Hook async/await compiler into pub and use it.

sdk/lib/_internal/pub/bin/async_compile.dart

Index: sdk/lib/_internal/pub/bin/async_compile.dart
diff --git a/sdk/lib/_internal/pub/bin/async_compile.dart b/sdk/lib/_internal/pub/bin/async_compile.dart
index 40280a674281cfce611cdd815cdfaa215ccb3827..0b008ab4a16faa130458fd259d72f2a9886af6e8 100644
--- a/sdk/lib/_internal/pub/bin/async_compile.dart
+++ b/sdk/lib/_internal/pub/bin/async_compile.dart
@@ -4,6 +4,7 @@
 
 import 'dart:io';
 
+import 'package:async_await/async_await.dart' as async_await;
 import 'package:path/path.dart' as p;
 
 /// The path to pub's root directory (sdk/lib/_internal/pub) in the Dart repo.
@@ -17,6 +18,9 @@ final sourceUrl = p.toUri(sourceDir).toString();
 /// The directory that compiler output should be written to.
 String buildDir;
 
+/// `true` if any file failed to compile.
+bool hadFailure = false;
+
 /// This runs the async/await compiler on all of the pub source code.
 ///
 /// It reads from the repo and writes the compiled output into the given build
@@ -62,6 +66,8 @@ void main(List<String> arguments) {
   }
 
   if (!silent) print("Compiled $numCompiled out of $numFiles files.");
+
+  if (hadFailure) exit(1);
 }
 
 final _compilerPattern = new RegExp(r"import '(\.\./)+compiler");
@@ -70,8 +76,30 @@ void compile(String sourcePath, String source, String destPath) {
   var destDir = new Directory(p.dirname(destPath));
   destDir.createSync(recursive: true);
 
-  // TODO(rnystrom): Do real async/await transformation here!
-  source = source.replaceAll("ASYNC!", "");
+  if (p.isWithin(p.join(sourceDir, "asset"), sourcePath)) {
+    // Don't run the async compiler on the special "asset" source files. These
+    // have preprocessor comments that get discarded by the compiler.

[nweiz, 2014/08/27 20:10:07]

Maybe factor this into a function so you can short-circuit here?

[Bob Nystrom, 2014/08/27 21:35:31]

Done.

+  } else {
+    try {
+      source = async_await.compile(source);
+    } catch (ex) {
+      stderr.writeln("Async compile failed on $sourcePath:\n$ex");
+      hadFailure = true;
+
+      // If the async compile fails, delete the file so that we don't try to
+      // run the stale previous output and so that we try to recompile it later.
+      try {
+        new File(destPath).deleteSync();
+      } on IOException catch (ex) {
+        // Do nothing. This may happen if two instances of the compiler are running

[nweiz, 2014/08/27 20:10:07]

Long lines.

[Bob Nystrom, 2014/08/27 21:35:32]

Done.

+        // concurrently and compile the same file. The second one to try to write
+        // the output may fail if the file is still open. Since they are producing

[nweiz, 2014/08/27 20:10:07]

"write the output" -> "delete the file"

[Bob Nystrom, 2014/08/27 21:35:32]

Done.

+        // the same output anyway, just ignore it when the second one fails.
+      }
+
+      return;
+    }
+  }
 
   // Pub imports dart2js using relative imports that reach outside of pub's
   // source tree. Since the build directory is in a different location, we need