#2439 Do not throw NPE getting accessors for null typeElement

Provide better error message if the source type has no read properties

processor/src/main/java/org/mapstruct/ap/internal/model/beanmapping/SourceReference.java

@@ -10,6 +10,7 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
 import javax.lang.model.element.AnnotationMirror;
 import javax.lang.model.element.AnnotationValue;
 import javax.lang.model.type.DeclaredType;
@@ -277,17 +278,30 @@ public class SourceReference extends AbstractReference {
                     notFoundPropertyIndex = entries.size();
                     sourceType = last( entries ).getType();
                 }
-                String mostSimilarWord = Strings.getMostSimilarWord(
+
-                    propertyNames[notFoundPropertyIndex],
+                Set<String> readProperties = sourceType.getPropertyReadAccessors().keySet();
-                    sourceType.getPropertyReadAccessors().keySet()
+
-                );
+                if ( !readProperties.isEmpty() ) {
-                List<String> elements = new ArrayList<>(
+                    String mostSimilarWord = Strings.getMostSimilarWord(
-                    Arrays.asList( propertyNames ).subList( 0, notFoundPropertyIndex )
+                        propertyNames[notFoundPropertyIndex],
-                );
+                        readProperties
-                elements.add( mostSimilarWord );
+                    );
-                reportMappingError(
+
-                    Message.PROPERTYMAPPING_INVALID_PROPERTY_NAME, sourceName, Strings.join( elements, "." )
+                    List<String> elements = new ArrayList<>(
-                );
+                        Arrays.asList( propertyNames ).subList( 0, notFoundPropertyIndex )
+                    );
+                    elements.add( mostSimilarWord );
+                    reportMappingError(
+                        Message.PROPERTYMAPPING_INVALID_PROPERTY_NAME, sourceName, Strings.join( elements, "." )
+                    );
+                }
+                else {
+                    reportMappingError(
+                        Message.PROPERTYMAPPING_INVALID_PROPERTY_NAME_SOURCE_HAS_NO_PROPERTIES,
+                        sourceName,
+                        sourceType.describe()
+                    );
+                }
             }
         }
 

processor/src/main/java/org/mapstruct/ap/internal/model/common/Type.java

@@ -14,6 +14,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -693,7 +694,7 @@ public class Type extends ModelElement implements Comparable<Type> {
 
     public List<Element> getRecordComponents() {
         if ( recordComponents == null ) {
-            recordComponents = filters.recordComponentsIn( typeElement );
+            recordComponents = nullSafeTypeElementListConversion( filters::recordComponentsIn );
         }
 
         return recordComponents;
@@ -720,7 +721,7 @@ public class Type extends ModelElement implements Comparable<Type> {
 
     private List<ExecutableElement> getAllMethods() {
         if ( allMethods == null ) {
-            allMethods = elementUtils.getAllEnclosedExecutableElements( typeElement );
+            allMethods = nullSafeTypeElementListConversion( elementUtils::getAllEnclosedExecutableElements );
         }
 
         return allMethods;
@@ -728,12 +729,20 @@ public class Type extends ModelElement implements Comparable<Type> {
 
     private List<VariableElement> getAllFields() {
         if ( allFields == null ) {
-            allFields = elementUtils.getAllEnclosedFields( typeElement );
+            allFields = nullSafeTypeElementListConversion( elementUtils::getAllEnclosedFields );
         }
 
         return allFields;
     }
 
+    private <T> List<T> nullSafeTypeElementListConversion(Function<TypeElement, List<T>> conversionFunction) {
+        if ( typeElement != null ) {
+            return conversionFunction.apply( typeElement );
+        }
+
+        return Collections.emptyList();
+    }
+
     private String getPropertyName(Accessor accessor ) {
         Element accessorElement = accessor.getElement();
         if ( accessorElement instanceof ExecutableElement ) {

processor/src/main/java/org/mapstruct/ap/internal/util/Message.java

@@ -70,6 +70,7 @@ public enum Message {
     PROPERTYMAPPING_INVALID_PARAMETER_NAME( "Method has no source parameter named \"%s\". Method source parameters are: \"%s\"." ),
     PROPERTYMAPPING_NO_PROPERTY_IN_PARAMETER( "The type of parameter \"%s\" has no property named \"%s\"." ),
     PROPERTYMAPPING_INVALID_PROPERTY_NAME( "No property named \"%s\" exists in source parameter(s). Did you mean \"%s\"?" ),
+    PROPERTYMAPPING_INVALID_PROPERTY_NAME_SOURCE_HAS_NO_PROPERTIES( "No property named \"%s\" exists in source parameter(s). Type \"%s\" has no properties." ),
     PROPERTYMAPPING_NO_PRESENCE_CHECKER_FOR_SOURCE_TYPE( "Using custom source value presence checking strategy, but no presence checker found for %s in source type." ),
     PROPERTYMAPPING_NO_READ_ACCESSOR_FOR_TARGET_TYPE( "No read accessor found for property \"%s\" in target type." ),
     PROPERTYMAPPING_NO_WRITE_ACCESSOR_FOR_TARGET_TYPE( "No write accessor found for property \"%s\" in target type." ),

processor/src/test/java/org/mapstruct/ap/test/bugs/_2439/ErroneousIssue2439Mapper.java

@@ -0,0 +1,48 @@
+/*
+ * 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._2439;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper
+public interface ErroneousIssue2439Mapper {
+
+    @Mapping(target = "modeName", source = "mode.desc")
+    LiveDto map(LiveEntity entity);
+
+    class LiveEntity {
+        private final LiveMode[] mode;
+
+        public LiveEntity(LiveMode... mode) {
+            this.mode = mode;
+        }
+
+        public LiveMode[] getMode() {
+            return mode;
+        }
+    }
+
+    class LiveDto {
+        private String modeName;
+
+        public String getModeName() {
+            return modeName;
+        }
+
+        public void setModeName(String modeName) {
+            this.modeName = modeName;
+        }
+    }
+
+    enum LiveMode {
+        TEST,
+        PROD,
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/bugs/_2439/Issuer2439Test.java

@@ -0,0 +1,38 @@
+/*
+ * 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._2439;
+
+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
+ */
+@IssueKey("2439")
+@WithClasses({
+    ErroneousIssue2439Mapper.class
+})
+class Issuer2439Test {
+
+    @ProcessorTest
+    @ExpectedCompilationOutcome(
+        value = CompilationResult.FAILED,
+        diagnostics = {
+            @Diagnostic(type = ErroneousIssue2439Mapper.class,
+                kind = javax.tools.Diagnostic.Kind.ERROR,
+                line = 17,
+                message = "No property named \"mode.desc\" exists in source parameter(s)." +
+                    " Type \"ErroneousIssue2439Mapper.LiveMode[]\" has no properties.")
+        }
+    )
+    void shouldProvideGoodErrorMessage() {
+
+    }
+}