Display 'Available extensions' in more, correct, places (#3852)

We weren't displaying them on enums, mixins, or extension types.

Also fixed some capitalization, and margins.

Author: srawlins

lib/resources/styles.css

@@ -661,6 +661,7 @@ footer a, footer a:hover {
 }
 
 .markdown.desc {
+  margin-bottom: 1em;
   max-width: 700px;
 }
 

lib/src/generator/templates.aot_renderers_for_html.dart

@@ -0,0 +1,8 @@
+{{ #hasPotentiallyApplicableExtensions }}
+  <dt>Available extensions</dt>
+  <dd><ul class="comma-separated clazz-relationships">
+    {{ #potentiallyApplicableExtensionsSorted }}
+      <li>{{{ linkedName }}}</li>
+    {{ /potentiallyApplicableExtensionsSorted }}
+  </ul></dd>
+{{ /hasPotentiallyApplicableExtensions }}

lib/templates/_available_extensions.html

@@ -1,5 +1,5 @@
 {{ #hasPublicMixedInTypes }}
-  <dt>Mixed in types</dt>
+  <dt>Mixed-in types</dt>
   <dd>
     <ul class="comma-separated {{ relationshipsClass }}">
       {{ #publicMixedInTypes }}

lib/templates/_mixed_in_types.html

@@ -28,15 +28,7 @@
           </ul></dd>
         {{ /hasPublicImplementers }}
 
-        {{ #hasPotentiallyApplicableExtensions }}
-          <dt>Available Extensions</dt>
-          <dd><ul class="comma-separated clazz-relationships">
-            {{ #potentiallyApplicableExtensionsSorted }}
-              <li>{{{ linkedName }}}</li>
-            {{ /potentiallyApplicableExtensionsSorted }}
-          </ul></dd>
-        {{ /hasPotentiallyApplicableExtensions }}
-
+        {{ >available_extensions }}
         {{ >container_annotations }}
       </dl>
     </section>

lib/templates/class.html

@@ -23,6 +23,7 @@ <h1>
           {{ >super_chain }}
           {{ >interfaces }}
           {{ >mixed_in_types }}
+          {{ >available_extensions }}
           {{ >container_annotations }}
         </dl>
       </section>

lib/templates/enum.html

@@ -31,6 +31,7 @@
             {{ /publicImplementersSorted }}
           </ul></dd>
         {{ /hasPublicImplementers }}
+        {{ >available_extensions }}
       </dl>
       {{ >container_annotations }}
     </section>

lib/templates/extension_type.html

@@ -16,7 +16,7 @@
       <section>
         <dl class="dl-horizontal">
           {{ #hasPublicSuperclassConstraints }}
-            <dt>Superclass Constraints</dt>
+            <dt>Superclass constraints</dt>
             <dd><ul class="comma-separated dark mixin-relationships">
               {{ #publicSuperclassConstraints }}
                 <li>{{{ linkedName }}}</li>
@@ -28,7 +28,7 @@
           {{ >interfaces }}
 
           {{ #hasPublicImplementers }}
-            <dt>Mixin Applications</dt>
+            <dt>Mixin applications</dt>
             <dd>
               <ul class="comma-separated mixin-relationships">
                 {{ #publicImplementersSorted }}
@@ -37,6 +37,7 @@
               </ul>
             </dd>
           {{ /hasPublicImplementers }}
+          {{ >available_extensions }}
 
           {{ >annotations }}
         </dl>

lib/templates/mixin.html

@@ -149,6 +149,21 @@ mixin M on _M {}
     ]);
   }
 
+  void test_availableExtensions_direct() async {
+    await createPackageWithLibrary('''
+class C {}
+extension E on C {}
+''');
+    var baseLines = readLines(['lib', 'C-class.html']);
+
+    baseLines.expectMainContentContainsAllInOrder([
+      matches('<dt>Available extensions</dt>'),
+      matches('<dd><ul class="comma-separated clazz-relationships">'),
+      matches('<li><a href="../lib/E.html">E</a></li>'),
+      matches('</ul></dd>'),
+    ]);
+  }
+
   void test_constructor_named() async {
     await createPackageWithLibrary('''
 class C {

test/templates/class_test.dart

@@ -91,6 +91,8 @@ enum EnumWithDefaultConstructor {
   /// Doc comment for [six].
   six;
 }
+
+extension Ext<T> on E<T> {}
 '''),
         ],
         resourceProvider: resourceProvider,
@@ -158,13 +160,22 @@ enum EnumWithDefaultConstructor {
       expect(
           eLines,
           containsAllInOrder([
-            matches('<dt>Mixed in types</dt>'),
+            matches('<dt>Mixed-in types</dt>'),
             matches('<a href="../lib/M-mixin.html">M</a>'
                 '<span class="signature">&lt;<wbr>'
                 '<span class="type-parameter">T</span>&gt;</span>'),
           ]));
     });
 
+    test('enum page contains available extensions', () async {
+      expect(
+          eLines,
+          containsAllInOrder([
+            matches('<dt>Available extensions</dt>'),
+            matches('<a href="../lib/E.html">E</a></span>'),
+          ]));
+    });
+
     test('enum page contains annotations', () async {
       eLines.expectMainContentContainsAllInOrder([
         matches('<dt>Annotations</dt>'),