Allow contributors to be filtered

This commit exposes an additional protected method in ProjectGenerator
that sub-classes can override to alter the list of
`@ProjectGenerationConfiguration`-annotated types that are used to load
candidate contributors.

Closes gh-870

initializr-generator/src/main/java/io/spring/initializr/generator/project/ProjectGenerator.java

@@ -21,12 +21,9 @@ import java.util.List;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 
-import org.springframework.context.annotation.Configuration;
-import org.springframework.context.annotation.Import;
-import org.springframework.context.annotation.ImportSelector;
+import org.springframework.beans.factory.support.GenericBeanDefinition;
 import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.core.io.support.SpringFactoriesLoader;
-import org.springframework.core.type.AnnotationMetadata;
 
 /**
  * Main entry point for project generation that processes a {@link ProjectDescription} by
@@ -104,8 +101,8 @@ public class ProjectGenerator {
 	public <T> T generate(ProjectDescription description, ProjectAssetGenerator<T> projectAssetGenerator)
 			throws ProjectGenerationException {
 		try (ProjectGenerationContext context = this.contextFactory.get()) {
-			context.registerBean(ProjectDescription.class, resolve(description, context));
-			context.register(CoreConfiguration.class);
+			registerProjectDescription(context, description);
+			registerProjectContributors(context, description);
 			this.contextConsumer.accept(context);
 			context.refresh();
 			try {
@@ -117,6 +114,30 @@ public class ProjectGenerator {
 		}
 	}
 
+	/**
+	 * Return the {@link ProjectGenerationConfiguration} class names that should be
+	 * considered. By default this method will load candidates using
+	 * {@link SpringFactoriesLoader} with {@link ProjectGenerationConfiguration}.
+	 * @param description the description of the project to generate
+	 * @return a list of candidate configurations
+	 */
+	protected List<String> getCandidateProjectGenerationConfigurations(ProjectDescription description) {
+		return SpringFactoriesLoader.loadFactoryNames(ProjectGenerationConfiguration.class,
+				getClass().getClassLoader());
+	}
+
+	private void registerProjectDescription(ProjectGenerationContext context, ProjectDescription description) {
+		context.registerBean(ProjectDescription.class, resolve(description, context));
+	}
+
+	private void registerProjectContributors(ProjectGenerationContext context, ProjectDescription description) {
+		getCandidateProjectGenerationConfigurations(description).forEach((configurationClassName) -> {
+			GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
+			beanDefinition.setBeanClassName(configurationClassName);
+			context.registerBeanDefinition(configurationClassName, beanDefinition);
+		});
+	}
+
 	private Supplier<ProjectDescription> resolve(ProjectDescription description, ProjectGenerationContext context) {
 		return () -> {
 			if (description instanceof MutableProjectDescription) {
@@ -134,30 +155,4 @@ public class ProjectGenerator {
 		};
 	}
 
-	/**
-	 * {@link Configuration} class that registers all available
-	 * {@link ProjectGenerationConfiguration} classes.
-	 */
-	@Configuration
-	@Import(ProjectGenerationImportSelector.class)
-	static class CoreConfiguration {
-
-	}
-
-	/**
-	 * {@link ImportSelector} for loading classes configured in {@code spring.factories}
-	 * using the
-	 * {@code io.spring.initializr.generator.project.ProjectGenerationConfiguration} key.
-	 */
-	static class ProjectGenerationImportSelector implements ImportSelector {
-
-		@Override
-		public String[] selectImports(AnnotationMetadata importingClassMetadata) {
-			List<String> factories = SpringFactoriesLoader.loadFactoryNames(ProjectGenerationConfiguration.class,
-					getClass().getClassLoader());
-			return factories.toArray(new String[0]);
-		}
-
-	}
-
 }

initializr-generator/src/test/java/io/spring/initializr/generator/project/ProjectGeneratorTests.java

@@ -17,10 +17,16 @@
 package io.spring.initializr.generator.project;
 
 import java.io.IOException;
+import java.nio.file.Path;
+import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
 
+import io.spring.initializr.generator.buildsystem.maven.MavenBuildSystem;
+import io.spring.initializr.generator.project.contributor.TestProjectGenerationConfiguration;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
 import org.mockito.InOrder;
 
 import org.springframework.beans.factory.support.BeanDefinitionOverrideException;
@@ -166,6 +172,27 @@ public class ProjectGeneratorTests {
 		assertThat(candidates).containsOnly(entry("testBean", "duplicate"));
 	}
 
+	@Test
+	void generateCanBeExtendedToFilterProjectContributors(@TempDir Path projectDir) {
+		ProjectDescription description = mock(ProjectDescription.class);
+		given(description.getArtifactId()).willReturn("test-custom-contributor");
+		given(description.getBuildSystem()).willReturn(new MavenBuildSystem());
+		ProjectGenerator generator = new ProjectGenerator(mockContextInitializr()) {
+			@Override
+			protected List<String> getCandidateProjectGenerationConfigurations(ProjectDescription description) {
+				assertThat(description).isSameAs(description);
+				return Collections.singletonList(TestProjectGenerationConfiguration.class.getName());
+			}
+		};
+		DefaultProjectAssetGenerator assetGenerator = new DefaultProjectAssetGenerator((desc) -> projectDir);
+		Path outputDir = generator.generate(description, assetGenerator);
+		Path expectedFile = outputDir.resolve("artifact-id.txt");
+		assertThat(expectedFile).isRegularFile();
+		assertThat(expectedFile).hasContent("test-custom-contributor");
+		verify(description).getArtifactId();
+		verify(description).getBuildSystem();
+	}
+
 	@SuppressWarnings("unchecked")
 	private Consumer<ProjectGenerationContext> mockContextInitializr() {
 		return mock(Consumer.class);

initializr-generator/src/test/java/io/spring/initializr/generator/project/contributor/TestProjectGenerationConfiguration.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2012-2020 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
+ *
+ *      https://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.project.contributor;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import io.spring.initializr.generator.buildsystem.maven.MavenBuildSystem;
+import io.spring.initializr.generator.condition.ConditionalOnBuildSystem;
+import io.spring.initializr.generator.project.ProjectDescription;
+import io.spring.initializr.generator.project.ProjectGenerationConfiguration;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.util.FileCopyUtils;
+
+/**
+ * Test contributors.
+ *
+ * @author Stephane Nicoll
+ */
+@ProjectGenerationConfiguration
+public class TestProjectGenerationConfiguration {
+
+	@Bean
+	@ConditionalOnBuildSystem(MavenBuildSystem.ID)
+	public ProjectContributor testArtifactIdContributor(ProjectDescription description) {
+		return (projectRoot) -> {
+			Path testFile = projectRoot.resolve("artifact-id.txt");
+			Files.createFile(testFile);
+			FileCopyUtils.copy(description.getArtifactId(), Files.newBufferedWriter(testFile));
+		};
+	}
+
+}