dart2js: add an example script that shows the distribution of code among

pkg/compiler/tool/library_size_split.dart

+// 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.
+
+/// Command-line tool to show the size distribution of generated code among
+/// libraries. Libraries can be grouped using regular expressions. See
+/// [defaultGrouping] for an example.
+library compiler.tool.library_size_split;
+
+import 'dart:convert';
+import 'dart:io';
+import 'dart:math' show max;
+
+import 'package:compiler/src/info/info.dart';
+import 'package:yaml/yaml.dart';
+
+main(args) {
+  if (args.length < 1) {
+    print('usage: dart tool/library_size_split.dart '
+        'path-to-info.json [grouping.yaml]');
+    exit(1);
+  }
+
+  var filename = args[0];
+  var json = JSON.decode(new File(filename).readAsStringSync());
+  var info = AllInfo.parseFromJson(json);
+
+  var groupingText = args.length > 1
+      ? new File(args[1]).readAsStringSync() : defaultGrouping;
+  var groupingYaml = loadYaml(groupingText);
+  var groups = {};
+  for (var group in groupingYaml['groups']) {
+    var name = group['name'];

[Harry Terkelsen, 2015/08/11 01:43:39]

so you can only omit the name for one group?

[Siggi Cherem (dart-lang), 2015/08/11 21:08:00]

Good catch, that was not intentional. I changed this a bit to create a
specification of a group and allowing multiple unnamed groups.

The change also made it easy to add support for clustering groups (something I
wanted to add anyways).

Now that I have that I changed the default grouping to also include individual
libraries. Here is a portion of what the new output for the defaultGrouping in
angular2 helloworld now looks like:



 ...
 package:angular2/src/render/dom/dom_renderer.ng_deps.dart         307   0.06%
 package:angular2/src/core/compiler/view_resolver.dart             310   0.06%
 ...
 dart:html_common                                                 3176   0.57%
 package:angular2/src/core/compiler/view.dart                     3183   0.57%
 package:angular2/src/render/dom/compiler/directive_parser.dart   3417   0.61%
 package:path/src/context.dart                                    3662   0.66%
 ...
 dart:js                                                          5048   0.91%
 ...
 package:intl/intl.dart                                          13504   2.42%
 ...
 dart:async                                                      36312   6.52%
 ----------------------------------------------------------------------------
 path                                                             8800   1.58%
 stack_trace                                                     11481   2.06%
 intl                                                            14126   2.54%
 angular2                                                       220724  39.62%
 -----------------------------------------------------------------------------
 Loose files                                                      2266   0.41%
 Core libs                                                      217634  39.07%
 All packages                                                   255131  45.80%
 -----------------------------------------------------------------------------
 Total (excludes preambles, statics & consts)                   475031  85.27%
 Program Size                                                   557099    100%

+    groups[name] = new RegExp(group['regexp']);
+  }
+
+  var sizes = {};
+  for (LibraryInfo lib in info.libraries) {
+    groups.forEach((name, RegExp regexp) {
+      var m = regexp.firstMatch('${lib.uri}');
+      if (m != null) {
+        if (name == null) name = m.group(1);
+        if (name == null) name = m.group(0);
+        sizes.putIfAbsent(name, () => 0);
+        sizes[name] += lib.size;
+      }
+    });
+  }
+
+  var all = sizes.keys.toList();
+  all.sort((a, b) => sizes[a] - sizes[b]);
+  var realTotal = info.program.size;
+  var longest = all.fold(0, (count, value) => max(count, value.length));
+  for (var name in all) {
+    var size = sizes[name];
+    var percent = (size * 100 / realTotal).toStringAsFixed(2);
+    print(' ${_pad(name, longest + 1, right: true)}'
+          ' ${_pad(size, 8)} ${_pad(percent, 6)}%');
+  }
+}
+
+_pad(value, n, {bool right: false}) {
+  var s = '$value';
+  if (s.length >= n) return s;
+  var pad = ' ' * (n - s.length);
+  return right ? '$s$pad' : '$pad$s';
+}
+
+/// Example grouping specification: a yaml format containing a list of
+/// name/regexp pairs. If the name is omitted, it is assume to be group(1) of

[Harry Terkelsen, 2015/08/11 01:43:39]

or group(0) if there is only 1 group

[Siggi Cherem (dart-lang), 2015/08/11 21:08:00]

Done.

+/// the regexp.
+const defaultGrouping = r"""
+groups:
+- { name: "TOTAL", regexp: ".*" }
+- { name: "Loose files", regexp: "file://.*" }
+- { name: "All packages", regexp: "package:.*" }
+- { name: "Core libs", regexp: "dart:.*" }
+# We omitted `name` to extract the package name from the regexp directly.
+- { regexp: "package:([^/]*)" }
+""";