Update the analysis server diagnostic page - re-enable code completion and overlay pages,

pkg/analysis_server/lib/src/status/diagnostics.dart

+// Copyright (c) 2017, 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:convert';
+import 'dart:io';
+
+import 'package:analysis_server/protocol/protocol_generated.dart';
+import 'package:analysis_server/src/analysis_server.dart';
+import 'package:analysis_server/src/domain_completion.dart';
+import 'package:analysis_server/src/domain_execution.dart';
+import 'package:analysis_server/src/plugin/plugin_manager.dart';
+import 'package:analysis_server/src/server/http_server.dart';
+import 'package:analysis_server/src/services/completion/completion_performance.dart';
+import 'package:analysis_server/src/socket_server.dart';
+import 'package:analysis_server/src/status/pages.dart';
+import 'package:analyzer/exception/exception.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/instrumentation/instrumentation.dart';
+import 'package:analyzer/source/package_map_resolver.dart';
+import 'package:analyzer/source/sdk_ext.dart';
+import 'package:analyzer/src/context/source.dart';
+import 'package:analyzer/src/dart/analysis/driver.dart';
+import 'package:analyzer/src/dart/analysis/file_state.dart';
+import 'package:analyzer/src/dart/sdk/sdk.dart';
+import 'package:analyzer/src/generated/engine.dart';
+import 'package:analyzer/src/generated/sdk.dart';
+import 'package:analyzer/src/generated/source.dart';
+import 'package:analyzer/src/generated/utilities_general.dart';
+import 'package:plugin/plugin.dart';
+
+final String kCustomCss = '''
+.lead, .page-title+.markdown-body>p:first-child {
+  margin-bottom: 30px;
+  font-size: 20px;
+  font-weight: 300;
+  color: #555;
+}
+
+.container {
+  width: 1160px;
+}
+    
+.masthead {
+  padding-top: 1rem;
+  padding-bottom: 1rem;
+  margin-bottom: 1.5rem;
+  text-align: center;
+  background-color: #4078c0;
+}
+
+.masthead .masthead-logo {
+  display: inline-block;
+  font-size: 1.5rem;
+  color: #fff;
+  float: left;
+}
+
+.masthead-nav {
+  float: right;
+  margin-top: .5rem;
+}
+
+.masthead-nav a:not(:last-child) {
+  margin-right: 1.25rem;
+}
+
+.masthead a {
+  color: rgba(255,255,255,0.5);
+  font-size: 1rem;
+}
+
+.masthead a:hover {
+  color: #fff;
+  text-decoration: none;
+}
+
+.masthead-nav .active {
+  color: #fff;
+  font-weight: 500;
+}
+
+.counter {
+  display: inline-block;
+  padding: 2px 5px;
+  font-size: 11px;
+  font-weight: bold;
+  line-height: 1;
+  color: #666;
+  background-color: #eee;
+  border-radius: 20px;
+}
+
+.menu-item .counter {
+  float: right;
+  margin-left: 5px;
+}    
+    
+td.right {
+  text-align: right;
+}
+
+td.pre {
+  white-space: pre;
+}
+
+.nowrap {
+  white-space: nowrap;
+}
+
+.footer {
+  padding-top: 3rem;
+  padding-bottom: 3rem;
+  margin-top: 3rem;
+  line-height: 1.75;
+  color: #7a7a7a;
+  border-top: 1px solid #eee;
+}
+
+.footer strong {
+  color: #333;
+}
+''';
+
+class DiagnosticsSite extends Site implements AbstractGetHandler {
+  /// An object that can handle either a WebSocket connection or a connection
+  /// to the client over stdio.
+  SocketServer socketServer;
+
+  /// The last few lines printed.
+  List<String> lastPrintedLines = <String>[];
+
+  DiagnosticsSite(this.socketServer, this.lastPrintedLines)
+      : super('Analysis Server') {
+    pages.add(new CompletionPage(this));
+    pages.add(new CommunicationsPage(this));
+    pages.add(new ContextsPage(this));
+    pages.add(new ExecutionDomainPage(this));
+    pages.add(new OverlaysPage(this));
+    pages.add(new ProfilePage(this));
+    //pages.add(new ExceptionsPage(this));
+    pages.add(new InstrumentationPage(this));
+    pages.add(new PluginsPage(this));
+
+    pages.sort(((Page a, Page b) =>
+        a.title.toLowerCase().compareTo(b.title.toLowerCase())));
+
+    // Add the status page at the beginning.
