Add generics support

src/main/java/org/mapstruct/intellij/codeinsight/references/MapstructBaseReference.java

@@ -18,6 +18,7 @@
 import com.intellij.psi.PsiReferenceExpression;
 import com.intellij.psi.PsiType;
 import com.intellij.psi.util.PsiTreeUtil;
+import com.intellij.psi.util.PsiUtil;
 import com.intellij.util.IncorrectOperationException;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -148,6 +149,24 @@ public final Object[] getVariants() {
     @Nullable
     abstract PsiType resolvedType();
 
+    /**
+     * Substitutes type parameters in {@code memberType} using the generic context from the previous reference in the
+     * property chain.
+     */
+    @Nullable
+    protected PsiType substituteMemberType(@Nullable PsiType memberType) {
+        if ( memberType == null || previous == null ) {
+            return memberType;
+        }
+
+        PsiType ownerType = previous.resolvedType();
+        if ( ownerType == null ) {
+            return memberType;
+        }
+
+        return PsiUtil.resolveGenericsClassInType( ownerType ).getSubstitutor().substitute( memberType );
+    }
+
     @Override
     public PsiElement handleElementRename(@NotNull String newElementName) throws IncorrectOperationException {
         PsiElement reference = resolve();

src/main/java/org/mapstruct/intellij/codeinsight/references/MapstructSourceReference.java

@@ -135,16 +135,16 @@ PsiType resolvedType() {
         PsiElement element = resolve();
 
         if ( element instanceof PsiMethod psiMethod ) {
-            return psiMethod.getReturnType();
+            return substituteMemberType( psiMethod.getReturnType() );
         }
         else if ( element instanceof PsiParameter psiParameter ) {
             return psiParameter.getType();
         }
         else if ( element instanceof PsiRecordComponent psiRecordComponent ) {
-            return psiRecordComponent.getType();
+            return substituteMemberType( psiRecordComponent.getType() );
         }
         else if ( element instanceof PsiField psiField ) {
-            return psiField.getType();
+            return substituteMemberType( psiField.getType() );
         }
 
         return null;

src/main/java/org/mapstruct/intellij/codeinsight/references/MapstructTargetReference.java

@@ -205,16 +205,16 @@ PsiType resolvedType() {
         PsiElement element = resolve();
 
         if ( element instanceof PsiMethod psiMethod ) {
-            return firstParameterPsiType( psiMethod );
+            return substituteMemberType( firstParameterPsiType( psiMethod ) );
         }
         else if ( element instanceof PsiParameter psiParameter ) {
             return psiParameter.getType();
         }
         else if ( element instanceof PsiRecordComponent psiRecordComponent ) {
-            return psiRecordComponent.getType();
+            return substituteMemberType( psiRecordComponent.getType() );
         }
         else if ( element instanceof PsiField psiField ) {
-            return psiField.getType();
+            return substituteMemberType( psiField.getType() );
         }
 
         return null;

src/test/java/org/mapstruct/intellij/MapstructBaseCompletionTestCase.java

@@ -5,16 +5,15 @@
  */
 package org.mapstruct.intellij;
 
-import java.io.File;
-
 import com.intellij.codeInsight.completion.LightFixtureCompletionTestCase;
 import com.intellij.openapi.util.text.StringUtil;
-import com.intellij.openapi.vfs.newvfs.impl.VfsRootAccess;
 import com.intellij.testFramework.LightProjectDescriptor;
 import com.intellij.testFramework.PsiTestUtil;
 import com.intellij.util.PathUtil;
 import org.jetbrains.annotations.NotNull;
 
+import java.io.File;
+
 /**
  * Base completion test case for MapStruct.
  *
@@ -29,7 +28,13 @@ protected void setUp() throws Exception {
         super.setUp();
         final String mapstructLibPath = PathUtil.toSystemIndependentName( new File( BUILD_LIBS_DIRECTORY )
             .getAbsolutePath() );
-        VfsRootAccess.allowRootAccess( getTestRootDisposable(), mapstructLibPath );
+
+        allowAccessToDirsIfExists(
+                BUILD_LIBS_DIRECTORY,
+                "testData",
+                "build/test-libs"
+        );
+
         PsiTestUtil.addLibrary(
             myFixture.getProjectDisposable(),
             myFixture.getModule(),

src/test/java/org/mapstruct/intellij/MapstructCompletionTestCase.java

@@ -488,6 +488,36 @@ public void testFluentGenericTargetMapper() {
             );
     }
 
+    public void testGenericCarWrapperSourceAutoCompleteAfterCar() {
+        configureByTestName();
+
+        assertThat( myItems )
+            .extracting( LookupElement::getLookupString )
+            .containsExactlyInAnyOrder(
+                "winCode"
+            );
+
+        assertThat( myItems )
+            .extracting( LookupElementPresentation::renderElement )
+            .usingRecursiveFieldByFieldElementComparator()
+            .containsExactlyInAnyOrder(
+                createVariable( "winCode", "String" )
+            );
+    }
+
+    public void testGenericCarWrapperTargetAutoCompleteAfterCar() {
+        configureByTestName();
+
+        assertThat( myItems )
+            .extracting( LookupElement::getLookupString )
+            .containsExactlyInAnyOrder( "winCode" );
+
+        assertThat( myItems )
+            .extracting( LookupElementPresentation::renderElement )
+            .usingRecursiveFieldByFieldElementComparator()
+            .containsExactlyInAnyOrder( createVariable( "winCode", "String" ) );
+    }
+
     public void testVariantsCarMapperNoSourceClass() {
         myFixture.configureByFile( "CarMapperNoSourceClass.java" );
         complete();

testData/mapping/GenericCarWrapperSourceAutoCompleteAfterCar.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at https://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.complex;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+
+@Mapper
+public interface GenericCarWrapperMapper {
+
+    @Mapping(target = "id", source = "wrapper.car.<caret>winCode")
+    CarEntity toCarDto(CarWrapper<Car> wrapper);
+}
+
+class CarEntity {
+
+    private String id;
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+}
+
+class Car {
+
+    private String winCode;
+
+    public String getWinCode() {
+        return winCode;
+    }
+
+    public void setWinCode(String winCode) {
+        this.winCode = winCode;
+    }
+}
+
+class CarWrapper<T> {
+
+    private T car;
+
+    public T getCar() {
+        return car;
+    }
+
+    public void setCar(T car) {
+        this.car = car;
+    }
+}

testData/mapping/GenericCarWrapperTargetAutoCompleteAfterCar.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at https://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.complex;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.MappingTarget;
+
+@Mapper
+public interface GenericCarWrapperTargetMapper {
+
+    @Mapping(source = "id", target = "wrapper.car.<caret>winCode")
+    void update(@MappingTarget CarWrapper<Car> wrapper, CarEntity entity);
+}
+
+class CarEntity {
+
+    private String id;
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+}
+
+class Car {
+
+    private String winCode;
+
+    public String getWinCode() {
+        return winCode;
+    }
+
+    public void setWinCode(String winCode) {
+        this.winCode = winCode;
+    }
+}
+
+class CarWrapper<T> {
+
+    private T car;
+
+    public T getCar() {
+        return car;
+    }
+
+    public void setCar(T car) {
+        this.car = car;
+    }
+}