#2185 Fix StackOverflow error when recursive use of mapper in Mapper#uses

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

@@ -176,12 +176,23 @@ public class MethodRetrievalProcessor implements ModelElementProcessor<Void, Lis
         //Add all methods of used mappers in order to reference them in the aggregated model
         if ( usedMapper.equals( mapperToImplement ) ) {
             for ( DeclaredType mapper : mapperOptions.uses() ) {
+                TypeElement usesMapperElement = asTypeElement( mapper );
+                if ( !mapperToImplement.equals( usesMapperElement ) ) {
                     methods.addAll( retrieveMethods(
-                    asTypeElement( mapper ),
+                        usesMapperElement,
                         mapperToImplement,
                         mapperOptions,
                         prototypeMethods ) );
                 }
+                else {
+                    messager.printMessage(
+                        mapperToImplement,
+                        mapperOptions.getAnnotationMirror(),
+                        Message.RETRIEVAL_MAPPER_USES_CYCLE,
+                        mapperToImplement
+                    );
+                }
+            }
         }
 
         return methods;

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

@@ -149,6 +149,7 @@ public enum Message {
     RETRIEVAL_WILDCARD_SUPER_BOUND_SOURCE( "Can't generate mapping method for a wildcard super bound source." ),
     RETRIEVAL_WILDCARD_EXTENDS_BOUND_RESULT( "Can't generate mapping method for a wildcard extends bound result." ),
     RETRIEVAL_CONTEXT_PARAMS_WITH_SAME_TYPE( "The types of @Context parameters must be unique." ),
+    RETRIEVAL_MAPPER_USES_CYCLE( "The mapper %s is referenced itself in Mapper#uses.", Diagnostic.Kind.WARNING ),
 
     INHERITINVERSECONFIGURATION_DUPLICATES( "Several matching inverse methods exist: %s(). Specify a name explicitly." ),
     INHERITINVERSECONFIGURATION_INVALID_NAME( "None of the candidates %s() matches given name: \"%s\"." ),

processor/src/test/java/org/mapstruct/ap/test/bugs/_2185/Issue2185Test.java

@@ -0,0 +1,45 @@
+/*
+ * 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._2185;
+
+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;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Filip Hrisafov
+ */
+@IssueKey("2185")
+@RunWith(AnnotationProcessorTestRunner.class)
+@WithClasses({
+    TodoMapper.class
+})
+public class Issue2185Test {
+
+    @Test
+    @ExpectedCompilationOutcome(value = CompilationResult.SUCCEEDED,
+        diagnostics = {
+            @Diagnostic(type = TodoMapper.class,
+                kind = javax.tools.Diagnostic.Kind.WARNING,
+                line = 14,
+                message = "The mapper org.mapstruct.ap.test.bugs._2185.TodoMapper is referenced itself in Mapper#uses.")
+        }
+    )
+    public void shouldCompile() {
+
+        TodoMapper.TodoResponse response = TodoMapper.INSTANCE.toResponse( new TodoMapper.TodoEntity( "test" ) );
+
+        assertThat( response ).isNotNull();
+        assertThat( response.getNote() ).isEqualTo( "test" );
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/bugs/_2185/TodoMapper.java

@@ -0,0 +1,46 @@
+/*
+ * 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._2185;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper(uses = TodoMapper.class)
+public interface TodoMapper {
+
+    TodoMapper INSTANCE = Mappers.getMapper( TodoMapper.class );
+
+    TodoResponse toResponse(TodoEntity entity);
+
+    class TodoResponse {
+
+        private final String note;
+
+        public TodoResponse(String note) {
+            this.note = note;
+        }
+
+        public String getNote() {
+            return note;
+        }
+    }
+
+    class TodoEntity {
+
+        private final String note;
+
+        public TodoEntity(String note) {
+            this.note = note;
+        }
+
+        public String getNote() {
+            return note;
+        }
+    }
+}