Fix rel canonical link

Author: jdkoren

lib/src/html/template_data.dart

@@ -2,7 +2,6 @@
 // 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 'package:dartdoc/src/render/template_renderer.dart';
 import 'package:dartdoc/src/model/model.dart';
 
 abstract class HtmlOptions {
@@ -40,6 +39,13 @@ abstract class TemplateData<T extends Documentable> {
   String get relCanonicalPrefix => htmlOptions.relCanonicalPrefix;
   bool get useBaseHref => htmlOptions.useBaseHref;
 
+  String get bareHref {
+    if (self is Indexable) {
+      return (self as Indexable).href.replaceAll(HTMLBASE_PLACEHOLDER, '');
+    }
+    return '';
+  }
+
   String _layoutTitle(String name, String kind, bool isDeprecated) =>
       packageGraph.rendererFactory.templateRenderer
           .composeLayoutTitle(name, kind, isDeprecated);

lib/templates/_head.html

@@ -10,7 +10,7 @@
   <meta name="description" content="{{ metaDescription }}">
   <title>{{ title }}</title>
   {{ #relCanonicalPrefix }}
-  <link rel="canonical" href="{{{relCanonicalPrefix}}}/{{{self.href}}}">
+  <link rel="canonical" href="{{{relCanonicalPrefix}}}/{{{bareHref}}}">
   {{ /relCanonicalPrefix}}
 
   {{#useBaseHref}}{{! TODO(jdkoren): remove when the useBaseHref option is removed.}}

test/dartdoc_test.dart

@@ -406,5 +406,19 @@ void main() {
         expect(e is DartdocFailure, isTrue);
       }
     });
+
+    test('rel canonical prefix does not include base href', () async {
+      final String prefix = 'foo.bar/baz';
+      Dartdoc dartdoc = await buildDartdoc(
+          ['--rel-canonical-prefix', prefix], testPackageMinimumDir, tempDir);
+      await dartdoc.generateDocsBase();
+
+      File file = File(path.join(tempDir.path, 'small', 'small-library.html'));
+      expect(file.existsSync(), isTrue);
+      expect(
+          file.readAsStringSync(),
+          contains(
+              '<link rel="canonical" href="$prefix/small/small-library.html">'));
+    });
   }, timeout: Timeout.factor(8));
 }