Delete stale compiled files.

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

 // Copyright (c) 2014, 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.
 
 import 'dart:io';
 
 import 'package:args/args.dart';
 import 'package:analyzer/src/services/formatter_impl.dart';
 import 'package:async_await/async_await.dart' as async_await;
 import 'package:path/path.dart' as p;
@@ skipping 77 matching lines @@
     stderr.writeln("Could not find compiler commit hash in README.md.");
     exit(1);
   }
 
   lastCommit = match[0];
 
   var numFiles = 0;
   var numCompiled = 0;
 
   // Compile any modified or missing files.
+  var sources = new Set<String>();

[nweiz, 2014/09/10 21:08:18]

Nit: I wouldn't type this.

[Bob Nystrom, 2014/09/10 22:42:34]

Done.

   for (var entry in new Directory(sourceDir).listSync(recursive: true)) {
     if (p.extension(entry.path) != ".dart") continue;
 
     numFiles++;
     var relative = p.relative(entry.path, from: sourceDir);
+    sources.add(relative);
 
     var sourceFile = entry as File;
     var destPath = p.join(generatedDir, relative);
     var destFile = new File(destPath);
     if (force ||
         currentCommit != lastCommit ||
         !destFile.existsSync() ||
         entry.lastModifiedSync().isAfter(destFile.lastModifiedSync())) {
       _compile(sourceFile.path, sourceFile.readAsStringSync(), destPath);
       numCompiled++;
       if (verbose) print("Compiled $relative");
     }
   }
 
+  // Delete any previously compiled files whose source no longer exists.
+  for (var entry in new Directory(generatedDir).listSync(recursive: true)) {
+    if (p.extension(entry.path) != ".dart") continue;

[nweiz, 2014/09/10 21:08:18]

If there are specific non-Dart files we don't want to delete (e.g. the README) I
think we should list them explicitly.

[Bob Nystrom, 2014/09/10 22:42:34]

I think it's better to whitelist this. The compiler only generates .dart files
(and the README, but that's special) so it shouldn't delete random other files
like .DS_Store, etc. I only want it to clean up its own mess.

+
+    var relative = p.relative(entry.path, from: generatedDir);
+
+    if (!sources.contains(relative)) {
+      _deleteFile(entry.path);
+      if (verbose) print("Deleted  $relative");
+    }
+  }
+
   // Update the README.
   if (currentCommit != lastCommit) {
     readme = readme.replaceAll(_commitPattern, currentCommit);
     _writeFile(readmePath, readme);
+    if (verbose) print("Updated README.md");
   }
 
+  if (numCompiled > 0) _generateSnapshot(buildDir);
+
   if (verbose) print("Compiled $numCompiled out of $numFiles files");
 
-  if (numCompiled > 0) _generateSnapshot(buildDir);
-
   if (hadFailure) exit(1);
 }
 
 void _compile(String sourcePath, String source, String destPath) {
   var destDir = new Directory(p.dirname(destPath));
   destDir.createSync(recursive: true);
 
   source = _translateAsyncAwait(sourcePath, source);
   if (source != null) source = _fixDart2jsImports(sourcePath, source, destPath);
 
@@ skipping 85 matching lines @@
 ///
 /// This swallows errors to accommodate multiple compilers running concurrently.
 /// Since they will produce the same output anyway, a failure of one is fine.
 void _writeFile(String path, String contents) {
   try {
     new File(path).writeAsStringSync(contents);
   } on IOException catch (ex) {
     // Do nothing.
   }
 }