feat: show DemoSource based on Vaadin version

Close #132

Author: javier-godoy

README.md

@@ -179,6 +179,16 @@ For instance, the following source would be rendered as `foo();` in Vaadin 23+,
 
 Strictly, the constructor of `SourceCodeViewer` receives a map with arbitrary variables defined by the caller, and `TabbedDemo` defines "vaadin" and "flow" variables. Implementation details in PR https://github.com/FlowingCode/CommonsDemo/pull/44.
 
+The `@DemoSource` annotation also supports a `condition` attribute to control the visibility of the source tab based on the environment. This feature uses the same syntax and operators as the conditional directives.
+
+
+```java
+@DemoSource(value = "/src/test/resources/META-INF/resources/frontend/example.css", condition = "vaadin ge 24")
+public class MyDemo extends Div {
+ ...
+}
+```
+
 ### Fragment highlighting 
 
 This feature supports highlighting a source code fragment in order to emphasize a section of the code snippet.

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

@@ -2,7 +2,7 @@
  * #%L
  * Commons Demo
  * %%
- * Copyright (C) 2020 - 2025 Flowing Code
+ * Copyright (C) 2020 - 2026 Flowing Code
  * %%
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -77,4 +77,6 @@
   /** Source code position in the layout */
   SourcePosition sourcePosition() default SourcePosition.SECONDARY;
 
+  String condition() default "";
+
 }

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

@@ -0,0 +1,93 @@
+/*-
+ * #%L
+ * Commons Demo
+ * %%
+ * Copyright (C) 2020 - 2026 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.demo;
+
+import java.util.Map;
+import lombok.NonNull;
+import lombok.experimental.UtilityClass;
+
+@UtilityClass
+class DemoSourceConditionHelper {
+
+  public boolean eval(String condition, Map<String, String> env) {
+    if (condition == null) {
+      return true;
+    }
+
+    String[] expr = condition.split(" ");
+
+    if (expr.length == 3) {
+      String lhs = env.get(expr[0]);
+
+      if (lhs == null) {
+        return false;
+      }
+
+      String operator = expr[1];
+      String rhs = expr[2];
+
+      switch (operator) {
+        case "lt":
+          return compare(lhs, rhs) < 0;
+        case "le":
+          return compare(lhs, rhs) <= 0;
+        case "eq":
+          return compare(lhs, rhs) == 0;
+        case "ge":
+          return compare(lhs, rhs) >= 0;
+        case "gt":
+          return compare(lhs, rhs) > 0;
+        case "ne":
+          return compare(lhs, rhs) != 0;
+        default:
+          throw new IllegalArgumentException("Unknown operator: " + operator);
+      }
+    } else {
+      throw new IllegalArgumentException("Invalid condition: '" + condition
+          + "'. Must be exactly 3 components: [VARIABLE] [OPERATOR] [VERSION]");
+    }
+  }
+
+  private int compare(String a, String b) {
+    String[] aa = split(a);
+    String[] bb = split(b);
+
+    int minLength = Math.min(aa.length, bb.length);
+
+    for (int i = 0; i < minLength; i++) {
+      int ai = Integer.parseInt(aa[i]);
+      int bi = Integer.parseInt(bb[i]);
+      int c = Integer.compare(ai, bi);
+      if (c != 0) {
+        return c;
+      }
+    }
+
+    return 0;
+  }
+
+  private String[] split(@NonNull String version) {
+    if (!version.matches("^\\d+(\\.\\d+){0,2}$")) {
+      throw new IllegalArgumentException("Invalid version: '" + version
+          + "'. Must be 'major', 'major.minor', or major.minor.patch'");
+    }
+    return version.split("\\.");
+  }
+}

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

@@ -2,7 +2,7 @@
  * #%L
  * Commons Demo
  * %%
- * Copyright (C) 2020 - 2025 Flowing Code
+ * Copyright (C) 2020 - 2026 Flowing Code
  * %%
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,6 +25,7 @@
 import com.vaadin.flow.component.html.Div;
 import com.vaadin.flow.component.tabs.Tab;
 import elemental.json.JsonValue;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -42,6 +43,12 @@ public class MultiSourceCodeViewer extends Div {
   private EnhancedTabs tabs;
 
   public MultiSourceCodeViewer(List<SourceCodeTab> sourceCodeTabs, Map<String, String> properties) {
+    sourceCodeTabs = new ArrayList<>(sourceCodeTabs);
+    sourceCodeTabs.removeIf(tab -> !DemoSourceConditionHelper.eval(tab.getCondition(), properties));
+    if (sourceCodeTabs.isEmpty()) {
+      return;
+    }
+
     if (sourceCodeTabs.size() > 1) {
       tabs = new EnhancedTabs(createTabs(sourceCodeTabs));
       tabs.addSelectedChangeListener(ev -> onTabSelected(ev.getSelectedTab()));
@@ -69,6 +76,10 @@ public MultiSourceCodeViewer(List<SourceCodeTab> sourceCodeTabs, Map<String, Str
     getStyle().set("flex-direction", "column");
   }
 
