Group auto-configuration import selectors together

This commit updates Spring Boot's DeferredImportSelector implementations
to group imports in a consistent set. This makes sure ordering is
applied consistently.

Closes gh-12366

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationImportSelector.java

@@ -16,14 +16,16 @@
 
 package org.springframework.boot.autoconfigure;
 
-import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -88,14 +90,12 @@ public class AutoConfigurationImportSelector
 		if (!isEnabled(annotationMetadata)) {
 			return NO_IMPORTS;
 		}
-		try {
 		AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
 				.loadMetadata(this.beanClassLoader);
 		AnnotationAttributes attributes = getAttributes(annotationMetadata);
 		List<String> configurations = getCandidateConfigurations(annotationMetadata,
 				attributes);
 		configurations = removeDuplicates(configurations);
-			configurations = sort(configurations, autoConfigurationMetadata);
 		Set<String> exclusions = getExclusions(annotationMetadata, attributes);
 		checkExcludedClasses(configurations, exclusions);
 		configurations.removeAll(exclusions);
@@ -103,9 +103,10 @@ public class AutoConfigurationImportSelector
 		fireAutoConfigurationImportEvents(configurations, exclusions);
 		return StringUtils.toStringArray(configurations);
 	}
-		catch (IOException ex) {
-			throw new IllegalStateException(ex);
-		}
+
+	@Override
+	public Class<? extends Group> getImportGroup() {
+		return AutoConfigurationGroup.class;
 	}
 
 	protected boolean isEnabled(AnnotationMetadata metadata) {
@@ -226,13 +227,6 @@ public class AutoConfigurationImportSelector
 		return (excludes == null ? Collections.emptyList() : Arrays.asList(excludes));
 	}
 
-	private List<String> sort(List<String> configurations,
-			AutoConfigurationMetadata autoConfigurationMetadata) throws IOException {
-		configurations = new AutoConfigurationSorter(getMetadataReaderFactory(),
-				autoConfigurationMetadata).getInPriorityOrder(configurations);
-		return configurations;
-	}
-
 	private List<String> filter(List<String> configurations,
 			AutoConfigurationMetadata autoConfigurationMetadata) {
 		long startTime = System.nanoTime();
@@ -272,17 +266,6 @@ public class AutoConfigurationImportSelector
 				this.beanClassLoader);
 	}
 
-	private MetadataReaderFactory getMetadataReaderFactory() {
-		try {
-			return getBeanFactory().getBean(
-					SharedMetadataReaderFactoryContextInitializer.BEAN_NAME,
-					MetadataReaderFactory.class);
-		}
-		catch (NoSuchBeanDefinitionException ex) {
-			return new CachingMetadataReaderFactory(this.resourceLoader);
-		}
-	}
-
 	protected final <T> List<T> removeDuplicates(List<T> list) {
 		return new ArrayList<>(new LinkedHashSet<>(list));
 	}
@@ -370,4 +353,71 @@ public class AutoConfigurationImportSelector
 		return Ordered.LOWEST_PRECEDENCE - 1;
 	}
 
+
+	private static class AutoConfigurationGroup implements DeferredImportSelector.Group,
+			BeanClassLoaderAware, BeanFactoryAware, ResourceLoaderAware {
+
+		private ClassLoader beanClassLoader;
+
+		private BeanFactory beanFactory;
+
+		private ResourceLoader resourceLoader;
+
+		private final Map<String, AnnotationMetadata> entries = new LinkedHashMap<>();
+
+		@Override
+		public void setBeanClassLoader(ClassLoader classLoader) {
+			this.beanClassLoader = classLoader;
+		}
+
+		@Override
+		public void setBeanFactory(BeanFactory beanFactory) {
+			this.beanFactory = beanFactory;
+		}
+
+		@Override
+		public void setResourceLoader(ResourceLoader resourceLoader) {
+			this.resourceLoader = resourceLoader;
+		}
+
+		@Override
+		public void process(AnnotationMetadata annotationMetadata,
+				DeferredImportSelector deferredImportSelector) {
+			String[] imports = deferredImportSelector.selectImports(annotationMetadata);
+			for (String importClassName : imports) {
+				this.entries.put(importClassName, annotationMetadata);
+			}
+		}
+
+		@Override
+		public Iterable<Entry> selectImports() {
+			return sortAutoConfigurations().stream().map((importClassName) ->
+					new Entry(this.entries.get(importClassName), importClassName))
+					.collect(Collectors.toList());
+		}
+
+		private List<String> sortAutoConfigurations() {
+			List<String> autoConfigurations = new ArrayList<>(this.entries.keySet());
+			if (this.entries.size() <= 1) {
+				return autoConfigurations;
+			}
+			AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
+					.loadMetadata(this.beanClassLoader);
+			return new AutoConfigurationSorter(getMetadataReaderFactory(),
+					autoConfigurationMetadata).getInPriorityOrder(autoConfigurations);
+		}
+
+		private MetadataReaderFactory getMetadataReaderFactory() {
+			try {
+				return this.beanFactory.getBean(
+						SharedMetadataReaderFactoryContextInitializer.BEAN_NAME,
+						MetadataReaderFactory.class);
+			}
+			catch (NoSuchBeanDefinitionException ex) {
+				return new CachingMetadataReaderFactory(this.resourceLoader);
+			}
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/AutoConfigurationImportSelectorIntegrationTests.java

