enable batch mode for dartdevc tests, also fix status so ddc bots pass

pkg/dev_compiler/bin/dartdevc.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.
+/// Command line entry point for Dart Development Compiler (dartdevc), used to
+/// compile a collection of dart libraries into a single JS module
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
+import 'dart:isolate';
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/src/command_line/arguments.dart';
 import 'package:analyzer/src/generated/engine.dart' show AnalysisEngine;
 import 'package:bazel_worker/bazel_worker.dart';
 import 'package:dev_compiler/src/compiler/command.dart';
 
 Future main(List<String> args) async {
   // Always returns a new modifiable list.
   args = preprocessArgs(PhysicalResourceProvider.INSTANCE, args);
 
   if (args.contains('--persistent_worker')) {
-    new _CompilerWorker(args..remove('--persistent_worker')).run();
+    await new _CompilerWorker(args..remove('--persistent_worker')).run();
+  } else if (args.isNotEmpty && args.last == "--batch") {
+    await runBatch(args.sublist(0, args.length - 1));
   } else {
     exitCode = compile(args);
   }
 }
 
 /// Runs the compiler worker loop.
 class _CompilerWorker extends AsyncWorkerLoop {
   /// The original args supplied to the executable.
   final List<String> _startupArgs;
 
   _CompilerWorker(this._startupArgs) : super();
 
   /// Performs each individual work request.
   Future<WorkResponse> performRequest(WorkRequest request) async {
     var args = _startupArgs.toList()..addAll(request.arguments);
 
     var output = new StringBuffer();
     var exitCode = compile(args, printFn: output.writeln);
     AnalysisEngine.instance.clearCaches();
     return new WorkResponse()
       ..exitCode = exitCode
       ..output = output.toString();
   }
 }
+
+Future runBatch(List<String> batchArgs) async {
+  int totalTests = 0;
+  int testsFailed = 0;
+  var watch = new Stopwatch()..start();
+  print('>>> BATCH START');
+  Stream input = stdin.transform(UTF8.decoder).transform(new LineSplitter());

[Bob Nystrom, 2017/08/03 18:28:04]

Can this stream be typed more precisely, or inferred?

Or, perhaps easier, could you use stdin.readLineSync() instead?

[Jennifer Messerly, 2017/08/03 19:43:05]

I just copy+pasted this from the other impls of batch mode (think I took this
from Kernel as it was the simplest). I can change that to say `var`. I don't
know why they're not using `readLineSync`, that's a good idea

[Bob Nystrom, 2017/08/03 20:19:48]

It was added much later in dart:io's evolution than much of the rest of the API,
so it probably wasn't there when they first wrote this code. Also, when it was
added, they didn't really tell anyone about it...

+  await for (String line in input) {
+    if (line.isEmpty) {
+      int time = watch.elapsedMilliseconds;
+      print('>>> BATCH END '
+          '(${totalTests - testsFailed})/$totalTests ${time}ms');
+      break;
+    }
+    ++totalTests;

[Bob Nystrom, 2017/08/03 18:28:04]

Random nit: Maybe it's just me, but I tend to think of postfix "++" as the
default one and only use prefix when I specifically need the prefix semantics.

A quick code search shows 741 prefix ones and 3,596 postfix ones. Not that it
really matters either way.

[Jennifer Messerly, 2017/08/03 19:43:06]

again this is just copied code. I don't mind changing it, but it already exists
like this elsewhere in the repo :)

+    var args = batchArgs.toList()..addAll(line.split(new RegExp(r'\s+')));
+
+    // We don't try/catch here, since `compile` should handle that.
+    var compileExitCode = compile(args);
+    AnalysisEngine.instance.clearCaches();
+    stderr.writeln('>>> EOF STDERR');
+    var outcome = compileExitCode == 0
+        ? 'PASS'
+        : compileExitCode == 70 ? 'CRASH' : 'FAIL';
+    print('>>> TEST $outcome ${watch.elapsedMilliseconds}ms');
+  }
+}