+    pages.insert(0, new StatusPage(this));
+
+    // Add non-nav pages.
+    pages.add(new FeedbackPage(this));
+  }
+
+  String get customCss => kCustomCss;
+
+  Page createUnknownPage(String unknownPath) =>
+      new NotFoundPage(this, unknownPath);
+
+  Page createExceptionPage(String message, StackTrace trace) =>
+      new ExceptionPage(this, message, trace);
+}
+
+/// A page with a proscriptive notion of layout.
+abstract class DiagnosticPage extends Page {
+  final Site site;
+
+  DiagnosticPage(this.site, String id, String title, {String description})
+      : super(id, title, description: description);
+
+  AnalysisServer get server =>
+      (site as DiagnosticsSite).socketServer.analysisServer;
+
+  void generatePage(Map<String, String> params) {
+    buf.writeln('<!DOCTYPE html><html lang="en">');
+    buf.write('<head>');
+    buf.write('<meta charset="utf-8">');
+    buf.write('<meta name="viewport" content="width=device-width, '
+        'initial-scale=1.0">');
+    buf.writeln('<title>${site.title}</title>');
+    buf.writeln('<link rel="stylesheet" '
+        'href="https://cdnjs.cloudflare.com/ajax/libs/Primer/6.0.0/build.css">');
+    buf.writeln('<link rel="stylesheet" '
+        'href="https://cdnjs.cloudflare.com/ajax/libs/octicons/4.4.0/font/octicons.css">');
+    buf.writeln('<script type="text/javascript" '
+        'src="https://www.gstatic.com/charts/loader.js"></script>');
+    buf.writeln('<style>${site.customCss}</style>');
+    buf.writeln('</head>');
+
+    buf.writeln('<body>');
+    generateHeader();
+    buf.writeln('<div class="container">');
+    generateContainer(params);
+    generateFooter();
+    buf.writeln('</div>'); // div.container
+    buf.writeln('</body>');
+    buf.writeln('</html>');
+  }
+
+  void generateHeader() {
+    buf.writeln('''
+    <header class="masthead">
+    <div class="container">
+      <span class="masthead-logo">
+      <span class="mega-octicon octicon-database"></span>
+        ${site.title} Diagnostics
+      </span>
+
+      <nav class="masthead-nav">
+        <a href="/status" ${isNavPage ? ' class="active"' : ''}>Diagnostics</a>
+        <a href="/feedback" ${isCurrentPage('/feedback') ? ' class="active"' : ''}>Feedback</a>
+        <a href="https://www.dartlang.org/tools/analyzer" target="_blank">Docs</a>
+        <a href="https://htmlpreview.github.io/?https://github.com/dart-lang/sdk/blob/master/pkg/analysis_server/doc/api.html" target="_blank">Spec</a>
+      </nav>
+    </div>
+    </header>
+''');
+  }
+
+  void generateContainer(Map<String, String> params) {
+    buf.writeln('<div class="columns docs-layout">');
+    buf.writeln('<div class="three-fourths column markdown-body">');
+    h1(title, classes: 'page-title');
+    div(() {
+      p(description);
+      generateContent(params);
+    }, classes: 'markdown-body');
+    buf.writeln('</div>');
+    buf.writeln('</div>');
+  }
+
+  void generateContent(Map<String, String> params);
+
+  void generateFooter() {
+    buf.writeln('''
+    <footer class="footer">
+      Dart ${site.title} <span style="float:right">SDK ${_sdkVersion}</span>
+    </footer>    
+''');
+  }
+
+  bool get isNavPage => false;
+}
+
+abstract class DiagnosticPageWithNav extends DiagnosticPage {
+  DiagnosticPageWithNav(Site site, String id, String title,
+      {String description})
+      : super(site, id, title, description: description);
+
+  void generateContainer(Map<String, String> params) {
+    buf.writeln('<div class="columns docs-layout">');
+
+    buf.writeln('<div class="one-fifth column">');
+    buf.writeln('<nav class="menu docs-menu">');
+    for (Page page in site.pages.where((p) => p is DiagnosticPageWithNav)) {
+      buf.write('<a class="menu-item ${page == this ? ' selected' : ''}" '
+          'href="${page.path}">${escape(page.title)}');
+      String detail = (page as DiagnosticPageWithNav).navDetail;
+      if (detail != null) {
+        buf.write('<span class="counter">$detail</span>');
+      }
+      buf.writeln('</a>');
+    }
+    buf.writeln('</nav>');
+    buf.writeln('</div>');
+
+    buf.writeln('<div class="four-fifths column markdown-body">');
+    h1(title, classes: 'page-title');
+    div(() {
+      p(description);
+      generateContent(params);
+    }, classes: 'markdown-body');
+    buf.writeln('</div>');
+
+    buf.writeln('</div>');
+  }
+
+  String get navDetail => null;