@@ -0,0 +1,132 @@
+/*
+ * Copyright 2012-2018 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 org.springframework.boot.autoconfigure;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Test;
+
+import org.springframework.boot.test.context.assertj.AssertableApplicationContext;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.util.ClassUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for {@link AutoConfigurationImportSelector}.
+ *
+ * @author Stephane Nicoll
+ */
+public class AutoConfigurationImportSelectorIntegrationTests {
+
+	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner();
+
+	@Test
+	public void singleSelectorWithNoImports() {
+		this.contextRunner.withUserConfiguration(NoConfig.class)
+				.run((context) ->
+						assertThat(getImportedConfigBeans(context)).isEmpty());
+	}
+
+	@Test
+	public void singleSelector() {
+		this.contextRunner.withUserConfiguration(SingleConfig.class)
+				.run((context) -> {
+					assertThat(getImportedConfigBeans(context)).containsExactly(
+							"ConfigC");
+				});
+	}
+
+	@Test
+	public void multipleSelectorShouldMergeAndSortCorrectly() {
+		this.contextRunner.withUserConfiguration(Config.class, AnotherConfig.class)
+				.run((context) -> {
+					assertThat(getImportedConfigBeans(context)).containsExactly(
+							"ConfigA", "ConfigB", "ConfigC", "ConfigD");
+				});
+	}
+
+	@Test
+	public void multipleSelectorWithRedundantImportsShouldMergeAndSortCorrectly() {
+		this.contextRunner.withUserConfiguration(SingleConfig.class, Config.class,
+				AnotherConfig.class).run((context) -> {
+			assertThat(getImportedConfigBeans(context)).containsExactly(
+					"ConfigA", "ConfigB", "ConfigC", "ConfigD");
+		});
+	}
+
+	private List<String> getImportedConfigBeans(AssertableApplicationContext context) {
+		String shortName = ClassUtils.getShortName(
+				AutoConfigurationImportSelectorIntegrationTests.class);
+		int beginIndex = shortName.length() + 1;
+		List<String> orderedConfigBeans = new ArrayList<>();
+		for (String bean : context.getBeanDefinitionNames()) {
+			if (bean.contains("$Config")) {
+				String shortBeanName = ClassUtils.getShortName(bean);
+				orderedConfigBeans.add(shortBeanName.substring(beginIndex));
+			}
+		}
+		return orderedConfigBeans;
+	}
+
+	@ImportAutoConfiguration
+	static class NoConfig {
+
+	}
+
+	@ImportAutoConfiguration(ConfigC.class)
+	static class SingleConfig {
+
+	}
+
+	@ImportAutoConfiguration({ ConfigD.class, ConfigB.class })
+	static class Config {
+
+	}
+
+	@ImportAutoConfiguration({ ConfigC.class, ConfigA.class })
+	static class AnotherConfig {
+
+	}
+
+
+	@Configuration
+	static class ConfigA {
+
+	}
+
+	@Configuration
+	@AutoConfigureAfter(ConfigA.class)
+	@AutoConfigureBefore(ConfigC.class)
+	static class ConfigB {
+
+	}
+
+	@Configuration
+	static class ConfigC {
+
+	}
+
+	@Configuration
+	@AutoConfigureAfter(ConfigC.class)
+	static class ConfigD {
+
+	}
+
+}