fix: implement specific interfaces in ElementalNode classes

pom.xml

@@ -136,6 +136,30 @@
         </pluginManagement>
 
         <plugins>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>3.1.0</version>
+                <executions>
+                    <execution>
+                        <phase>process-classes</phase>
+                        <goals>
+                            <goal>java</goal>
+                        </goals>
+                        <configuration>
+                            <mainClass>com.flowingcode.vaadin.jsonmigration.ElementalNodeAsmPostProcessor</mainClass>
+                            <arguments>
+                                <argument>${project.build.outputDirectory}/com/flowingcode/vaadin/jsonmigration/ElementalArrayNode.class</argument>
+                                <argument>${project.build.outputDirectory}/com/flowingcode/vaadin/jsonmigration/ElementalBooleanNode.class</argument>
+                                <argument>${project.build.outputDirectory}/com/flowingcode/vaadin/jsonmigration/ElementalNullNode.class</argument>
+                                <argument>${project.build.outputDirectory}/com/flowingcode/vaadin/jsonmigration/ElementalNumberNode.class</argument>
+                                <argument>${project.build.outputDirectory}/com/flowingcode/vaadin/jsonmigration/ElementalObjectNode.class</argument>
+                                <argument>${project.build.outputDirectory}/com/flowingcode/vaadin/jsonmigration/ElementalStringNode.class</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-jar-plugin</artifactId>
@@ -216,6 +240,9 @@
                             <quiet>true</quiet>
                             <doclint>none</doclint>
 							<failOnWarnings>true</failOnWarnings>
+                            <sourceFileExcludes>
+                                <sourceFileExclude>**/ElementalNodeAsmPostProcessor.java</sourceFileExclude>
+                            </sourceFileExcludes>
                             <links>
                                 <link>https://javadoc.io/doc/com.vaadin/vaadin-platform-javadoc/${vaadin.version}</link>								
                             </links>
@@ -229,6 +256,8 @@
                             <!-- Generated file that shouldn't be included in add-ons -->
                             <excludes>
                                 <exclude>META-INF/VAADIN/config/flow-build-info.json</exclude>
+                                <exclude>com/flowingcode/vaadin/jsonmigration/ElementalNodeAsmPostProcessor.class</exclude>
+                                <exclude>com/flowingcode/vaadin/jsonmigration/ElementalNodeAsmPostProcessor$*.class</exclude>
                             </excludes>
                         </configuration>
                     </plugin>

src/main/java/com/flowingcode/vaadin/jsonmigration/ElementalArrayNode.java

@@ -2,7 +2,7 @@
  * #%L
  * Json Migration Helper
  * %%
- * Copyright (C) 2025 Flowing Code
+ * Copyright (C) 2025 - 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.
@@ -29,7 +29,7 @@
 import tools.jackson.databind.node.JsonNodeFactory;
 
 @SuppressWarnings("serial")
-class ElementalArrayNode extends ArrayNode implements UnsupportedJsonValueImpl {
+class ElementalArrayNode extends ArrayNode implements UnsupportedJsonValueImpl<JsonArray> {
 
   public ElementalArrayNode(JsonArray a) {
     super(JsonNodeFactory.instance, children(a));

src/main/java/com/flowingcode/vaadin/jsonmigration/ElementalBooleanNode.java

@@ -2,7 +2,7 @@
  * #%L
  * Json Migration Helper
  * %%
- * Copyright (C) 2025 Flowing Code
+ * Copyright (C) 2025 - 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.
@@ -19,11 +19,12 @@
  */
 package com.flowingcode.vaadin.jsonmigration;
 
+import elemental.json.JsonBoolean;
 import elemental.json.JsonType;
 import tools.jackson.databind.node.BooleanNode;
 