+
+  bool get isNavPage => true;
+}
+
+class NotFoundPage extends DiagnosticPage {
+  final String path;
+
+  NotFoundPage(Site site, this.path)
+      : super(site, '', '404 Not found', description: "'$path' not found.");
+
+  void generateContent(Map<String, String> params) {}
+}
+
+class ExceptionPage extends DiagnosticPage {
+  final StackTrace trace;
+
+  ExceptionPage(Site site, String message, this.trace)
+      : super(site, '', '500 Oops', description: message);
+
+  void generateContent(Map<String, String> params) {
+    p(trace.toString(), style: 'white-space: pre');
+  }
+}
+
+class FeedbackPage extends DiagnosticPage {
+  FeedbackPage(DiagnosticsSite site)
+      : super(site, 'feedback', 'Feedback',
+            description: 'Providing feedback and filing issues.');
+
+  @override
+  void generateContent(Map<String, String> params) {
+    final String issuesUrl = 'https://github.com/dart-lang/sdk/issues';
+    p(
+      'To file issues or feature requests, see our '
+          '<a href="$issuesUrl">bug tracker</a>. When filing an issue, please describe:',
+      raw: true,
+    );
+    ul([
+      'what you were doing',
+      'what occured',
+      'what you think the expected behavior should have been',
+    ], (line) => buf.writeln(line));
+
+    p('Other data to include:');
+    ul([
+      "the IDE you are using and it's version",
+      'the Dart SDK version (<code>${escape(_sdkVersion)}</code>)',
+      'your operating system (<code>${escape(Platform.operatingSystem)}</code>)',
+    ], (line) => buf.writeln(line));
+
+    p('Thanks!');
+  }
+}
+
+class StatusPage extends DiagnosticPageWithNav {
+  StatusPage(DiagnosticsSite site)
+      : super(site, 'status', 'Status',
+            description:
+                'General status and diagnostics for the analysis server.');
+
+  @override
+  void generateContent(Map<String, String> params) {
+    buf.writeln('<div class="columns">');
+
+    buf.writeln('<div class="column one-half">');
+    h3('Status');
+    buf.writeln(writeOption(
+        'New analysis driver enabled', server.options.enableNewAnalysisDriver));
+    buf.writeln(writeOption('Instrumentation enabled',
+        AnalysisEngine.instance.instrumentationService.isActive));
+    buf.writeln(writeOption('Server process ID', pid));
+    buf.writeln('</div>');
+
+    buf.writeln('<div class="column one-half">');
+    h3('Versions');
+    buf.writeln(writeOption('Analysis server version', AnalysisServer.VERSION));
+    buf.writeln(writeOption('Dart SDK', Platform.version));
+    buf.writeln('</div>');
+
+    buf.writeln('</div>');
+
+    h3('Server domain subscriptions');
+    ul(ServerService.VALUES, (item) {
+      if (server.serverServices.contains(item)) {
+        buf.write('$item (has subscriptions)');
+      } else {
+        buf.write('$item (no subscriptions)');
+      }
+    });
+
+    h3('Analysis domain subscriptions');
+    for (AnalysisService service in AnalysisService.VALUES) {
+      buf.writeln('${service.name}<br>');
+      ul(server.analysisServices[service] ?? [], (item) {
+        buf.write('$item');
+      });
+    }
+
+    List<String> lines = (site as DiagnosticsSite).lastPrintedLines;
+    if (lines.isNotEmpty) {
+      h3('Debug output');
+      p(lines.join('\n'), style: 'white-space: pre');
+    }
+  }
+}
+
+class InstrumentationPage extends DiagnosticPageWithNav {
+  InstrumentationPage(DiagnosticsSite site)
+      : super(site, 'instrumentation', 'Instrumentation',
+            description:
+                'Verbose instrumentation data from the analysis server.');
+
+  @override
+  void generateContent(Map<String, String> params) {
+    p(
+        'Instrumentation can be enabled by starting the analysis server with the '
+        '<code>--instrumentation-log-file=path/to/file</code> flag.',
+        raw: true);
+
+    if (!AnalysisEngine.instance.instrumentationService.isActive) {
+      blankslate('Instrumentation not active.');
+      return;
+    }
+
+    h3('Instrumentation');
+
+    p('Instrumentation active.');
+
+    InstrumentationServer instrumentation =
+        AnalysisEngine.instance.instrumentationService.instrumentationServer;
+    String description = instrumentation.describe;
+    HtmlEscape htmlEscape = new HtmlEscape(HtmlEscapeMode.ELEMENT);
+    description = htmlEscape.convert(description);
+    // Convert http(s): references to hyperlinks.
