babel-node.js

/**
 * This tiny wrapper file checks for known node flags and appends them
 * when found, before invoking the "real" _babel-node(1) executable.
 */

import getV8Flags from "v8flags";
import path from "path";

// TODO: When support for node < 10.10 will be dropped, this package
// can be replaced with process.allowedNodeEnvironmentFlags
import allowedNodeEnvironmentFlags from "node-environment-flags";

let args = [path.join(__dirname, "_babel-node")];

let babelArgs = process.argv.slice(2);
let userArgs;

// separate node arguments from script arguments
const argSeparator = babelArgs.indexOf("--");
if (argSeparator > -1) {
  userArgs = babelArgs.slice(argSeparator); // including the  --
  babelArgs = babelArgs.slice(0, argSeparator);
}

/**
 * Replace dashes with underscores in the v8Flag name
 * Also ensure that if the arg contains a value (e.g. --arg=true)
 * that only the flag is returned.
 */
function getNormalizedV8Flag(arg) {
  // v8 uses the "no" prefix to negate boolean flags (e.g. --nolazy),
  // but they are not listed by v8flags
  const matches = arg.match(/--(?:no)?(.+)/);

  if (matches) {
    return `--${matches[1].replace(/-/g, "_")}`;
  }

  return arg;
}

// These are aliases for node options defined by babel-node.
const aliases = new Map([
  ["-d", "--debug"],
  ["-gc", "--expose-gc"],
]);

getV8Flags(function(err, v8Flags) {
  for (let i = 0; i < babelArgs.length; i++) {
    const arg = babelArgs[i];
    const flag = arg.split("=")[0];

    if (flag === "-r" || flag === "--require") {
      args.push(flag);
      args.push(babelArgs[++i]);
    } else if (aliases.has(flag)) {
      args.unshift(aliases.get(flag));
    } else if (
      flag === "debug" || // node debug foo.js
      flag === "inspect" ||
      v8Flags.indexOf(getNormalizedV8Flag(flag)) >= 0 ||
      allowedNodeEnvironmentFlags.has(flag)
    ) {
      args.unshift(arg);
    } else {
      args.push(arg);
    }
  }

  // append arguments passed after --
  if (argSeparator > -1) {
    args = args.concat(userArgs);
  }

  try {
    const kexec = require("kexec");
    kexec(process.argv[0], args);
  } catch (err) {
    if (
      err.code !== "MODULE_NOT_FOUND" &&
      err.code !== "UNDECLARED_DEPENDENCY"
    ) {
      throw err;
    }

    const child_process = require("child_process");
    const proc = child_process.spawn(process.argv[0], args, {
      stdio: "inherit",
      cwd: process.cwd(),
    });
    proc.on("exit", function(code, signal) {
      process.on("exit", function() {
        if (signal) {
          process.kill(process.pid, signal);
        } else {
          process.exit(code);
        }
      });
    });
    process.on("SIGINT", () => proc.kill("SIGINT"));
  }
});