Refine ImportsContextCustomizer cache logic

Update `ImportsContextCustomizer` so that whenever possible a more
specific cache key is used.

Prior to this commit the customizer would generate a key based on *all*
annotations on the test class. This has repeatedly caused issues where
test classes that should have the same cache key did not due to
unrelated annotations.

A new `DeterminableImports` interface has been added that can be
implemented by `ImportSelector` and `ImportBeanDefinitionRegistrar`
implementations that are able to determine their imports early. The
existing `ImportAutoConfigurationImportSelector` and
`AutoConfigurationPackages` classes have been retrofitted with
this interface.

Fixes gh-7953

spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/cache/ImportsContextCustomizerFactoryWithAutoConfigurationTests.java

@@ -0,0 +1,158 @@
+/*
+ * Copyright 2012-2017 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.test.autoconfigure.cache;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+import org.junit.Test;
+import org.junit.runner.notification.RunNotifier;
+import org.junit.runners.model.InitializationError;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.ImportAutoConfiguration;
+import org.springframework.boot.autoconfigure.domain.EntityScan;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.boot.test.autoconfigure.orm.jpa.ExampleEntity;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@code ImportsContextCustomizerFactory} when used with
+ * {@link ImportAutoConfiguration}.
+ *
+ * @author Phillip Webb
+ * @author Andy Wilkinson
+ */
+public class ImportsContextCustomizerFactoryWithAutoConfigurationTests {
+
+	static ApplicationContext contextFromTest;
+
+	@Test
+	public void testClassesThatHaveSameAnnotationsShareAContext()
+			throws InitializationError {
+		RunNotifier notifier = new RunNotifier();
+		new SpringJUnit4ClassRunner(DataJpaTest1.class).run(notifier);
+		ApplicationContext test1Context = contextFromTest;
+		new SpringJUnit4ClassRunner(DataJpaTest3.class).run(notifier);
+		ApplicationContext test2Context = contextFromTest;
+		assertThat(test1Context).isSameAs(test2Context);
+	}
+
+	@Test
+	public void testClassesThatOnlyHaveDifferingUnrelatedAnnotationsShareAContext()
+			throws InitializationError {
+		RunNotifier notifier = new RunNotifier();
+		new SpringJUnit4ClassRunner(DataJpaTest1.class).run(notifier);
+		ApplicationContext test1Context = contextFromTest;
+		new SpringJUnit4ClassRunner(DataJpaTest2.class).run(notifier);
+		ApplicationContext test2Context = contextFromTest;
+		assertThat(test1Context).isSameAs(test2Context);
+	}
+
+	@Test
+	public void testClassesThatOnlyHaveDifferingPropertyMappedAnnotationAttributesDoNotShareAContext()
+			throws InitializationError {
+		RunNotifier notifier = new RunNotifier();
+		new SpringJUnit4ClassRunner(DataJpaTest1.class).run(notifier);
+		ApplicationContext test1Context = contextFromTest;
+		new SpringJUnit4ClassRunner(DataJpaTest4.class).run(notifier);
+		ApplicationContext test2Context = contextFromTest;
+		assertThat(test1Context).isNotSameAs(test2Context);
+	}
+
+	@DataJpaTest
+	@ContextConfiguration(classes = EmptyConfig.class)
+	@Unrelated1
+	public static class DataJpaTest1 {
+
+		@Autowired
+		private ApplicationContext context;
+
+		@Test
+		public void test() {
+			contextFromTest = this.context;
+		}
+
+	}
+
+	@ContextConfiguration(classes = EmptyConfig.class)
+	@DataJpaTest
+	@Unrelated2
+	public static class DataJpaTest2 {
+
+		@Autowired
+		private ApplicationContext context;
+
+		@Test
+		public void test() {
+			contextFromTest = this.context;
+		}
+
+	}
+
+	@ContextConfiguration(classes = EmptyConfig.class)
+	@DataJpaTest
+	@Unrelated1
+	public static class DataJpaTest3 {
+
+		@Autowired
+		private ApplicationContext context;
+
+		@Test
+		public void test() {
+			contextFromTest = this.context;
+		}
+
+	}
+
+	@ContextConfiguration(classes = EmptyConfig.class)
+	@DataJpaTest(showSql = false)
+	@Unrelated1
+	public static class DataJpaTest4 {
+
+		@Autowired
+		private ApplicationContext context;
+
+		@Test
+		public void test() {
+			contextFromTest = this.context;
+		}
+
+	}
+
+	@Retention(RetentionPolicy.RUNTIME)
+	static @interface Unrelated1 {
+
+	}
+
+	@Retention(RetentionPolicy.RUNTIME)
+	static @interface Unrelated2 {
+
+	}
+
+	@Configuration
+	@EntityScan(basePackageClasses = ExampleEntity.class)
+	static class EmptyConfig {
+
+	}
+
+}