+  public boolean isEmpty() {
+    return selectedTab == null;
+  }
+
   private Tab[] createTabs(List<SourceCodeTab> sourceCodeTabs) {
     return sourceCodeTabs.stream().map(this::createTab).toArray(Tab[]::new);
   }
@@ -134,7 +145,12 @@ private void fetchContents(String url, String language) {
   }
 
   public SourcePosition getSourcePosition() {
-    return (SourcePosition) ComponentUtil.getData(selectedTab, DATA_POSITION);
+    if (selectedTab != null) {
+      return (SourcePosition) ComponentUtil.getData(selectedTab, DATA_POSITION);
+    } else {
+      return SourcePosition.SECONDARY;
+    }
+
   }
 
   private Optional<Tab> findTabWithFilename(String filename) {

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

@@ -2,7 +2,7 @@
  * #%L
  * Commons Demo
  * %%
- * Copyright (C) 2020 - 2024 Flowing Code
+ * Copyright (C) 2020 - 2026 Flowing Code
  * %%
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,6 +36,7 @@ public class SourceCodeTab {
   private final String url;
   private String caption;
   private String language;
+  private String condition;
   @NonNull
   private final SourcePosition sourcePosition;
 

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

@@ -2,7 +2,7 @@
  * #%L
  * Commons Demo
  * %%
- * Copyright (C) 2020 - 2023 Flowing Code
+ * Copyright (C) 2020 - 2026 Flowing Code
  * %%
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -54,6 +54,10 @@ public SplitLayoutDemo(Component demo, List<SourceCodeTab> tabs) {
     getContent().setSizeFull();
   }
 
+  public boolean isEmpty() {
+    return code.isEmpty();
+  }
+
   private void setSourcePosition(SourcePosition position) {
     if (!position.equals(sourcePosition)) {
       getContent().removeAll();

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

@@ -2,7 +2,7 @@
  * #%L
  * Commons Demo
  * %%
- * Copyright (C) 2020 - 2025 Flowing Code
+ * Copyright (C) 2020 - 2026 Flowing Code
  * %%
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -181,16 +181,21 @@ public void showRouterLayoutContent(HasElement content) {
     }
 
     if (!sourceTabs.isEmpty()) {
-      content = new SplitLayoutDemo(demo, sourceTabs);
-      currentLayout = (SplitLayoutDemo) content;
+      currentLayout = new SplitLayoutDemo(demo, sourceTabs);
+      if (currentLayout.isEmpty()) {
+        demo.getElement().removeAttribute("slot");
+        currentLayout = null;
+      }
+    }
+
+    if (currentLayout != null) {
+      content = currentLayout;
       if (splitOrientation != null) {
         setOrientation(splitOrientation);
         updateSplitterPosition();
       }
 
-      if (currentLayout != null) {
-        setupDemoHelperButton(currentLayout.getContent().getPrimaryComponent().getClass());
-      }
+      setupDemoHelperButton(currentLayout.getContent().getPrimaryComponent().getClass());
     } else {
       currentLayout = null;
       demo.getElement().getStyle().set("height", "100%");
@@ -245,6 +250,10 @@ private Optional<SourceCodeTab> createSourceCodeTab(Class<?> annotatedClass, Dem
       builder.language(annotation.caption());
     }
 
+    if (!annotation.condition().isEmpty()) {
+      builder.condition(annotation.condition());
+    }
+
     builder.sourcePosition(annotation.sourcePosition());
 
     return Optional.of(builder.build());

src/test/java/com/flowingcode/vaadin/addons/demo/MultiSourceDemo.java

@@ -1,7 +1,7 @@
 /*-
  * #%L
  * %%
- * Copyright (C) 2020 - 2024 Flowing Code
+ * Copyright (C) 2020 - 2026 Flowing Code
  * %%
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,9 +29,13 @@
 // show-source @DemoSource
 // show-source @DemoSource(clazz = AdditionalSources.class)
 // show-source @DemoSource("/src/test/resources/META-INF/resources/frontend/multi-source-demo.css")
+// show-source @DemoSource(value="/src/test/resources/META-INF/resources/frontend/condition-true.css", condition = "vaadin ge 14")
+// show-source @DemoSource(value="/src/test/resources/META-INF/resources/frontend/condition-false.css", condition = "vaadin eq 0")
 @DemoSource
 @DemoSource(clazz = AdditionalSources.class)
 @DemoSource("/src/test/resources/META-INF/resources/frontend/multi-source-demo.css")
+@DemoSource(value="/src/test/resources/META-INF/resources/frontend/condition-true.css", condition = "vaadin ge 14")
+@DemoSource(value="/src/test/resources/META-INF/resources/frontend/condition-false.css", condition = "vaadin eq 0")
 @StyleSheet("./multi-source-demo.css")
 public class MultiSourceDemo extends Div {
   public MultiSourceDemo() {

src/test/resources/META-INF/resources/frontend/condition-false.css

@@ -0,0 +1 @@
+/** This source file is conditionally hidden. */

src/test/resources/META-INF/resources/frontend/condition-true.css

@@ -0,0 +1 @@
+/** This source is shown when Vaadin version is 14+ */