+    final RegExp urlRegExp = new RegExp(r'[http|https]+:\/*(\S+)');
+    description = description.replaceAllMapped(urlRegExp, (Match match) {
+      return '<a href="${match.group(0)}">${match.group(1)}</a>';
+    });
+    p(description.replaceAll('\n', '<br>'), raw: true);
+  }
+}
+
+class ProfilePage extends DiagnosticPageWithNav {
+  ProfilePage(DiagnosticsSite site)
+      : super(site, 'profile', 'Profiling Info',
+            description: 'Profiling performance tag data.');
+
+  @override
+  void generateContent(Map<String, String> params) {
+    // prepare sorted tags
+    List<PerformanceTag> tags = PerformanceTag.all.toList();
+    tags.remove(ServerPerformanceStatistics.idle);
+    tags.removeWhere((tag) => tag.label == 'unknown');
+    tags.sort((a, b) => b.elapsedMs - a.elapsedMs);
+
+    // draw a pie chart
+    String rowData =
+        tags.map((tag) => "['${tag.label}', ${tag.elapsedMs}]").join(',');
+    buf.writeln(
+        '<div id="chart-div" style="width: 700px; height: 300px;"></div>');
+    buf.writeln('''
+      <script type="text/javascript">
+        google.charts.load('current', {'packages':['corechart']});
+        google.charts.setOnLoadCallback(drawChart);
+  
+        function drawChart() {
+          var data = new google.visualization.DataTable();
+          data.addColumn('string', 'Tag');
+          data.addColumn('number', 'Time (ms)');
+          data.addRows([$rowData]);
+          var options = {'title': 'Performance Tag Data', 'width': 700, 'height': 300};
+          var chart = new google.visualization.PieChart(document.getElementById('chart-div'));
+          chart.draw(data, options);
+        }
+      </script>    
+''');
+
+    // print total time
+    int totalTime =
+        tags.fold<int>(0, (int a, PerformanceTag tag) => a + tag.elapsedMs);
+    p('Total measured time: ${printMilliseconds(totalTime)}');
+
+    // write out a table
+    void _writeRow(List<String> data, {bool header: false}) {
+      buf.write('<tr>');
+      if (header) {
+        for (String d in data) {
+          buf.write('<th>$d</th>');
+        }
+      } else {
+        for (String d in data) {
+          buf.write('<td>$d</td>');
+        }
+      }
+      buf.writeln('</tr>');
+    }
+
+    buf.write('<table>');
+    _writeRow(['Tag name', 'Time (in ms)', 'Percent'], header: true);
+    void writeRow(PerformanceTag tag) {
+      double percent = tag.elapsedMs / totalTime;
+      _writeRow([
+        tag.label,
+        printMilliseconds(tag.elapsedMs),
+        printPercentage(percent)
+      ]);
+    }
+
+    tags.forEach(writeRow);
+    buf.write('</table>');
+  }
+}
+
+// TODO(devoncarew): This is not hooked up.
