Only customize annotationProcessor scope with Gradle 4+

Closes gh-848

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/GradleAnnotationProcessorScopeBuildCustomizer.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.build.gradle;
+
+import io.spring.initializr.generator.buildsystem.DependencyScope;
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
+import io.spring.initializr.generator.spring.build.BuildCustomizer;
+
+import org.springframework.core.Ordered;
+
+/**
+ * Gradle {@link BuildCustomizer} that adds a workaround so that annotation processors are
+ * properly detected when using the `annotationProcessor` scope.
+ *
+ * @author Stephane Nicoll
+ */
+public class GradleAnnotationProcessorScopeBuildCustomizer
+		implements BuildCustomizer<GradleBuild> {
+
+	@Override
+	public void customize(GradleBuild build) {
+		boolean annotationProcessorUsed = build.dependencies().items()
+				.anyMatch((dependency) -> dependency
+						.getScope() == DependencyScope.ANNOTATION_PROCESSOR);
+		if (annotationProcessorUsed) {
+			build.customizeConfiguration("compileOnly",
+					(configuration) -> configuration.extendsFrom("annotationProcessor"));
+		}
+	}
+
+	@Override
+	public int getOrder() {
+		return Ordered.LOWEST_PRECEDENCE;
+	}
+
+}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/GradleProjectGenerationConfiguration.java

@@ -200,6 +200,11 @@ public class GradleProjectGenerationConfiguration {
 					projectDescription.getPlatformVersion().toString());
 		}
 
+		@Bean
+		public GradleAnnotationProcessorScopeBuildCustomizer gradleAnnotationProcessorScopeBuildCustomizer() {
+			return new GradleAnnotationProcessorScopeBuildCustomizer();
+		}
+
 	}
 
 }