Polish "Allow to exclude an empty set of ErrorAttributes"

See gh-24230

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/error/ErrorAttributeOptions.java

@@ -27,7 +27,6 @@ import java.util.Set;
  *
  * @author Scott Frederick
  * @author Phillip Webb
- * @author Wanderlei Souza
  * @since 2.3.0
  */
 public final class ErrorAttributeOptions {
@@ -64,8 +63,7 @@ public final class ErrorAttributeOptions {
 	 * @return an {@code ErrorAttributeOptions}
 	 */
 	public ErrorAttributeOptions including(Include... includes) {
-		EnumSet<Include> updated = (this.includes.isEmpty()) ? EnumSet.noneOf(Include.class)
-				: EnumSet.copyOf(this.includes);
+		EnumSet<Include> updated = copyIncludes();
 		updated.addAll(Arrays.asList(includes));
 		return new ErrorAttributeOptions(Collections.unmodifiableSet(updated));
 	}
@@ -77,12 +75,15 @@ public final class ErrorAttributeOptions {
 	 * @return an {@code ErrorAttributeOptions}
 	 */
 	public ErrorAttributeOptions excluding(Include... excludes) {
-		EnumSet<Include> updated = (this.includes.isEmpty()) ? EnumSet.noneOf(Include.class)
-				: EnumSet.copyOf(this.includes);
+		EnumSet<Include> updated = copyIncludes();
 		updated.removeAll(Arrays.asList(excludes));
 		return new ErrorAttributeOptions(Collections.unmodifiableSet(updated));
 	}
 
+	private EnumSet<Include> copyIncludes() {
+		return (this.includes.isEmpty()) ? EnumSet.noneOf(Include.class) : EnumSet.copyOf(this.includes);
+	}
+
 	/**
 	 * Create an {@code ErrorAttributeOptions} with defaults.
 	 * @return an {@code ErrorAttributeOptions}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/error/ErrorAttributesOptionsTests.java

@@ -16,36 +16,46 @@
 
 package org.springframework.boot.web.servlet.error;
 
-import static org.assertj.core.api.Assertions.assertThat;
-
 import java.util.EnumSet;
-import java.util.Set;
 
 import org.junit.jupiter.api.Test;
+
 import org.springframework.boot.web.error.ErrorAttributeOptions;
 import org.springframework.boot.web.error.ErrorAttributeOptions.Include;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
- * Tests for {@link ErrorAttributesOptions}.
+ * Tests for {@link ErrorAttributeOptions}.
  *
  * @author Wanderlei Souza
+ * @author Stephane Nicoll
  */
 class ErrorAttributesOptionsTests {
 
 	@Test
-	void excludingFromEmptySetWithoutErrors() {
-		Set<Include> includes = EnumSet.noneOf(Include.class);
-		ErrorAttributeOptions errorAttributeOptions = ErrorAttributeOptions.of(includes);
-		errorAttributeOptions = errorAttributeOptions.excluding(Include.EXCEPTION);
-		assertThat(errorAttributeOptions.getIncludes().isEmpty());
+	void includingFromEmptyAttributesReturnAddedEntry() {
+		ErrorAttributeOptions options = ErrorAttributeOptions.of(EnumSet.noneOf(Include.class));
+		assertThat(options.including(Include.EXCEPTION).getIncludes()).containsOnly(Include.EXCEPTION);
+	}
+
+	@Test
+	void includingFromMatchingAttributesDoesNotModifyOptions() {
+		ErrorAttributeOptions options = ErrorAttributeOptions.of(EnumSet.of(Include.EXCEPTION, Include.STACK_TRACE));
+		assertThat(options.including(Include.EXCEPTION).getIncludes()).containsOnly(Include.EXCEPTION,
+				Include.STACK_TRACE);
+	}
+
+	@Test
+	void excludingFromEmptyAttributesReturnEmptyList() {
+		ErrorAttributeOptions options = ErrorAttributeOptions.of(EnumSet.noneOf(Include.class));
+		assertThat(options.excluding(Include.EXCEPTION).getIncludes()).isEmpty();
 	}
-	
+
 	@Test
-	void includingInEmptySetWithoutErrors() {
-		Set<Include> includes = EnumSet.noneOf(Include.class);
-		ErrorAttributeOptions errorAttributeOptions = ErrorAttributeOptions.of(includes);
-		errorAttributeOptions = errorAttributeOptions.including(Include.EXCEPTION);
-		assertThat(errorAttributeOptions.getIncludes().isEmpty());
+	void excludingFromMatchingAttributesRemoveMatch() {
+		ErrorAttributeOptions options = ErrorAttributeOptions.of(EnumSet.of(Include.EXCEPTION, Include.STACK_TRACE));
+		assertThat(options.excluding(Include.EXCEPTION).getIncludes()).containsOnly(Include.STACK_TRACE);
 	}
 
 }