add tool to check that deferred libraries contain the expected code

bin/deferred_library_check.dart

Index: bin/deferred_library_check.dart
diff --git a/bin/deferred_library_check.dart b/bin/deferred_library_check.dart
new file mode 100644
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--- /dev/null
+++ b/bin/deferred_library_check.dart
@@ -0,0 +1,144 @@
+// Copyright (c) 2015, 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.
+
+/// A command-line tool that verifies that deferred libraries split the code as
+/// expected.
+/// This tool checks that the output from dart2js meets a given specification,
+/// given in a YAML file. The format of the YAML file is:
+///
+///     main:
+///       packages:
+///         - some_package
+///         - other_package
+///
+///     foo:
+///       packages:
+///         - foo
+///         - bar
+///
+///     baz:
+///       packages:
+///         - baz
+///         - quux
+///
+/// The YAML file consists of a list of declarations, one for each deferred
+/// part expected in the output. At least one of these parts must be named
+/// "main"; this is the main part that contains the program entrypoint. Each
+/// top-level part contains a list of package names that are expected to be
+/// contained in that part. Any package that is not explicitly listed is
+/// expected to be in the main part. For instance, in the example YAML above
+/// the part named "baz" is expected to contain the packages "baz" and "quux".
+///
+/// The names for parts given in the specification YAML file (besides "main")
+/// are arbitrary and just used for reporting when the output does not meet the
+/// specification.
+library dart2js_info.bin.deferred_library_check;
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:dart2js_info/info.dart';
+import 'package:quiver/collection.dart';
+import 'package:yaml/yaml.dart';
+
+Future main(List<String> args) async {
+  if (args.length < 2) {
+    usage();
+    exit(1);
+  }
+  var info = await infoFromFile(args[0]);
+  var manifest = await manifestFromFile(args[1]);
+
+  // For each part in the manifest, record the expected "packages" for that
+  // part.
+  var packages = <String, String>{};
+  for (var part in manifest.keys) {
+    for (var package in manifest[part]['packages']) {
+      if (packages.containsKey(package)) {
+        print('You cannot specify that package "$package" maps to both parts '
+            '"$part" and "${packages[package]}".');
+        exit(1);
+      }
+      packages[package] = part;
+    }
+  }
+
+  var guessedPartMapping = new BiMap<String, String>();
+  guessedPartMapping['main'] = 'main';
+
+  bool anyFailed = false;
+
+  checkInfo(BasicInfo info) {
+    var lib = getLibraryOf(info);
+    if (lib != null && isPackageUri(lib.uri)) {
+      var packageName = getPackageName(lib.uri);
+      var outputUnitName = info.outputUnit.name;
+      var expectedPart;
+      if (packages.containsKey(packageName)) {
+        expectedPart = packages[packageName];
+      } else {
+        expectedPart = 'main';
+      }
+      var expectedOutputUnit = guessedPartMapping[expectedPart];
+      if (expectedOutputUnit == null) {
+        guessedPartMapping[expectedPart] = outputUnitName;
+      } else {
+        if (expectedOutputUnit != outputUnitName) {
+          // TODO(het): add options for how to treat unspecified packages
+          if (!packages.containsKey(packageName)) {
+            print('"${info.name}" from package "$packageName" was not declared '
+                'to be in an explicit part but was not in the main part');
+          } else {
+            var actualPart = guessedPartMapping.inverse[outputUnitName];
+            print('"${info.name}" from package "$packageName" was specified to '
+                'be in part $expectedPart but is in part $actualPart');
+          }
+          anyFailed = true;
+        }
+      }
+    }
+  }
+
+  info.functions.forEach(checkInfo);
+  info.fields.forEach(checkInfo);
+  if (anyFailed) {
+    print('The dart2js output did not meet the specification.');
+  } else {
+    print('The dart2js output meets the specification');
+  }
+}
+
+LibraryInfo getLibraryOf(Info info) {
+  var current = info;
+  while (current is! LibraryInfo) {
+    if (current == null) {
+      return null;
+    }
+    current = current.parent;
+  }
+  return current;
+}
+
+bool isPackageUri(Uri uri) => uri.scheme == 'package';
+
+String getPackageName(Uri uri) {
+  assert(isPackageUri(uri));
+  return uri.pathSegments.first;
+}
+
+Future<AllInfo> infoFromFile(String fileName) async {
+  var file = await new File(fileName).readAsString();
+  return new AllInfoJsonCodec().decode(JSON.decode(file));
+}
+
+Future manifestFromFile(String fileName) async {
+  var file = await new File(fileName).readAsString();
+  return loadYaml(file);
+}
+
+void usage() {
+  print('''
+usage: dart2js_info_deferred_library_check dump.info.json manifest.yaml''');
+}