#2867 Fix NPE when reporting message on parent mappers

processor/src/main/java/org/mapstruct/ap/internal/processor/MapperAnnotatedFormattingMessenger.java

@@ -5,6 +5,7 @@
  */
 package org.mapstruct.ap.internal.processor;
 
+import java.util.Objects;
 import java.util.stream.Collectors;
 import javax.lang.model.element.AnnotationMirror;
 import javax.lang.model.element.AnnotationValue;
@@ -12,6 +13,7 @@ import javax.lang.model.element.Element;
 import javax.lang.model.element.ExecutableElement;
 import javax.lang.model.element.TypeElement;
 import javax.lang.model.element.VariableElement;
+import javax.lang.model.type.TypeMirror;
 import javax.tools.Diagnostic.Kind;
 
 import org.mapstruct.ap.internal.util.FormattingMessager;
@@ -97,7 +99,7 @@ public class MapperAnnotatedFormattingMessenger implements FormattingMessager {
         if ( e instanceof ExecutableElement ) {
             ExecutableElement ee = (ExecutableElement) e;
             StringBuilder method = new StringBuilder();
-            method.append( typeUtils.asElement( ee.getReturnType() ).getSimpleName() );
+            method.append( typeMirrorToString( ee.getReturnType() ) );
             method.append( " " );
             method.append( ee.getSimpleName() );
             method.append( "(" );
@@ -112,7 +114,12 @@ public class MapperAnnotatedFormattingMessenger implements FormattingMessager {
     }
 
     private String parameterToString(VariableElement element) {
-        return typeUtils.asElement( element.asType() ).getSimpleName() + " " + element.getSimpleName();
+        return typeMirrorToString( element.asType() ) + " " + element.getSimpleName();
+    }
+
+    private String typeMirrorToString(TypeMirror type) {
+        Element element = typeUtils.asElement( type );
+        return element != null ? element.getSimpleName().toString() : Objects.toString( type );
     }
 
     private Message determineDelegationMessage(Element e, Message msg) {

processor/src/test/java/org/mapstruct/ap/test/bugs/_2867/Issue2867BaseMapper.java

@@ -0,0 +1,17 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.bugs._2867;
+
+import org.mapstruct.MappingTarget;
+
+/**
+ * @author Filip Hrisafov
+ */
+public interface Issue2867BaseMapper<T, S> {
+
+    void update(@MappingTarget T target, S source);
+
+}

processor/src/test/java/org/mapstruct/ap/test/bugs/_2867/Issue2867Mapper.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.bugs._2867;
+
+import org.mapstruct.Mapper;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper
+public interface Issue2867Mapper extends Issue2867BaseMapper<Issue2867Mapper.Target, Issue2867Mapper.Source> {
+
+    class Target {
+
+        private String name;
+
+        public String getName() {
+            return name;
+        }
+
+        public void setName(String name) {
+            this.name = name;
+        }
+    }
+
+    class Source {
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/bugs/_2867/Issue2867Test.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.bugs._2867;
+
+import org.mapstruct.ap.testutil.IssueKey;
+import org.mapstruct.ap.testutil.ProcessorTest;
+import org.mapstruct.ap.testutil.WithClasses;
+import org.mapstruct.ap.testutil.compilation.annotation.CompilationResult;
+import org.mapstruct.ap.testutil.compilation.annotation.Diagnostic;
+import org.mapstruct.ap.testutil.compilation.annotation.ExpectedCompilationOutcome;
+
+/**
+ * @author Filip Hrisafov
+ */
+@WithClasses({
+    Issue2867BaseMapper.class,
+    Issue2867Mapper.class,
+})
+@IssueKey("2867")
+class Issue2867Test {
+
+    @ExpectedCompilationOutcome(
+        value = CompilationResult.SUCCEEDED,
+        diagnostics = @Diagnostic(
+            type = Issue2867Mapper.class,
+            kind = javax.tools.Diagnostic.Kind.WARNING,
+            line = 14,
+            message = "Unmapped target property: \"name\"." +
+                " Occured at 'void update(T target, S source)' in 'Issue2867BaseMapper'."
+        )
+    )
+    @ProcessorTest
+    void shouldCompile() {
+
+    }
+}