esbuild

#!/usr/bin/env node

// Forward to the automatically-generated WebAssembly loader from the Go compiler

const module_ = require('module');
const crypto = require('crypto');
const path = require('path');
const zlib = require('zlib');
const fs = require('fs');
const os = require('os');

const wasm_exec_node = path.join(__dirname, '..', 'wasm_exec_node.js');
const esbuild_wasm = path.join(__dirname, '..', 'esbuild.wasm');

const code = fs.readFileSync(wasm_exec_node, 'utf8');
const wrapper = new Function('require', 'WebAssembly', code);

function instantiate(bytes, importObject) {
  // Using this API causes "./esbuild --version" to run around 1 second faster
  // than using the "WebAssembly.instantiate()" API when run in node (v12.16.2)
  const module = new WebAssembly.Module(bytes);
  const instance = new WebAssembly.Instance(module, importObject);
  return Promise.resolve({ instance, module });
}

// Node has an unfortunate bug where the node process is unnecessarily kept open while a
// WebAssembly module is being optimized: https://github.com/nodejs/node/issues/36616.
// This means cases where running "esbuild" should take a few milliseconds can end up
// taking many seconds instead. To work around this bug, it is possible to force node to
// exit by calling the operating system's exit function. That's what this code does.
process.on('exit', code => {
  // If it's a non-zero exit code, we can just kill our own process to stop. This will
  // preserve the fact that there is a non-zero exit code although the exit code will
  // be different. We cannot use this if the exit code is supposed to be zero.
  if (code !== 0) {
    try {
      process.kill(process.pid, 'SIGINT');
    } catch (e) {
    }
    return;
  }

  // Otherwise if the exit code is zero, try to fall back to a binary N-API module that
  // calls the operating system's "exit(0)" function.
  const nativeModule = `${process.platform}-${os.arch()}-${os.endianness()}.node`;
  const base64 = require('../exit0')[nativeModule];
  if (base64) {
    try {
      const data = zlib.inflateRawSync(Buffer.from(base64, 'base64'));
      const hash = crypto.createHash('sha256').update(base64).digest().toString('hex').slice(0, 16);
      const tempFile = path.join(os.tmpdir(), `${hash}-${nativeModule}`);
      try {
        if (fs.readFileSync(tempFile).equals(data)) {
          require(tempFile);
        }
      } finally {
        fs.writeFileSync(tempFile, data);
        require(tempFile);
      }
    } catch (e) {
    }
  }
});

// Node has another bug where using "fs.read" to read from stdin reads
// everything successfully and then throws an error, but only on Windows. Go's
// WebAssembly support uses "fs.read" so it hits this problem. This is a patch
// to try to work around the bug in node. This bug has been reported to node
// at least twice in https://github.com/nodejs/node/issues/35997 and in
// https://github.com/nodejs/node/issues/19831. This issue has also been
// reported to the Go project: https://github.com/golang/go/issues/43913.
const read = fs.read;
fs.read = function () {
  const callback = arguments[5];
  arguments[5] = function (err, count) {
    if (count === 0 && err && err.code === 'EOF') {
      arguments[0] = null;
    }
    return callback.apply(this, arguments);
  };
  return read.apply(this, arguments);
};

// Hack around a Unicode bug in node: https://github.com/nodejs/node/issues/24550.
// See this for the matching Go issue: https://github.com/golang/go/issues/43917.
const write = fs.write;
fs.write = function (fd, buf, offset, length, position, callback) {
  if (offset === 0 && length === buf.length && position === null) {
    if (fd === process.stdout.fd) {
      try {
        process.stdout.write(buf, err => err ? callback(err, 0, null) : callback(null, length, buf));
      } catch (err) {
        callback(err, 0, null);
      }
      return;
    }
    if (fd === process.stderr.fd) {
      try {
        process.stderr.write(buf, err => err ? callback(err, 0, null) : callback(null, length, buf));
      } catch (err) {
        callback(err, 0, null);
      }
      return;
    }
  }
  return write.apply(this, arguments);
};
const writeSync = fs.writeSync;
fs.writeSync = function (fd, buf) {
  if (fd === process.stdout.fd) return process.stdout.write(buf), buf.length;
  if (fd === process.stderr.fd) return process.stderr.write(buf), buf.length;
  return writeSync.apply(this, arguments);
};

// WASM code generated with Go 1.17.2+ will crash when run in a situation with
// many environment variables: https://github.com/golang/go/issues/49011. An
// example of this situation is running a Go-compiled WASM executable in GitHub
// Actions. Work around this by filtering node's copy of environment variables
// down to only include the environment variables that esbuild currently uses.
const esbuildUsedEnvVars = [
  'NO_COLOR',
  'NODE_PATH',
  'npm_config_user_agent',
  'WT_SESSION',
]
for (let key in process.env) {
  if (esbuildUsedEnvVars.indexOf(key) < 0) {
    delete process.env[key]
  }
}

process.argv.splice(2, 0, esbuild_wasm);
wrapper(module_.createRequire(wasm_exec_node), Object.assign(Object.create(WebAssembly), { instantiate }));