+class ExceptionsPage extends DiagnosticPageWithNav {
+  ExceptionsPage(DiagnosticsSite site)
+      : super(site, 'exceptions', 'Exceptions',
+            description: 'Exceptions from the analysis server.');
+
+  String get navDetail => exceptions.length.toString();
+
+  @override
+  void generateContent(Map<String, String> params) {
+    if (exceptions.isEmpty) {
+      blankslate('No exceptions encountered!');
+    } else {
+      for (CaughtException ex in exceptions) {
+        h3('${ex.exception}');
+        p(ex.toString(), style: 'white-space: pre');
+      }
+    }
+  }
+
+  // TODO: Implement - read this from a server exception ring buffer.
+  List<CaughtException> get exceptions => [];
+}
+
+class ContextsPage extends DiagnosticPageWithNav {
+  ContextsPage(DiagnosticsSite site)
+      : super(site, 'contexts', 'Contexts',
+            description:
+                'An analysis context defines the options and the set of sources being analyzed.');
+
+  String get navDetail => printInteger(server.driverMap.length);
+
+  @override
+  void generateContent(Map<String, String> params) {
+    Map<Folder, AnalysisDriver> driverMap = server.driverMap;
+    if (driverMap.isEmpty) {
+      blankslate('No contexts.');
+      return;
+    }
+
+    String contextPath = params['context'];
+    Folder folder = driverMap.keys
+        .firstWhere((f) => f.path == contextPath, orElse: () => null);
+
+    if (folder == null) {
+      folder = driverMap.keys.first;
+      contextPath = folder.path;
+    }
+
+    AnalysisDriver driver = driverMap[folder];
+
+    buf.writeln('<div class="tabnav">');
+    buf.writeln('<nav class="tabnav-tabs">');
+    for (Folder f in driverMap.keys) {
+      if (f == folder) {
+        buf.writeln(
+            '<a class="tabnav-tab selected">${escape(f.shortName)}</a>');
+      } else {
+        String p = '$path?context=${Uri.encodeQueryComponent(f.path)}';
+        buf.writeln(
+            '<a href="$p" class="tabnav-tab">${escape(f.shortName)}</a>');
+      }
+    }
+    buf.writeln('</nav>');
+    buf.writeln('</div>');
+
+    buf.writeln(writeOption('Context location', escape(contextPath)));
+    buf.writeln(writeOption('Analysis options path',
+        escape(driver.contextRoot.optionsFilePath ?? 'none')));
+
+    buf.writeln('<div class="columns">');
+
+    buf.writeln('<div class="column one-half">');
+    h3('Analysis options');
+    p(describe(driver.analysisOptions), raw: true);
+    buf.writeln(
+        writeOption('Has .packages file', folder.getChild('.packages').exists));
+    buf.writeln(writeOption(
+        'Has pubspec.yaml file', folder.getChild('pubspec.yaml').exists));
+    buf.writeln('</div>');
+
+    buf.writeln('<div class="column one-half">');
+    DartSdk sdk = driver?.sourceFactory?.dartSdk;
+    AnalysisOptionsImpl sdkOptions = sdk?.context?.analysisOptions;
+    if (sdkOptions != null) {
+      h3('SDK analysis options');
+      p(describe(sdkOptions), raw: true);
+
+      if (sdk is FolderBasedDartSdk) {
+        p(writeOption('Use summaries', sdk.useSummary), raw: true);
+      }
+    }
+    buf.writeln('</div>');
+
+    buf.writeln('</div>');
+
+    h3('Lints');
+    p(driver.analysisOptions.lintRules.map((l) => l.name).join(', '));
+
+    h3('Error processors');
+    p(driver.analysisOptions.errorProcessors
+        .map((e) => e.description)
+        .join(', '));
+
+    List<String> priorityFiles = driver.priorityFiles;
+    List<String> addedFiles = driver.addedFiles.toList();
+    List<String> implicitFiles =
+        driver.knownFiles.difference(driver.addedFiles).toList();
+    addedFiles.sort();
+    implicitFiles.sort();
+
+    String lenCounter(List list) {
+      return '<span class="counter" style="float: right;">${list.length}</span>';
+    }
+
+    h3('Context files');
+
+    h4('Priority files ${lenCounter(priorityFiles)}', raw: true);
+    inputList(priorityFiles, (file) => buf.write(file));
+
+    h4('Added files ${lenCounter(addedFiles)}', raw: true);
+    inputList(addedFiles, (file) => buf.write(file));
+
+    h4('ImplicitFiles files ${lenCounter(implicitFiles)}', raw: true);
+    inputList(implicitFiles, (file) => buf.write(file));
+
