#2478 Make sure that forged methods do not generate duplicate method parameters

processor/src/main/java/org/mapstruct/ap/internal/model/ForgedMethod.java

@@ -10,6 +10,7 @@ import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Objects;
+import java.util.stream.Collectors;
 import javax.lang.model.element.ExecutableElement;
 
 import org.mapstruct.ap.internal.model.beanmapping.MappingReferences;
@@ -125,7 +126,16 @@ public class ForgedMethod implements Method {
                          boolean forgedNameBased) {
 
         // establish name
-        String sourceParamSafeName = Strings.getSafeVariableName( sourceType.getName() );
+        String sourceParamSafeName;
+        if ( additionalParameters.isEmpty() ) {
+            sourceParamSafeName = Strings.getSafeVariableName( sourceType.getName() );
+        }
+        else {
+            sourceParamSafeName = Strings.getSafeVariableName(
+                sourceType.getName(),
+                additionalParameters.stream().map( Parameter::getName ).collect( Collectors.toList() )
+            );
+        }
 
         // establish parameters
         this.parameters = new ArrayList<>( 1 + additionalParameters.size() );

processor/src/test/java/org/mapstruct/ap/test/bugs/_2478/Issue2478Mapper.java

@@ -0,0 +1,86 @@
+/*
+ * 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._2478;
+
+import org.mapstruct.Context;
+import org.mapstruct.Mapper;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper
+public interface Issue2478Mapper {
+
+    Issue2478Mapper INSTANCE = Mappers.getMapper( Issue2478Mapper.class );
+
+    ProductEntity productFromDto(Product dto, @Context Shop shop);
+
+    class Product {
+        protected final String name;
+        protected final Shop shop;
+
+        public Product(String name, Shop shop) {
+            this.name = name;
+            this.shop = shop;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        public Shop getShop() {
+            return shop;
+        }
+    }
+
+    class Shop {
+        protected final String name;
+
+        public Shop(String name) {
+            this.name = name;
+        }
+
+        public String getName() {
+            return name;
+        }
+    }
+
+    class ProductEntity {
+
+        protected String name;
+        protected ShopEntity shop;
+
+        public String getName() {
+            return name;
+        }
+
+        public void setName(String name) {
+            this.name = name;
+        }
+
+        public ShopEntity getShop() {
+            return shop;
+        }
+
+        public void setShop(ShopEntity shop) {
+            this.shop = shop;
+        }
+    }
+
+    class ShopEntity {
+        protected String name;
+
+        public String getName() {
+            return name;
+        }
+
+        public void setName(String name) {
+            this.name = name;
+        }
+    }
+
+}

processor/src/test/java/org/mapstruct/ap/test/bugs/_2478/Issue2478Test.java

@@ -0,0 +1,33 @@
+/*
+ * 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._2478;
+
+import org.mapstruct.ap.testutil.IssueKey;
+import org.mapstruct.ap.testutil.ProcessorTest;
+import org.mapstruct.ap.testutil.WithClasses;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Filip Hrisafov
+ */
+@IssueKey("2478")
+@WithClasses({
+    Issue2478Mapper.class
+})
+class Issue2478Test {
+
+    @ProcessorTest
+    void shouldGenerateCodeThatCompiles() {
+        Issue2478Mapper.Product dto = new Issue2478Mapper.Product( "Test", new Issue2478Mapper.Shop( "Shopify" ) );
+        Issue2478Mapper.ProductEntity entity = Issue2478Mapper.INSTANCE.productFromDto( dto, dto.getShop() );
+
+        assertThat( entity ).isNotNull();
+        assertThat( entity.getName() ).isEqualTo( "Test" );
+        assertThat( entity.getShop() ).isNotNull();
+        assertThat( entity.getShop().getName() ).isEqualTo( "Shopify" );
+    }
+}