server/app/ws/routes/fs.release.js

const fs = require('fs')

const exists = async file => {
    return new Promise(res => {
        fs.promises.stat(file).then(() => res(true)).catch(() => res(false))
    })
}

module.exports = exports = async (message, di) => {
    const { descriptor } = message.data()

    const node_uuid = message.socket.session.file_descriptors?.[descriptor]
    if ( node_uuid ) {
        delete message.socket.session.file_descriptors[descriptor]
    }

    const placeholders = message.socket.session.temp_write_files?.[descriptor]
    if ( placeholders ) {
        for ( const placeholder of placeholders ) {
            if ( await exists(placeholder.path) ) {
                await fs.promises.unlink(placeholder.path)
            }
        }

        delete message.socket.session.temp_write_files[descriptor]
    }

    message.send_response(
        message.fresh()
    )
}