+    SourceFactory sourceFactory = driver.sourceFactory;
+    if (sourceFactory is SourceFactoryImpl) {
+      h3('Resolvers');
+      for (UriResolver resolver in sourceFactory.resolvers) {
+        h4(resolver.runtimeType.toString());
+        buf.write('<p>');
+        if (resolver is DartUriResolver) {
+          DartSdk sdk = resolver.dartSdk;
+          buf.write(' (sdk = ');
+          buf.write(sdk.runtimeType);
+          if (sdk is FolderBasedDartSdk) {
+            buf.write(' (path = ');
+            buf.write(sdk.directory.path);
+            buf.write(')');
+          } else if (sdk is EmbedderSdk) {
+            buf.write(' (map = ');
+            writeMap(sdk.urlMappings);
+            buf.write(')');
+          }
+          buf.write(')');
+        } else if (resolver is SdkExtUriResolver) {
+          buf.write(' (map = ');
+          writeMap(resolver.urlMappings);
+          buf.write(')');
+        } else if (resolver is PackageMapUriResolver) {
+          writeMap(resolver.packageMap);
+        }
+        buf.write('</p>');
+      }
+    }
+  }
+
+  String describe(AnalysisOptionsImpl options) {
+    StringBuffer b = new StringBuffer();
+
+    b.write(
+        writeOption('Analyze function bodies', options.analyzeFunctionBodies));
+    b.write(writeOption('Enable asserts in initializer lists',
+        options.enableAssertInitializer));
+    b.write(writeOption(
+        'Enable strict call checks', options.enableStrictCallChecks));
+    b.write(writeOption('Enable super mixins', options.enableSuperMixins));
+    b.write(writeOption('Generate dart2js hints', options.dart2jsHint));
+    b.write(writeOption(
+        'Generate errors in implicit files', options.generateImplicitErrors));
+    b.write(
+        writeOption('Generate errors in SDK files', options.generateSdkErrors));
+    b.write(writeOption('Generate hints', options.hint));
+    b.write(writeOption('Incremental resolution', options.incremental));
+    b.write(writeOption(
+        'Incremental resolution with API changes', options.incrementalApi));
+    b.write(writeOption('Preserve comments', options.preserveComments));
+    b.write(writeOption('Strong mode', options.strongMode));
+    b.write(writeOption('Strong mode hints', options.strongModeHints));
+
+    return b.toString();
+  }
+
+  void writeList<E>(List<E> list) {
+    buf.writeln('[${list.join(', ')}]');
+  }
+
+  void writeMap<V>(Map<String, V> map) {
+    List<String> keys = map.keys.toList();
+    keys.sort();
+    int length = keys.length;
+    buf.write('{');
+    for (int i = 0; i < length; i++) {
+      buf.write('<br>');
+      String key = keys[i];
+      V value = map[key];
+      buf.write(key);
+      buf.write(' = ');
+      if (value is List) {
+        writeList(value);
+      } else {
+        buf.write(value);
+      }
+      buf.write(',');
+    }
+    buf.write('<br>}');
+  }
+}
+
+class OverlaysPage extends DiagnosticPageWithNav {
+  OverlaysPage(DiagnosticsSite site)
+      : super(site, 'overlays', 'Overlays',
+            description: 'Editing overlays - unsaved file changes.');
+
+  @override
+  void generateContent(Map<String, String> params) {
+    FileContentOverlay overlays = server.fileContentOverlay;
+    List<String> paths = overlays.paths.toList()..sort();
+
+    String overlayPath = params['overlay'];
+    if (overlayPath != null) {
+      if (overlays[overlayPath] != null) {
+        buf.write('<pre><code>');
+        buf.write(overlays[overlayPath]);
+        buf.writeln('</code></pre>');
+      } else {
+        p('<code>${escape(overlayPath)}</code> not found.', raw: true);
+      }
+
+      return;
+    }
+
+    if (paths.isEmpty) {
+      blankslate('No overlays.');
+    } else {
+      String lenCounter(List list) {
+        return '<span class="counter" style="float: right;">${list.length}</span>';
+      }
+
+      h3('Overlays ${lenCounter(paths)}', raw: true);
+      ul(paths, (String overlayPath) {
+        String uri = '$path?overlay=${Uri.encodeQueryComponent(overlayPath)}';
+        buf.writeln('<a href="$uri">${escape(overlayPath)}</a>');
+      });
+    }
+  }
+}
+
+class PluginsPage extends DiagnosticPageWithNav {
