#2347 Do not generate mapper implementation for private mappers

Provide a compiler error message instead of generating code that will not compile

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

@@ -15,6 +15,7 @@ import java.util.Set;
 import java.util.SortedSet;
 import java.util.TreeSet;
 import javax.lang.model.element.Element;
+import javax.lang.model.element.ElementKind;
 import javax.lang.model.element.ExecutableElement;
 import javax.lang.model.element.Modifier;
 import javax.lang.model.element.TypeElement;
@@ -210,6 +211,17 @@ public class MapperCreationProcessor implements ModelElementProcessor<List<Sourc
                 mappingContext.getForgedMethodsUnderCreation().keySet() );
         }
 
+        if ( element.getModifiers().contains( Modifier.PRIVATE ) ) {
+            // If the mapper element is private then we should report an error
+            // we can't generate an implementation for a private mapper
+            mappingContext.getMessager()
+                .printMessage( element,
+                    Message.GENERAL_CANNOT_IMPLEMENT_PRIVATE_MAPPER,
+                    element.getSimpleName().toString(),
+                    element.getKind() == ElementKind.INTERFACE ? "interface" : "class"
+                );
+        }
+
         return mapper;
     }
 

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

@@ -115,6 +115,7 @@ public enum Message {
     DECORATOR_NO_SUBTYPE( "Specified decorator type is no subtype of the annotated mapper type." ),
     DECORATOR_CONSTRUCTOR( "Specified decorator type has no default constructor nor a constructor with a single parameter accepting the decorated mapper type." ),
 
+    GENERAL_CANNOT_IMPLEMENT_PRIVATE_MAPPER("Cannot create an implementation for mapper %s, because it is a private %s."),
     GENERAL_NO_IMPLEMENTATION( "No implementation type is registered for return type %s." ),
     GENERAL_ABSTRACT_RETURN_TYPE( "The return type %s is an abstract class or interface. Provide a non abstract / non interface result type or a factory method." ),
     GENERAL_AMBIGUOUS_MAPPING_METHOD( "Ambiguous mapping methods found for mapping %s to %s: %s. See " + FAQ_AMBIGUOUS_URL + " for more info." ),

processor/src/test/java/org/mapstruct/ap/test/bugs/_2347/ErroneousClassWithPrivateMapper.java

@@ -0,0 +1,51 @@
+/*
+ * 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._2347;
+
+import org.mapstruct.Mapper;
+
+/**
+ * @author Filip Hrisafov
+ */
+public class ErroneousClassWithPrivateMapper {
+
+    public static class Target {
+        private final String id;
+
+        public Target(String id) {
+            this.id = id;
+        }
+
+        public String getId() {
+            return id;
+        }
+    }
+
+    public static class Source {
+
+        private final String id;
+
+        public Source(String id) {
+            this.id = id;
+        }
+
+        public String getId() {
+            return id;
+        }
+    }
+
+    @Mapper
+    private interface PrivateInterfaceMapper {
+
+        Target map(Source source);
+    }
+
+    @Mapper
+    private abstract class PrivateClassMapper {
+
+        public abstract Target map(Source source);
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/bugs/_2347/Issue2347Test.java

@@ -0,0 +1,49 @@
+/*
+ * 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._2347;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mapstruct.ap.testutil.IssueKey;
+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;
+import org.mapstruct.ap.testutil.runner.AnnotationProcessorTestRunner;
+
+/**
+ * @author Filip Hrisafov
+ */
+@IssueKey("2347")
+@RunWith(AnnotationProcessorTestRunner.class)
+@WithClasses({
+    ErroneousClassWithPrivateMapper.class
+})
+public class Issue2347Test {
+
+    @ExpectedCompilationOutcome(value = CompilationResult.FAILED,
+        diagnostics = {
+            @Diagnostic(
+                type = ErroneousClassWithPrivateMapper.class,
+                kind = javax.tools.Diagnostic.Kind.ERROR,
+                line = 41,
+                message = "Cannot create an implementation for mapper PrivateInterfaceMapper," +
+                    " because it is a private interface."
+            ),
+            @Diagnostic(
+                type = ErroneousClassWithPrivateMapper.class,
+                kind = javax.tools.Diagnostic.Kind.ERROR,
+                line = 47,
+                message = "Cannot create an implementation for mapper PrivateClassMapper," +
+                    " because it is a private class."
+            )
+        }
+    )
+    @Test
+    public void shouldGenerateCompileErrorWhenMapperIsPrivate() {
+
+    }
+}