 @SuppressWarnings("serial")
-class ElementalBooleanNode extends BooleanNode implements UnsupportedJsonValueImpl {
+class ElementalBooleanNode extends BooleanNode implements UnsupportedJsonValueImpl<JsonBoolean> {
 
   public ElementalBooleanNode(boolean value) {
     super(value);

src/main/java/com/flowingcode/vaadin/jsonmigration/ElementalNodeAsmPostProcessor.java

@@ -0,0 +1,139 @@
+/*-
+ * #%L
+ * Json Migration Helper
+ * %%
+ * Copyright (C) 2025 - 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.jsonmigration;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.Optional;
+import lombok.NonNull;
+import lombok.SneakyThrows;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.Type;
+import org.objectweb.asm.signature.SignatureReader;
+import org.objectweb.asm.signature.SignatureVisitor;
+
+/**
+ * Dynamically modifies the class header to implement the JSON interface specified in the
+ * UnsupportedJsonValueImpl<T> generic argument.
+ */
+public class ElementalNodeAsmPostProcessor {
+
+  public static void main(String[] args) throws Exception {
+    for (String arg : args) {
+      Path classPath = Paths.get(arg);
+      byte[] b = Files.readAllBytes(classPath);
+
+      ClassReader cr = new ClassReader(b);
+      ClassWriter cw = new ClassWriter(cr, 0);
+      ClassVisitorImpl transformer = new ClassVisitorImpl(cw);
+
+      cr.accept(transformer, 0);
+
+      if (transformer.modified) {
+        Files.write(classPath, cw.toByteArray());
+        System.out.println("Successfully patched: " + classPath.getFileName());
+      }
+    }
+  }
+
+  private static class ClassVisitorImpl extends ClassVisitor {
+
+    private final static String TARGET_INTERFACE =
+        Type.getInternalName(UnsupportedJsonValueImpl.class);
+
+    boolean modified;
+
+    public ClassVisitorImpl(ClassVisitor cv) {
+      super(Opcodes.ASM9, cv);
+    }
+
+    @Override
+    @SneakyThrows
+    public void visit(int version, int access, String name, String signature, String superName,
+        String[] interfaces) {
+      String detectedInterface = detectInterface(signature);
+
+      for (String intf : interfaces) {
+        if (intf.equals(detectedInterface)) {
+          return;
+        }
+      }
+
+      modified = true;
+      interfaces = Arrays.copyOf(interfaces, interfaces.length + 1);
+      interfaces[interfaces.length - 1] = detectedInterface;
+      super.visit(version, access, name, signature, superName, interfaces);
+    }
+
+    private String detectInterface(@NonNull String signature) {
+      // Extracts the internal name of the specific generic type argument 'T' from
+      // the class signature implementing UnsupportedJsonValueImpl<T>.
+      String[] detectedInterface = new String[1];
+      SignatureReader reader = new SignatureReader(signature);
+      reader.accept(new SignatureVisitor(Opcodes.ASM9) {
+        private boolean insideTargetInterface = false;
+
+        @Override
+        public SignatureVisitor visitTypeArgument(char wildcard) {
+          // Move into the <T> block
+          return super.visitTypeArgument(wildcard);
+        }
+
+        @Override
+        public SignatureVisitor visitInterface() {
+          return this;
+        }
+
+        @Override
+        public void visitClassType(String name) {
+          if (name.equals(TARGET_INTERFACE)) {
+            insideTargetInterface = true;
+          } else if (insideTargetInterface && detectedInterface[0] == null) {
+            // This is the first class type found AFTER UnsupportedJsonValueImpl
+            // which represents the generic argument T
+            detectedInterface[0] = name;
+            insideTargetInterface = false; // Stop looking
+          }
+        }
+
+        @Override
+        public void visitEnd() {
+          insideTargetInterface = false;
+          super.visitEnd();
+        }
+
+      });
+      return Optional.ofNullable(detectedInterface[0])
+          .orElseThrow(() -> new IllegalArgumentException("Failed to extract interface"));
+    }
+
+    @Override
+    public void visitEnd() {
+      super.visitEnd();
+    }
+
+  }
+
+}

src/main/java/com/flowingcode/vaadin/jsonmigration/ElementalNullNode.java

@@ -2,7 +2,7 @@
  * #%L
  * Json Migration Helper
  * %%
- * Copyright (C) 2025 Flowing Code
+ * Copyright (C) 2025 - 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.
@@ -19,11 +19,12 @@
  */
 package com.flowingcode.vaadin.jsonmigration;
 
