godoc: list examples in index

Fixes #2897.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5658047

doc/godocs.js

@@ -23,7 +23,7 @@ bindEvent(window, 'load', godocs_onload);
 function godocs_onload() {
   godocs_bindSearchEvents();
   godocs_generateTOC();
-  godocs_bindExampleToggles();
+  godocs_bindExamples();
 }
 
 function godocs_bindSearchEvents() {
@@ -158,11 +158,14 @@ function godocs_nodeToText(node) {
   return text;
 }
 
-function godocs_bindExampleToggles() {
+function godocs_bindExamples() {
   var examples = document.getElementsByClassName("example");
   for (var i = 0; i < examples.length; i++) {
-    var eg = examples[i];
-    godocs_bindExampleToggle(eg);
+    godocs_bindExampleToggle(examples[i]);
+  }
+  var links = document.getElementsByClassName("exampleLink");
+  for (var i = 0; i < links.length; i++) {
+    godocs_bindExampleLink(links[i]);
   }
 }
 function godocs_bindExampleToggle(eg) {
@@ -177,3 +180,14 @@ function godocs_bindExampleToggle(eg) {
     });
   }
 }
+function godocs_bindExampleLink(l) {
+  var prefix = "example_";
+  bindEvent(l, "click", function() {
+    var i = l.href.indexOf("#"+prefix);
+    if (i < 0)
+      return;
+    var id = prefix + l.href.slice(i+1+prefix.length);
+    var eg = document.getElementById(id);
+    eg.className = "exampleVisible";
+  });
+}

lib/godoc/example.html

-<div class="example">
+<div id="example_{{.Name}}" class="example">
 	<div class="collapsed">
 		<p class="exampleHeading">▹ Example</p>
 	</div>

lib/godoc/package.html

@@ -52,6 +52,15 @@
 			{{end}}
 		</dl>
 
+		{{if $.Examples}}
+			<h4>Examples</h4>
+			<dl>
+			{{range $.Examples}}
+			<dd><a class="exampleLink" href="#example_{{.Name}}">{{.Name}}</a></dd>
+			{{end}}
+			</dl>
+		{{end}}
+
 		{{with .Filenames}}
 			<h4>Package files</h4>
 			<p>

src/cmd/godoc/godoc.go

@@ -522,8 +522,8 @@ func example_htmlFunc(funcName string, examples []*doc.Example, fset *token.File
 		code = code[2 : len(code)-2]
 
 		err := exampleHTML.Execute(&buf, struct {
-			Code, Output string
-		}{code, eg.Output})
+			Name, Code, Output string
+		}{name, code, eg.Output})
 		if err != nil {
 			log.Print(err)
 		}