feat: allow linking to demo snippets in branch

Close #34

Author: javier-godoy

src/main/java/com/flowingcode/vaadin/addons/GithubBranch.java

@@ -0,0 +1,44 @@
+/*-
+ * #%L
+ * Commons Demo
+ * %%
+ * Copyright (C) 2020 - 2022 Flowing Code
+ * %%
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * #L%
+ */
+package com.flowingcode.vaadin.addons;
+
+import com.flowingcode.vaadin.addons.demo.DemoSource;
+import com.flowingcode.vaadin.addons.demo.TabbedDemo;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * This annotation is used for configuring the default branch for {@link TabbedDemo} code snippets.
+ *
+ * The annotation can be placed in either the demo class or its containing package. Class-level
+ * annotations take precedence over package level annotations.
+ *
+ * @author Javier Godoy / Flowing Code
+ * @see DemoSource
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.TYPE, ElementType.PACKAGE})
+@Inherited
+public @interface GithubBranch {
+  String value();
+}

src/main/java/com/flowingcode/vaadin/addons/demo/DemoSource.java

@@ -19,16 +19,21 @@
  */
 package com.flowingcode.vaadin.addons.demo;
 
+import com.flowingcode.vaadin.addons.GithubBranch;
+import com.flowingcode.vaadin.addons.GithubLink;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
  * This annotation is used for configuring the source code URL in a {@link TabbedDemo}. If no {@code
- * value} is specified, and the demo view is annotated with {@link @GithubLink}, the source URL
- * defaults to the location of the annotated class under {@code src/java/test} in the master branch
- * of the repository.
+ * value} is specified, and the demo view is annotated with {@link GithubLink}, then the source URL
+ * defaults to the location of the annotated class under {@code src/java/test} and the branch is
+ * determined from the value of {@link GithubBranch} in the demo view class (if the annotation is
+ * present) or the containing package of the demo view class. If the source URL is defaulted and no
+ * {@code GithubBranch} annotation is present either in the demo view class or its containing
+ * package, then the branch defaults to {@code master}.
  *
  * @author Javier Godoy / Flowing Code
  */

src/main/java/com/flowingcode/vaadin/addons/demo/TabbedDemo.java

@@ -19,6 +19,7 @@
  */
 package com.flowingcode.vaadin.addons.demo;
 
+import com.flowingcode.vaadin.addons.GithubBranch;
 import com.flowingcode.vaadin.addons.GithubLink;
 import com.vaadin.flow.component.AttachEvent;
 import com.vaadin.flow.component.Component;
@@ -185,9 +186,11 @@ public void showRouterLayoutContent(HasElement content) {
     if (demoSource != null) {
       sourceCodeUrl = demoSource.value();
       if (sourceCodeUrl.equals(DemoSource.GITHUB_SOURCE)) {
+        String branch = lookupGithubBranch(this.getClass());
+        String demoFile = demo.getClass().getName().replace('.', '/');
         sourceCodeUrl = Optional.ofNullable(this.getClass().getAnnotation(GithubLink.class))
-            .map(githubLink -> githubLink.value() + "/blob/master/src/test/java/"
-                + demo.getClass().getName().replace('.', '/') + ".java")
+            .map(githubLink -> String.format("%s/blob/%s/src/test/java/%s.java", githubLink.value(),
+                branch, demoFile))
             .orElse(null);
       }
       content = new SplitLayoutDemo(demo, sourceCodeUrl);
@@ -209,6 +212,17 @@ public void showRouterLayoutContent(HasElement content) {
     getElement().insertChild(1, content.getElement());
   }
 
+  private String lookupGithubBranch(Class<? extends TabbedDemo> clazz) {
+    GithubBranch branch = clazz.getAnnotation(GithubBranch.class);
+    if (branch == null) {
+      Package pkg = clazz.getPackage();
+      if (pkg!=null) {
+        branch = pkg.getAnnotation(GithubBranch.class);
+      }
+    }
+    return Optional.ofNullable(branch).map(GithubBranch::value).orElse("master");
+  }
+
   @Override
   public void removeRouterLayoutContent(HasElement oldContent) {
     getElement().removeChild(1);