Add fixes for running the GemProcessor on Java 18+

Author: filiphr

processor/src/main/java/org/mapstruct/tools/gem/processor/GemInfo.java

@@ -5,9 +5,11 @@
  */
 package org.mapstruct.tools.gem.processor;
 
+import java.util.Arrays;
 import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
+import javax.lang.model.element.Element;
 
 public class GemInfo {
 
@@ -22,16 +24,18 @@ public class GemInfo {
     private final String builderImplName;
 
     private final List<GemValueInfo> gemValueInfos;
+    private final Element[] originatingElements;
 
     public GemInfo(String gemPackageName, String annotationName, String annotationFqn,
-        List<GemValueInfo> gemValueInfos) {
+        List<GemValueInfo> gemValueInfos, Element... originatingElements) {
         this.gemPackageName = gemPackageName;
         this.gemName = annotationName + "Gem";
         this.annotationName = annotationName;
         this.annotationFqn = annotationFqn;
         this.gemValueInfos = gemValueInfos;
         this.builderName = BUILDER_NAME + ( BUILDER_NAME.equals( annotationName ) ? "_" : "" );
         this.builderImplName = BUILDER_IMPL_NAME + ( BUILDER_IMPL_NAME.equals( annotationName ) ? "_" : "" );
+        this.originatingElements = Arrays.copyOf( originatingElements, originatingElements.length );
     }
 
     public String getGemName() {
@@ -71,6 +75,10 @@ public String getBuilderImplName() {
         return builderImplName;
     }
 
+    public Element[] getOriginatingElements() {
+        return originatingElements;
+    }
+
     private boolean isNotSamePackage(GemValueType valueType ) {
         return !valueType.getPacakage().equals( gemPackageName );
     }

processor/src/main/java/org/mapstruct/tools/gem/processor/GemProcessor.java

@@ -105,7 +105,14 @@ private void addGemInfo(AnnotationMirror gemDefinitionMirror, Element definingEl
         List<GemValueInfo> gemValueInfos = methods.stream()
             .map( e -> new GemValueInfo( e.getSimpleName().toString(), e.getReturnType() ) )
             .collect( Collectors.toList() );
-        GemInfo gemInfo = new GemInfo( gemPackage, gemName, gemFqn, gemValueInfos );
+        GemInfo gemInfo = new GemInfo(
+            gemPackage,
+            gemName,
+            gemFqn,
+            gemValueInfos,
+            definingElement,
+            gemDeclaredType.asElement()
+        );
         gemInfos.add( gemInfo );
     }
 
@@ -183,11 +190,12 @@ else if (String.class.getName().equals( fqn ) ) {
     }
 
     private void write( ) {
-        TypeElement gemElement = processingEnv.getElementUtils()
-            .getTypeElement( "org.annotationhelper.GemDefinitions" );
         for ( GemInfo gemInfo : gemInfos ) {
             try (Writer writer = processingEnv.getFiler()
-                .createSourceFile( gemInfo.getGemPackageName() + "." + gemInfo.getGemName(), gemElement )
+                .createSourceFile(
+                    gemInfo.getGemPackageName() + "." + gemInfo.getGemName(),
+                    gemInfo.getOriginatingElements()
+                )
                 .openWriter()) {
                 Configuration cfg = new Configuration( new Version( "2.3.21" ) );
                 cfg.setClassForTemplateLoading( GemProcessor.class, "/" );