Protect against stack overflow when searching meta annotations

It is legal for an annotation to be annotated with itself. Previously,
when searching for meta annotations this could lead to a stack overflow.
This was likely to occur when using Kotlin as, like Java, its Target
annotation is annotated with itself. A stack overflow doesn’t occur
with Java’s Target annotation due to some short-circuiting logic for
annotations in java.lang.

This commit updates the logic for finding meta-annotations to
short-circuit when an annotation that has already been seen is
encountered.

Closes gh-5902

spring-boot-test/src/test/java/org/springframework/boot/test/context/ImportsContextCustomizerFactoryTests.java

@@ -37,6 +37,7 @@ import static org.mockito.Mockito.mock;
  * Tests for {@link ImportsContextCustomizerFactory} and {@link ImportsContextCustomizer}.
  *
  * @author Phillip Webb
+ * @author Andy Wilkinson
  */
 public class ImportsContextCustomizerFactoryTests {
 
@@ -101,6 +102,12 @@ public class ImportsContextCustomizerFactoryTests {
 		assertThat(context.getBean(ImportedBean.class)).isNotNull();
 	}
 
+	@Test
+	public void selfAnnotatingAnnotationDoesNotCauseStackOverflow() {
+		assertThat(this.factory.createContextCustomizer(
+				TestWithImportAndSelfAnnotatingAnnotation.class, null)).isNotNull();
+	}
+
 	static class TestWithNoImport {
 
 	}
@@ -137,6 +144,12 @@ public class ImportsContextCustomizerFactoryTests {
 
 	}
 
+	@SelfAnnotating
+	@Import(ImportedBean.class)
+	static class TestWithImportAndSelfAnnotatingAnnotation {
+
+	}
+
 	@Retention(RetentionPolicy.RUNTIME)
 	@Import(ImportedBean.class)
 	@interface MetaImport {
@@ -153,4 +166,10 @@ public class ImportsContextCustomizerFactoryTests {
 
 	}
 
+	@Retention(RetentionPolicy.RUNTIME)
+	@SelfAnnotating
+	static @interface SelfAnnotating {
+
+	}
+
 }