Making processor a bit more robust against source files missing in compilation

processor/src/main/java/org/mapstruct/ap/AnnotationProcessingException.java

@@ -18,12 +18,15 @@
  */
 package org.mapstruct.ap;
 
+import javax.annotation.processing.Messager;
 import javax.lang.model.element.AnnotationMirror;
 import javax.lang.model.element.AnnotationValue;
 import javax.lang.model.element.Element;
 
 /**
- * Indicates an error during annotation processing.
+ * Indicates an error during annotation processing. Should only be thrown in non-recoverable situations such as errors
+ * due to incomplete compilations etc. Expected errors to be propagated to the user of the annotation processor should
+ * be raised using the {@link Messager} API instead.
  *
  * @author Gunnar Morling
  */
@@ -34,6 +37,10 @@ public class AnnotationProcessingException extends RuntimeException {
     private final AnnotationMirror annotationMirror;
     private final AnnotationValue annotationValue;
 
+    public AnnotationProcessingException(String message) {
+        this( message, null, null, null );
+    }
+
     public AnnotationProcessingException(String message, Element element) {
         this( message, element, null, null );
     }

processor/src/main/java/org/mapstruct/ap/processor/MethodRetrievalProcessor.java

@@ -18,10 +18,13 @@
  */
 package org.mapstruct.ap.processor;
 
+import static javax.lang.model.util.ElementFilter.methodsIn;
+
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+
 import javax.annotation.processing.Messager;
 import javax.lang.model.element.ExecutableElement;
 import javax.lang.model.element.Modifier;
@@ -31,6 +34,7 @@ import javax.lang.model.type.TypeKind;
 import javax.lang.model.type.TypeMirror;
 import javax.tools.Diagnostic.Kind;
 
+import org.mapstruct.ap.AnnotationProcessingException;
 import org.mapstruct.ap.IterableMappingPrism;
 import org.mapstruct.ap.MapMappingPrism;
 import org.mapstruct.ap.MapperPrism;
@@ -45,8 +49,6 @@ import org.mapstruct.ap.model.source.Method;
 import org.mapstruct.ap.util.Executables;
 import org.mapstruct.ap.util.TypeFactory;
 
-import static javax.lang.model.util.ElementFilter.methodsIn;
-
 /**
  * A {@link ModelElementProcessor} which retrieves a list of {@link Method}s
  * representing all the mapping methods of the given bean mapper type as well as
@@ -88,8 +90,6 @@ public class MethodRetrievalProcessor implements ModelElementProcessor<Void, Lis
     private List<Method> retrieveMethods(TypeElement element, boolean mapperRequiresImplementation) {
         List<Method> methods = new ArrayList<Method>();
 
-        MapperPrism mapperPrism = mapperRequiresImplementation ? MapperPrism.getInstanceOn( element ) : null;
-
         for ( ExecutableElement executable : methodsIn( element.getEnclosedElements() ) ) {
             Method method = getMethod( element, executable, mapperRequiresImplementation );
             if ( method != null ) {
@@ -99,6 +99,13 @@ public class MethodRetrievalProcessor implements ModelElementProcessor<Void, Lis
 
         //Add all methods of used mappers in order to reference them in the aggregated model
         if ( mapperRequiresImplementation ) {
+            MapperPrism mapperPrism = MapperPrism.getInstanceOn( element );
+            if ( !mapperPrism.isValid ) {
+                throw new AnnotationProcessingException(
+                    "Couldn't retrieve @Mapper annotation", element, mapperPrism.mirror
+                );
+            }
+
             for ( TypeMirror usedMapper : mapperPrism.uses() ) {
                 methods.addAll(
                     retrieveMethods(

processor/src/main/java/org/mapstruct/ap/util/TypeFactory.java

@@ -42,6 +42,7 @@ import javax.lang.model.type.TypeMirror;
 import javax.lang.model.util.Elements;
 import javax.lang.model.util.Types;
 
+import org.mapstruct.ap.AnnotationProcessingException;
 import org.mapstruct.ap.model.Type;
 
 /**
@@ -100,6 +101,10 @@ public class TypeFactory {
     }
 
     public Type getType(TypeMirror mirror) {
+        if ( mirror.getKind() == TypeKind.ERROR ) {
+            throw new AnnotationProcessingException( "Encountered erroneous type " + mirror );
+        }
+
         Type implementationType = getImplementationType( mirror );
 
         boolean isIterableType = typeUtils.isSubtype(

processor/src/test/java/org/mapstruct/ap/testutil/MapperTestBase.java

@@ -305,7 +305,10 @@ public abstract class MapperTestBase {
 
         @Override
         public int compare(DiagnosticDescriptor o1, DiagnosticDescriptor o2) {
-            int result = o1.getSourceFileName().compareTo( o2.getSourceFileName() );
+            String sourceFileName1 = o1.getSourceFileName() != null ? o1.getSourceFileName() : "";
+            String sourceFileName2 = o2.getSourceFileName() != null ? o2.getSourceFileName() : "";
+
+            int result = sourceFileName1.compareTo( sourceFileName2 );
 
             if ( result != 0 ) {
                 return result;