Add support for ImportAware callback

This commit adds a way for a BeanFactoryPostProcessor to participate to
AOT optimizations by contributing code that replaces its runtime
behaviour.

ConfigurationClassPostProcessor does implement this new interface and
computes a mapping of the ImportAware configuration classes. The mapping
is generated for latter reuse by ImportAwareAotBeanPostProcessor.

Closes gh-2811

spring-context/src/test/java/org/springframework/context/annotation/ImportAwareAotBeanPostProcessorTests.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2002-2022 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 org.springframework.context.annotation;
+
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.core.type.AnnotationMetadata;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+
+/**
+ * Tests for {@link ImportAwareAotBeanPostProcessor}.
+ *
+ * @author Stephane Nicoll
+ */
+class ImportAwareAotBeanPostProcessorTests {
+
+	@Test
+	void postProcessOnMatchingCandidate() {
+		ImportAwareAotBeanPostProcessor postProcessor = new ImportAwareAotBeanPostProcessor(
+				Map.of(TestImportAware.class.getName(), ImportAwareAotBeanPostProcessorTests.class.getName()));
+		TestImportAware importAware = new TestImportAware();
+		postProcessor.postProcessBeforeInitialization(importAware, "test");
+		assertThat(importAware.importMetadata).isNotNull();
+		assertThat(importAware.importMetadata.getClassName())
+				.isEqualTo(ImportAwareAotBeanPostProcessorTests.class.getName());
+	}
+
+	@Test
+	void postProcessOnMatchingCandidateWithNestedClass() {
+		ImportAwareAotBeanPostProcessor postProcessor = new ImportAwareAotBeanPostProcessor(
+				Map.of(TestImportAware.class.getName(), TestImporting.class.getName()));
+		TestImportAware importAware = new TestImportAware();
+		postProcessor.postProcessBeforeInitialization(importAware, "test");
+		assertThat(importAware.importMetadata).isNotNull();
+		assertThat(importAware.importMetadata.getClassName())
+				.isEqualTo(TestImporting.class.getName());
+	}
+
+	@Test
+	void postProcessOnNoCandidateDoesNotInvokeCallback() {
+		ImportAwareAotBeanPostProcessor postProcessor = new ImportAwareAotBeanPostProcessor(
+				Map.of(String.class.getName(), ImportAwareAotBeanPostProcessorTests.class.getName()));
+		TestImportAware importAware = new TestImportAware();
+		postProcessor.postProcessBeforeInitialization(importAware, "test");
+		assertThat(importAware.importMetadata).isNull();
+	}
+
+	@Test
+	void postProcessOnMatchingCandidateWithNoMetadata() {
+		ImportAwareAotBeanPostProcessor postProcessor = new ImportAwareAotBeanPostProcessor(
+				Map.of(TestImportAware.class.getName(), "com.example.invalid.DoesNotExist"));
+		TestImportAware importAware = new TestImportAware();
+		assertThatIllegalStateException().isThrownBy(() -> postProcessor.postProcessBeforeInitialization(importAware, "test"))
+				.withMessageContaining("Failed to read metadata for 'com.example.invalid.DoesNotExist'");
+	}
+
+
+	static class TestImportAware implements ImportAware {
+
+		private AnnotationMetadata importMetadata;
+
+		@Override
+		public void setImportMetadata(AnnotationMetadata importMetadata) {
+			this.importMetadata = importMetadata;
+		}
+	}
+
+	static class TestImporting {
+
+	}
+
+}

spring-context/src/test/java/org/springframework/context/annotation/ImportAwareBeanFactoryContributionTests.java

