//)[0]

    let amalgamated_source = gc_source.split('\n').map(amalgamate).join('\n')

    if (process.argv.find(it => it === '-m' || it === '--minify')) {
        amalgamated_source = amalgamated_source
            // remove comments
            .replace(/\/\*[\s\S]+?\*\//g, '')
            .replace(/\/\/.+/g, '')

            .replace(/\\\n\s+/g, '') // escaped newlines
            .replace(/^# +/gm, '#') // `# define` -> `#define`
            .replace(/ *(\+|\*|\/|\+\+|\-\-|\+=|\-=|\*=|\/=|%=|=|==|!=|&&|\|\||\?|\:|!|&|\||\^|<<|>>|;|<=|>=|<<=|>>=|&=|\|=|\^=|,|->|\)) */g, '$1') // remove spaces around infix ops
            .replace(/"\n"/g, '') // remove concatenated string literals spanning multiple lines
            .replace(/  +/g, ' ') // replace multiple spaces with just one
            .split('\n')
            .map(it => it.trim()) // trim whitespace around each line
            .filter(it => it !== '') // remove empty lines
            .join('\n');
    }

    fs.mkdirSync('dist', { recursive: true })
    fs.writeFileSync(`dist/${path.basename(entrypoint)}`, `${copyright_header}\n\n${amalgamated_source}\n`)
}

.filter(Boolean) ?

it's the same as .filter(it => !!it) / .filter(it => it !== '') :)