support oneof

mapstruct · DanielLiu1123 · Nov 5, 2025 · Nov 10, 2025 · Nov 10, 2025 · Nov 10, 2025
commit a6ad574d5e07f997ec0d1a24f662307eb379d702
diff --git a/...rc/test/resources/protobufTest/src/main/java/org/mapstruct/itest/protobuf/Everything.java b/...rc/test/resources/protobufTest/src/main/java/org/mapstruct/itest/protobuf/Everything.java
@@ -78,6 +78,12 @@ public class Everything {
     private DayOfWeek dayOfWeek;
     private Month month;
 
+    // oneof
+    private int oneofInt32;
+    private String oneofString;
+    private Integer oneofEnum;
+    private Message oneofMessage;
+
     public Integer getInt32() {
         return this.int32;
     }
@@ -390,6 +396,38 @@ public void setMonth(Month month) {
         this.month = month;
     }
 
+    public int getOneofInt32() {
+        return oneofInt32;
+    }
+
+    public void setOneofInt32(int oneofInt32) {
+        this.oneofInt32 = oneofInt32;
+    }
+
+    public String getOneofString() {
+        return oneofString;
+    }
+
+    public void setOneofString(String oneofString) {
+        this.oneofString = oneofString;
+    }
+
+    public Integer getOneofEnum() {
+        return oneofEnum;
+    }
+
+    public void setOneofEnum(Integer oneofEnum) {
+        this.oneofEnum = oneofEnum;
+    }
+
+    public Message getOneofMessage() {
+        return oneofMessage;
+    }
+
+    public void setOneofMessage(Message oneofMessage) {
+        this.oneofMessage = oneofMessage;
+    }
+
     public static class Message {
         private long id;
         private String name;

diff --git a/...t/resources/protobufTest/src/main/java/org/mapstruct/itest/protobuf/EverythingMapper.java b/...t/resources/protobufTest/src/main/java/org/mapstruct/itest/protobuf/EverythingMapper.java
@@ -5,19 +5,19 @@
  */
 package org.mapstruct.itest.protobuf;
 
-import static org.mapstruct.NullValueCheckStrategy.ALWAYS;
-import static org.mapstruct.ReportingPolicy.ERROR;
-
-import org.mapstruct.itest.protobuf.EverythingModel;
-import org.mapstruct.itest.protobuf.Everything;
 import org.mapstruct.Mapper;
 import org.mapstruct.Mapping;
 import org.mapstruct.factory.Mappers;
+import org.mapstruct.itest.protobuf.Everything;
+import org.mapstruct.itest.protobuf.EverythingModel;
+
+import static org.mapstruct.NullValueCheckStrategy.ALWAYS;
+import static org.mapstruct.ReportingPolicy.ERROR;
 
-@Mapper(nullValueCheckStrategy = ALWAYS, unmappedTargetPolicy = ERROR)
+@Mapper(nullValueCheckStrategy = ALWAYS, unmappedTargetPolicy = ERROR, unmappedSourcePolicy = ERROR)
 public interface EverythingMapper {
 
-    EverythingMapper INSTANCE = Mappers.getMapper(EverythingMapper.class);
+    EverythingMapper INSTANCE = Mappers.getMapper( EverythingMapper.class );
 
     @Mapping(target = "float_", source = "float")
     @Mapping(target = "double_", source = "double")

diff --git a/integrationtest/src/test/resources/protobufTest/src/main/proto/everything.proto b/integrationtest/src/test/resources/protobufTest/src/main/proto/everything.proto
@@ -69,6 +69,14 @@ message EverythingModel {
   google.type.DayOfWeek day_of_week = 73;
   google.type.Month month = 74;
 
+  // oneof field
+  oneof oneof {
+    int32 oneof_int32 = 80;
+    string oneof_string = 81;
+    Enum oneof_enum = 82;
+    Message oneof_message = 83;
+  }
+
   message Message {
     int64 id = 1;
     string name = 2;

diff --git a/processor/src/main/java/org/mapstruct/ap/spi/ProtobufAccessorNamingStrategy.java b/processor/src/main/java/org/mapstruct/ap/spi/ProtobufAccessorNamingStrategy.java
@@ -6,6 +6,7 @@
 package org.mapstruct.ap.spi;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -188,7 +189,7 @@ private Map<String, Set<MethodSignature>> getInternalMethods() {
             MESSAGE_LITE_BUILDER,
         };
 
-        Map<String, Set<MethodSignature>> methodsMap = new java.util.HashMap<>();
+        Map<String, Set<MethodSignature>> methodsMap = new HashMap<>();
         for ( String className : internalClasses ) {
             TypeElement typeElement = elementUtils.getTypeElement( className );
             if ( typeElement != null ) {
@@ -333,6 +334,14 @@ && isMapType( m.getReturnType() )
             }
         ) );
 
+        // oneof field generates extra 'getXxxCase()'
+        rules.add( new SpecialMethodRule(
+            method -> getMethodName( method ).endsWith( "Case" )
+                && isEnumType( method.getReturnType() )
+                && !isProtobufEnumType( method.getReturnType() ),
+            (method, methods) -> true
+        ) );
+
         return rules;
     }
 
@@ -485,6 +494,14 @@ private boolean isProtobufEnumType(TypeMirror t) {
         return typeUtils.isSubtype( t, protobufEnumType );
     }
 
+    private boolean isEnumType(TypeMirror t) {
+        if ( t.getKind() != TypeKind.DECLARED ) {
+            return false;
+        }
+        Element element = ( (DeclaredType) t ).asElement();
+        return element.getKind() == ElementKind.ENUM;
+    }
+
     private boolean isGetList(ExecutableElement element) {
         // repeated fields getter: getXxxList()
         return hasPrefixWithUpperCaseNext( element, "get" )