@@ -0,0 +1,115 @@
+/*
+ * Copyright 2002-2022 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 org.springframework.context.annotation;
+
+import java.io.IOException;
+import java.io.StringWriter;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.aot.generator.DefaultGeneratedTypeContext;
+import org.springframework.aot.generator.GeneratedType;
+import org.springframework.aot.generator.GeneratedTypeContext;
+import org.springframework.beans.factory.generator.BeanFactoryContribution;
+import org.springframework.beans.factory.generator.BeanFactoryInitialization;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.beans.factory.support.RootBeanDefinition;
+import org.springframework.beans.testfixture.beans.factory.generator.SimpleConfiguration;
+import org.springframework.context.testfixture.context.generator.annotation.ImportConfiguration;
+import org.springframework.javapoet.ClassName;
+import org.springframework.javapoet.support.CodeSnippet;
+import org.springframework.lang.Nullable;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@code ImportAwareBeanFactoryConfiguration}.
+ *
+ * @author Stephane Nicoll
+ */
+public class ImportAwareBeanFactoryContributionTests {
+
+	@Test
+	void contributeWithImportAwareConfigurationRegistersBeanPostProcessor() {
+		BeanFactoryContribution contribution = createContribution(ImportConfiguration.class);
+		assertThat(contribution).isNotNull();
+		BeanFactoryInitialization initialization = new BeanFactoryInitialization(createGenerationContext());
+		contribution.applyTo(initialization);
+		assertThat(CodeSnippet.of(initialization.toCodeBlock()).getSnippet()).isEqualTo("""
+				beanFactory.addBeanPostProcessor(createImportAwareBeanPostProcessor());
+				""");
+	}
+
+	@Test
+	void contributeWithImportAwareConfigurationCreateMappingsMethod() {
+		BeanFactoryContribution contribution = createContribution(ImportConfiguration.class);
+		assertThat(contribution).isNotNull();
+		GeneratedTypeContext generationContext = createGenerationContext();
+		contribution.applyTo(new BeanFactoryInitialization(generationContext));
+		assertThat(codeOf(generationContext.getMainGeneratedType())).contains("""
+					private ImportAwareAotBeanPostProcessor createImportAwareBeanPostProcessor() {
+						Map<String, String> mappings = new HashMap<>();
+						mappings.put("org.springframework.context.testfixture.context.generator.annotation.ImportAwareConfiguration", "org.springframework.context.testfixture.context.generator.annotation.ImportConfiguration");
+						return new ImportAwareAotBeanPostProcessor(mappings);
+					}
+				""");
+
+	}
+
+	@Test
+	void contributeWithImportAwareConfigurationRegisterBytecodeResourceHint() {
+		BeanFactoryContribution contribution = createContribution(ImportConfiguration.class);
+		assertThat(contribution).isNotNull();
+		GeneratedTypeContext generationContext = createGenerationContext();
+		contribution.applyTo(new BeanFactoryInitialization(generationContext));
+		assertThat(generationContext.runtimeHints().resources().resourcePatterns())
+				.singleElement().satisfies(resourceHint -> assertThat(resourceHint.getIncludes()).containsOnly(
+						"org/springframework/context/testfixture/context/generator/annotation/ImportConfiguration.class"));
+	}
+
+	@Test
+	void contributeWithNoImportAwareConfigurationReturnsNull() {
+		assertThat(createContribution(SimpleConfiguration.class)).isNull();
+	}
+
+
+	@Nullable
+	private BeanFactoryContribution createContribution(Class<?> type) {
+		DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
+		beanFactory.registerBeanDefinition("configuration", new RootBeanDefinition(type));
+		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
+		pp.postProcessBeanFactory(beanFactory);
+		return pp.contribute(beanFactory);
+	}
+
+	private GeneratedTypeContext createGenerationContext() {
+		return new DefaultGeneratedTypeContext("com.example", packageName ->
+				GeneratedType.of(ClassName.get(packageName, "Test")));
+	}
+
+	private String codeOf(GeneratedType type) {
+		try {
+			StringWriter out = new StringWriter();
+			type.toJavaFile().writeTo(out);
+			return out.toString();
+		}
+		catch (IOException ex) {
+			throw new IllegalStateException(ex);
+		}
+	}
+
+}