Refactor dartdoc into a class. Use method overriding to extend.

client/html/scripts/html_doc.dart

 // Copyright (c) 2011, 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 script to document the HTML library, including annotations on the mapping
  * to and from the DOM library. To use it, from utils/dartdoc, run:
  *
  *     $ htmldoc
  *
  * This works just like `dartdoc html`, with the additions of the DOM/HTML
  * mapping documentation.
  */
 #library('html_doc');
 
 #import('html_diff.dart');
 #import('../../../frog/lang.dart');
 #import('../../../frog/file_system_node.dart');
 #import('../../../frog/file_system.dart');
 #import('../../../utils/dartdoc/dartdoc.dart', prefix: 'doc');
 
 HtmlDiff _diff;
 
 void main() {
   var files = new NodeFileSystem();
   parseOptions('../../frog', [] /* args */, files);
   initializeWorld(files);
-  doc.initializeDartDoc();
+  final htmldoc = new Htmldoc();
   HtmlDiff.initialize();
 
   _diff = new HtmlDiff();
   _diff.run();
   world.reset();
 
-  doc.addMethodDocumenter(addMemberDoc);
-  doc.addFieldDocumenter(addMemberDoc);
-  doc.addTypeDocumenter(addTypeDoc);
-  doc.document('html');
+  htmldoc.document('html');
+}
+
+class Htmldoc extends doc.Dartdoc {
+  getTypeComment(Type type) {
+    return _mergeComments(super.getTypeComment(type), getTypeDoc(type));
+  }
+
+  getMethodComment(MethodMember method) {
+    return _mergeComments(super.getMethodComment(method), getMemberDoc(method));
+  }
+
+  getFieldComment(FieldMember field) {
+    return _mergeComments(super.getFieldComment(field), getMemberDoc(field));
+  }
+
+  String _mergeComments(String comment, String extra) {
+    if (comment == null) return extra;
+    return '$comment\n\n$extra';
+  }
 }
 
 /**
  * Returns a Markdown-formatted link to [member], relative to a type page that
  * may be in a different library than [member].
  */
 String _linkMember(Member member) {
   final typeName = member.declaringType.name;
   var memberName = "$typeName.${member.name}";
   if (member.isConstructor || member.isFactory) {
@@ skipping 25 matching lines @@
     var getName = m.name.replaceFirst('set:', 'get:');
     return !members.some((maybeGet) => maybeGet.name == getName);
   });
 }
 
 /**
  * Returns additional Markdown-formatted documentation for [member], linking it
  * to the corresponding `dart:html` or `dart:dom` [Member](s). If [member] is
  * not in `dart:html` or `dart:dom`, returns no additional documentation.
  */
-String addMemberDoc(Member member) {
+String getMemberDoc(Member member) {
   if (_diff.domToHtml.containsKey(member)) {
     final htmlMemberSet = _unifyProperties(_diff.domToHtml[member]);
     final allSameName = htmlMemberSet.every((m) => _diff.sameName(member, m));
     final phrase = allSameName ? "available as" : "renamed to";
     final htmlMembers = doc.joinWithCommas(map(htmlMemberSet, _linkMember));
     return "_This is $phrase $htmlMembers in the " +
       "[dart:html](../html.html) library._";
   } else if (_diff.htmlToDom.containsKey(member)) {
     final domMemberSet = _unifyProperties(_diff.htmlToDom[member]);
     final allSameName = domMemberSet.every((m) => _diff.sameName(m, member));
     final phrase = allSameName ? "is the same as" : "renames";
     final domMembers = doc.joinWithCommas(map(domMemberSet, _linkMember));
     return "_This $phrase $domMembers in the [dart:dom](../dom.html) " +
       "library._";
   } else {
     return "";
   }
 }
 
 /**
  * Returns additional Markdown-formatted documentation for [type], linking it to
  * the corresponding `dart:html` or `dart:dom` [Type](s). If [type] is not in
  * `dart:html` or `dart:dom`, returns no additional documentation.
  */
-String addTypeDoc(Type type) {
+String getTypeDoc(Type type) {
   if (_diff.domTypesToHtml.containsKey(type)) {
     var htmlTypes = doc.joinWithCommas(
         map(_diff.domTypesToHtml[type], _linkType));
     return "_This corresponds to $htmlTypes in the [dart:html](../html.html) " +
       "library._";
   } else if (_diff.htmlTypesToDom.containsKey(type)) {
     var domTypes = doc.joinWithCommas(
         map(_diff.htmlTypesToDom[type], _linkType));
     return "_This corresponds to $domTypes in the [dart:dom](../dom.html) " +
       "library._";
   } else {
     return "";
   }
 }