+import elemental.json.JsonNull;
 import elemental.json.JsonType;
 import tools.jackson.databind.node.NullNode;
 
 @SuppressWarnings("serial")
-class ElementalNullNode extends NullNode implements UnsupportedJsonValueImpl {
+class ElementalNullNode extends NullNode implements UnsupportedJsonValueImpl<JsonNull> {
 
   public ElementalNullNode() {
     super();

src/main/java/com/flowingcode/vaadin/jsonmigration/ElementalNumberNode.java

@@ -2,7 +2,7 @@
  * #%L
  * Json Migration Helper
  * %%
- * Copyright (C) 2025 Flowing Code
+ * Copyright (C) 2025 - 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.
@@ -19,11 +19,12 @@
  */
 package com.flowingcode.vaadin.jsonmigration;
 
+import elemental.json.JsonNumber;
 import elemental.json.JsonType;
 import tools.jackson.databind.node.DoubleNode;
 
 @SuppressWarnings("serial")
-class ElementalNumberNode extends DoubleNode implements UnsupportedJsonValueImpl {
+class ElementalNumberNode extends DoubleNode implements UnsupportedJsonValueImpl<JsonNumber> {
 
   public ElementalNumberNode(double value) {
     super(value);

src/main/java/com/flowingcode/vaadin/jsonmigration/ElementalObjectNode.java

@@ -2,7 +2,7 @@
  * #%L
  * Json Migration Helper
  * %%
- * Copyright (C) 2025 Flowing Code
+ * Copyright (C) 2025 - 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.
@@ -31,7 +31,7 @@
 import tools.jackson.databind.node.ObjectNode;
 
 @SuppressWarnings("serial")
-class ElementalObjectNode extends ObjectNode implements UnsupportedJsonValueImpl {
+class ElementalObjectNode extends ObjectNode implements UnsupportedJsonValueImpl<JsonObject> {
 
   public ElementalObjectNode(JsonObject o) {
     super(JsonNodeFactory.instance, children(o));

src/main/java/com/flowingcode/vaadin/jsonmigration/ElementalStringNode.java

@@ -2,7 +2,7 @@
  * #%L
  * Json Migration Helper
  * %%
- * Copyright (C) 2025 Flowing Code
+ * Copyright (C) 2025 - 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.
@@ -19,11 +19,12 @@
  */
 package com.flowingcode.vaadin.jsonmigration;
 
+import elemental.json.JsonString;
 import elemental.json.JsonType;
 import tools.jackson.databind.node.StringNode;
 
 @SuppressWarnings("serial")
-class ElementalStringNode extends StringNode implements UnsupportedJsonValueImpl {
+class ElementalStringNode extends StringNode implements UnsupportedJsonValueImpl<JsonString> {
 
   public ElementalStringNode(String value) {
     super(value);

src/main/java/com/flowingcode/vaadin/jsonmigration/UnsupportedJsonValueImpl.java

@@ -2,7 +2,7 @@
  * #%L
  * Json Migration Helper
  * %%
- * Copyright (C) 2025 Flowing Code
+ * Copyright (C) 2025 - 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.
@@ -22,7 +22,7 @@
 import elemental.json.JsonValue;
 import tools.jackson.databind.JsonNode;
 
-interface UnsupportedJsonValueImpl extends JsonValue {
+interface UnsupportedJsonValueImpl<T extends JsonValue> extends JsonValue {
 
   @Override
   default boolean asBoolean() {