Polymer transformer logs now show on the frontend for pub serve.

pkg/polymer/lib/src/build/log_injector.dart

+// Copyright (c) 2013, 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.
+
+/// This library provides a single function called injectLogs which when called
+/// will request a logs json file and build a small widget out of them which
+/// groups the logs by level.
+library polymer.build.log_injector;
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:html';
+
+import 'package:path/path.dart' as path;
+
+class LogInjector {
+  Element selectedMenu;
+  Element selectedContent;
+
+  // Gets the logs from a url and inject them into the dom.
+  Future injectLogsFromUrl([String url]) {
+    if (url == null) url = '${Uri.base.path}._buildLogs';
+    return HttpRequest.getString(url).then((data) => injectLogs(data));
+  }
+
+  // Builds the html for the logs element given some logs, and injects that
+  // into the dom. Currently, we do not  use Polymer just to ensure that the
+  // page works regardless of the state of the app. Ideally, we could have
+  // multiple scripts running independently so we could ensure that this would
+  // always be running.
+  injectLogs(String data) {
+    // Group all logs by level.
+    var logsByLevel = {
+    };
+    JSON.decode(data).forEach((log) {
+      logsByLevel.putIfAbsent(log['level'], () => []);
+      logsByLevel[log['level']].add(log);
+    });
+    if (logsByLevel.isEmpty) return;
+
+    // Build the wrapper, menu, and content divs.
+
+    var menuWrapper = new DivElement()
+      ..classes.add('menu');
+    var contentWrapper = new DivElement()
+      ..classes.add('content');
+    var wrapperDiv = new DivElement()
+      ..classes.add('build-logs')
+      ..append(menuWrapper)
+      ..append(contentWrapper);
+
+    // For each log level, add a menu item, content section, and all the logs.
+    logsByLevel.forEach((level, logs) {
+      var levelClassName = level.toLowerCase();
+
+      // Add the menu item and content item.
+      var menuItem = new Element.html(
+          '<div class="$levelClassName">'
+          '$level <span class="num">(${logs.length})</span>'
+          '</div>');
+      menuWrapper.append(menuItem);
+      var contentItem = new DivElement()
+        ..classes.add(levelClassName);
+      contentWrapper.append(contentItem);
+
+      // Set up the click handlers.
+      menuItem.onClick.listen((_) {
+        if (selectedMenu == menuItem) {
+          selectedMenu = null;
+          selectedContent = null;
+        } else {
+          if (selectedMenu != null) {
+            selectedMenu.classes.remove('active');
+            selectedContent.classes.remove('active');
+          }
+
+          selectedMenu = menuItem;
+          selectedContent = contentItem;
+        }
+
+        menuItem.classes.toggle('active');
+        contentItem.classes.toggle('active');
+      });
+
+      // Add the logs to the content item.
+      for (var log in logs) {
+        var logHtml = new StringBuffer();
+        logHtml.write('<div class="log">');
+        logHtml.write(
+            '<div class="message $levelClassName">${log['message']}</div>');
+        var assetId = log['assetId'];
+        if (assetId != null) {
+          logHtml.write(
+              '<div class="asset">'
+              '  <span class="package">${assetId['package']}</span>:'
+              '  <span class="path">${assetId['path']}</span>''</div>');
+        }
+        var span = log['span'];
+        if (span != null) {
+          logHtml.write(
+              '<div class="span">'
+              '  <div class="location">${span['location']}</div>'
+              '  <code class="text">${span['text']}</code>''</div>');
+        }
+        logHtml.write('</div>');
+
+        contentItem.append(new Element.html(logHtml.toString()));
+      };
+    });
+
+    document.body.append(wrapperDiv);
+  }
+
+}