web/main.dart

#!/usr/bin/env dart
// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/// Command line entry point for Dart Development Compiler (dartdevc).
///
/// Supported commands are
///   * compile: builds a collection of dart libraries into a single JS module
///
/// Additionally, these commands are being considered
///   * link:  combines several JS modules into a single JS file
///   * build: compiles & links a set of code, automatically determining
///            appropriate groupings of libraries to combine into JS modules
///   * watch: watch a directory and recompile build units automatically
///   * serve: uses `watch` to recompile and exposes a simple static file server
///            for local development
///
/// These commands are combined so we have less names to expose on the PATH,
/// and for development simplicity while the precise UI has not been determined.
///
/// A more typical structure for web tools is simply to have the compiler with
/// "watch" as an option. The challenge for us is:
///
/// * Dart used to assume whole-program compiles, so we don't have a
///   user-declared unit of building, and neither "libraries" or "packages" will
///   work,
/// * We do not assume a `node` JS installation, so we cannot easily reuse
///   existing tools for the "link" step, or assume users have a local
///   file server,
/// * We didn't have a file watcher API at first,
/// * We had no conventions about where compiled output should go (or even
///   that we would be compiling at all, vs running on an in-browser Dart VM),
/// * We wanted a good first impression with our simple examples, so we used
///   local file servers, and users have an expectation of it now, even though
///   it doesn't scale to typical apps that need their own real servers.

@JS()
library dev_compiler.web.main;

import 'dart:async';

import 'package:args/command_runner.dart';
import 'package:js/js.dart';

import 'web_command.dart';

@JS()
external set setUpCompilerInBrowser(Function function);

Future main() async {
  var args = ['compile'];
  _runCommand(args);
}

/// Runs a single compile command, and returns an exit code.
Future<int> _runCommand(List<String> args,
    {MessageHandler messageHandler}) async {
  try {
    // TODO: Remove CommandRunner and args if possible. May run into issues
    // with ArgResults or ArgParsers.
    var runner = new CommandRunner('dartdevc', 'Dart Development Compiler');
    runner.addCommand(new WebCompileCommand(messageHandler: messageHandler));
    setUpCompilerInBrowser = allowInterop(await runner.run(args));
  } catch (e, s) {
    return _handleError(e, s, args, messageHandler: messageHandler);
  }
  return 1;
}

/// Handles [error] in a uniform fashion. Returns the proper exit code and calls
/// [messageHandler] with messages.
int _handleError(dynamic error, dynamic stackTrace, List<String> args,
    {MessageHandler messageHandler}) {
  messageHandler ??= print;

  if (error is UsageException) {
    // Incorrect usage, input file not found, etc.
    messageHandler(error);
    return 64;
  } else if (error is CompileErrorException) {
    // Code has error(s) and failed to compile.
    messageHandler(error);
    return 1;
  } else {
    // Anything else is likely a compiler bug.
    //
    // --unsafe-force-compile is a bit of a grey area, but it's nice not to
    // crash while compiling
    // (of course, output code may crash, if it had errors).
    //
    messageHandler("");
    messageHandler("We're sorry, you've found a bug in our compiler.");
    messageHandler("You can report this bug at:");
    messageHandler("    https://github.com/dart-lang/dev_compiler/issues");
    messageHandler("");
    messageHandler(
        "Please include the information below in your report, along with");
    messageHandler(
        "any other information that may help us track it down. Thanks!");
    messageHandler("");
    messageHandler("    dartdevc arguments: " + args.join(' '));
    messageHandler("");
    messageHandler("```");
    messageHandler(error);
    messageHandler(stackTrace);
    messageHandler("```");
    return 70;
  }
}