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/src/test/java/org/springframework/boot/test/context/ImportsContextCustomizerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2016 the original author or authors.
+ * 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.
@@ -16,10 +16,21 @@
 
 package org.springframework.boot.test.context;
 
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.util.Collections;
+import java.util.Set;
+
 import kotlin.Metadata;
 import org.junit.Test;
 import org.spockframework.runtime.model.SpecMetadata;
 
+import org.springframework.boot.context.annotation.DeterminableImports;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.context.annotation.ImportSelector;
+import org.springframework.core.type.AnnotationMetadata;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
@@ -29,6 +40,26 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 public class ImportsContextCustomizerTests {
 
+	@Test
+	public void importSelectorsCouldUseAnyAnnotations() throws Exception {
+		assertThat(new ImportsContextCustomizer(FirstImportSelectorAnnotatedClass.class))
+				.isNotEqualTo(new ImportsContextCustomizer(
+						SecondImportSelectorAnnotatedClass.class));
+	}
+
+	@Test
+	public void determinableImportSelector() throws Exception {
+		assertThat(new ImportsContextCustomizer(
+				FirstDeterminableImportSelectorAnnotatedClass.class))
+						.isEqualTo(new ImportsContextCustomizer(
+								SecondDeterminableImportSelectorAnnotatedClass.class));
+	}
+
+	@Test
+	public void importAutoConfigurationCanIgnoreAdditionalAnnotations() throws Exception {
+
+	}
+
 	@Test
 	public void customizersForTestClassesWithDifferentKotlinMetadataAreEqual() {
 		assertThat(new ImportsContextCustomizer(FirstKotlinAnnotatedTestClass.class))
@@ -43,6 +74,30 @@ public class ImportsContextCustomizerTests {
 						SecondSpockAnnotatedTestClass.class));
 	}
 
+	@Import(TestImportSelector.class)
+	@Indicator1
+	static class FirstImportSelectorAnnotatedClass {
+
+	}
+
+	@Import(TestImportSelector.class)
+	@Indicator2
+	static class SecondImportSelectorAnnotatedClass {
+
+	}
+
+	@Import(TestDeterminableImportSelector.class)
+	@Indicator1
+	static class FirstDeterminableImportSelectorAnnotatedClass {
+
+	}
+
+	@Import(TestDeterminableImportSelector.class)
+	@Indicator2
+	static class SecondDeterminableImportSelectorAnnotatedClass {
+
+	}
+
 	@Metadata(d2 = "foo")
 	static class FirstKotlinAnnotatedTestClass {
 
@@ -63,4 +118,43 @@ public class ImportsContextCustomizerTests {
 
 	}
 
+	@Retention(RetentionPolicy.RUNTIME)
+	@interface Indicator1 {
+
+	}
+
+	@Retention(RetentionPolicy.RUNTIME)
+	@interface Indicator2 {
+
+	}
+
+	static class TestImportSelector implements ImportSelector {
+
+		@Override
+		public String[] selectImports(AnnotationMetadata arg0) {
+			return new String[] {};
+		}
+
+	}
+
+	static class TestDeterminableImportSelector
+			implements ImportSelector, DeterminableImports {
+
+		@Override
+		public String[] selectImports(AnnotationMetadata arg0) {
+			return new String[] { TestConfig.class.getName() };
+		}
+
+		@Override
+		public Set<Object> determineImports(AnnotationMetadata metadata) {
+			return Collections.<Object>singleton(TestConfig.class.getName());
+		}
+
+	}
+
+	@Configuration
+	static class TestConfig {
+
+	}
+
 }