+  PluginsPage(DiagnosticsSite site)
+      : super(site, 'plugins', 'Plugins', description: 'Plugins in use.');
+
+  @override
+  void generateContent(Map<String, String> params) {
+    h3('Analysis plugins');
+    List<PluginInfo> analysisPlugins = server.pluginManager.plugins;
+
+    if (analysisPlugins.isEmpty) {
+      blankslate('No analysis plugins active.');
+    } else {
+      ul(analysisPlugins, (PluginInfo p) {
+        buf.writeln('${p.data.name} ${p.pluginId} (${p.data.version})');
+      });
+    }
+
+    h3('Analyzer plugins');
+    void writePlugin(Plugin plugin) {
+      buf.write(plugin.uniqueIdentifier);
+      buf.write(' (');
+      buf.write(plugin.runtimeType);
+      buf.write(')');
+    }
+
+    List<Plugin> plugins = [
+      AnalysisEngine.instance.enginePlugin,
+      server.serverPlugin
+    ];
+    plugins.addAll(server.userDefinedPlugins);
+    ul(plugins, writePlugin);
+  }
+}
+
+class ExecutionDomainPage extends DiagnosticPageWithNav {
+  ExecutionDomainPage(DiagnosticsSite site)
+      : super(site, 'execution', 'Execution Domain',
+            description: 'Data for the analysis server\'s execution domain.');
+
+  @override
+  void generateContent(Map<String, String> params) {
+    ExecutionDomainHandler domain = server.handlers.firstWhere(
+        (handler) => handler is ExecutionDomainHandler,
+        orElse: () => null);
+
+    h3('Subscriptions');
+    ul(ExecutionService.VALUES, (item) {
+      if (domain.onFileAnalyzed != null) {
+        buf.write('$item (has subscriptions)');
+      } else {
+        buf.write('$item (no subscriptions)');
+      }
+    });
+  }
+}
+
+class CompletionPage extends DiagnosticPageWithNav {
+  CompletionPage(DiagnosticsSite site)
+      : super(site, 'completion', 'Code Completion',
+            description: 'Latency statistics for code completion.');
+
+  @override
+  void generateContent(Map<String, String> params) {
+    CompletionDomainHandler domain = server.handlers.firstWhere(
+        (handler) => handler is CompletionDomainHandler,
+        orElse: () => null);
+
+    List<CompletionPerformance> completions = domain.performanceList.toList();
+    completions.sort((a, b) => b.start.compareTo(a.start));
+
+    if (completions.isEmpty) {
+      blankslate('No completions recorded.');
+      return;
+    }
+
+    int fastCount =
+        completions.where((c) => c.elapsedInMilliseconds <= 100).length;
+    p('${completions.length} results; ${printPercentage(fastCount / completions.length)} within 100ms.');
+
+    // draw a chart
+    buf.writeln(
+        '<div id="chart-div" style="width: 700px; height: 300px;"></div>');
+    StringBuffer rowData = new StringBuffer();
+    for (int i = completions.length - 1; i >= 0; i--) {
+      // [' ', 101.5]
+      if (rowData.isNotEmpty) {
+        rowData.write(',');
+      }
+      rowData.write("[' ', ${completions[i].elapsedInMilliseconds}]");
+    }
+    buf.writeln('''
+      <script type="text/javascript">
+      google.charts.load('current', {'packages':['bar']});
+      google.charts.setOnLoadCallback(drawChart);
+      function drawChart() {
+        var data = google.visualization.arrayToDataTable([
+          ['Completions', 'Time'],
+          $rowData
+        ]);
+        var options = { bars: 'vertical', vAxis: {format: 'decimal'}, height: 300 };
+        var chart = new google.charts.Bar(document.getElementById('chart-div'));
+        chart.draw(data, google.charts.Bar.convertOptions(options));
+      }
+      </script>    
+''');
+
+    // emit the data as a table
+    buf.writeln('<table>');
+    buf.writeln(
+        '<tr><th>Time</th><th>Results</th><th>Source</th><th>Snippet</th></tr>');
+    for (CompletionPerformance completion in completions) {
+      buf.writeln('<tr>'
+          '<td class="pre right">${printMilliseconds(completion.elapsedInMilliseconds)}</td>'
+          '<td class="right">${completion.suggestionCount}</td>'
+          '<td>${escape(completion.source.shortName)}</td>'
+          '<td><code>${escape(completion.snippet)}</code></td>'
+          '</tr>');
+    }
+    buf.writeln('</table>');
+  }
+}
+
+// TODO(devoncarew): Show the last x requests and responses.
+class CommunicationsPage extends DiagnosticPageWithNav {
+  CommunicationsPage(DiagnosticsSite site)
+      : super(site, 'communications', 'Communications',
+            description:
+                'Latency statistics for analysis server communications.');
+
+  @override
+  void generateContent(Map<String, String> params) {
+    void writeRow(List<String> data, {List<String> classes}) {
+      buf.write("<tr>");
+      for (int i = 0; i < data.length; i++) {
+        String c = classes == null ? null : classes[i];
+        if (c != null) {
+          buf.write('<td class="$c">${escape(data[i])}</td>');
+        } else {
+          buf.write('<td>${escape(data[i])}</td>');
+        }
+      }
+      buf.writeln("</tr>");
+    }
+
+    buf.writeln('<div class="columns">');
+
+    ServerPerformance perf = server.performanceAfterStartup;
+    if (perf != null) {
+      buf.writeln('<div class="column one-half">');
+      h3('Current');
+
+      int requestCount = perf.requestCount;
+      double averageLatency =
+          requestCount > 0 ? (perf.requestLatency / requestCount) : 0.0;
+      int maximumLatency = perf.maxLatency;
+      double slowRequestPercent =
+          requestCount > 0 ? (perf.slowRequestCount / requestCount) : 0.0;
+
+      buf.write('<table>');
+      writeRow([printInteger(requestCount), 'requests'],
+          classes: ["right", null]);
+      writeRow([printMilliseconds(averageLatency), 'average latency'],
+          classes: ["right", null]);
+      writeRow([printMilliseconds(maximumLatency), 'maximum latency'],
+          classes: ["right", null]);
+      writeRow([printPercentage(slowRequestPercent), '> 150 ms latency'],
+          classes: ["right", null]);
+      buf.write('</table>');
+      buf.write('</div>');
+    }
+
+    buf.writeln('<div class="column one-half">');
+    h3('Startup');
+    perf = server.performanceDuringStartup;
+
+    int requestCount = perf.requestCount;
+    double averageLatency =
+        requestCount > 0 ? (perf.requestLatency / requestCount) : 0.0;
+    int maximumLatency = perf.maxLatency;
+    double slowRequestPercent =
+        requestCount > 0 ? (perf.slowRequestCount / requestCount) : 0.0;
+
+    buf.write('<table>');
+    writeRow([printInteger(requestCount), 'requests'],
+        classes: ["right", null]);
+    writeRow([printMilliseconds(averageLatency), 'average latency'],
+        classes: ["right", null]);
+    writeRow([printMilliseconds(maximumLatency), 'maximum latency'],
+        classes: ["right", null]);
+    writeRow([printPercentage(slowRequestPercent), '> 150 ms latency'],
+        classes: ["right", null]);
+    buf.write('</table>');
+
+    if (server.performanceAfterStartup != null) {
+      int startupTime =
+          server.performanceAfterStartup.startTime - perf.startTime;
+      p('(initial analysis time: ${printMilliseconds(startupTime)})');
+    }
+    buf.write('</div>');
+
+    buf.write('</div>');
+  }
+}
+
+String writeOption(String name, dynamic value) {
+  return '$name: <code>$value</code><br> ';
+}
+
+String get _sdkVersion {
+  String version = Platform.version;
+  if (version.contains(' ')) {
+    version = version.substring(0, version.indexOf(' '));
+  }
+  return version;
+}