Merge pull request #48962 from junpakPark

* pr/48962:
  Polish "Document properties whose default values have changed"
  Document properties whose default values have changed

Closes gh-48962

configuration-metadata/spring-boot-configuration-metadata-changelog-generator/src/main/java/org/springframework/boot/configurationmetadata/changelog/ChangelogWriter.java

@@ -68,6 +68,8 @@ class ChangelogWriter implements AutoCloseable {
 		String newVersionNumber = changelog.newVersionNumber();
 		Map<DifferenceType, List<Difference>> differencesByType = collateByType(changelog);
 		write("Configuration property changes between `%s` and `%s`%n", oldVersionNumber, newVersionNumber);
+		write("%n%n%n== Default Changed in %s%n%n", newVersionNumber);
+		writeDefaultChanged(differencesByType.get(DifferenceType.DEFAULT_CHANGED));
 		write("%n%n%n== Deprecated in %s%n%n", newVersionNumber);
 		writeDeprecated(differencesByType.get(DifferenceType.DEPRECATED));
 		write("%n%n%n== Added in %s%n%n", newVersionNumber);
@@ -98,6 +100,17 @@ class ChangelogWriter implements AutoCloseable {
 		writeDeprecatedPropertyRow(difference.newProperty());
 	}
 
+	private void writeDefaultChanged(List<Difference> differences) {
+		List<Difference> rows = sortProperties(differences, Difference::newProperty);
+		writeTable("| Key | Old Default | New Default", rows, this::writeDefaultChanged);
+	}
+
+	private void writeDefaultChanged(Difference difference) {
+		writeCell(monospace(difference.newProperty().getId()));
+		writeCell(monospace(asString(difference.oldProperty().getDefaultValue())));
+		writeCell(monospace(asString(difference.newProperty().getDefaultValue())));
+	}
+
 	private void writeAdded(List<Difference> differences) {
 		List<Difference> rows = sortProperties(differences, Difference::newProperty);
 		writeTable("| Key | Default value | Description", rows, this::writeAdded);

configuration-metadata/spring-boot-configuration-metadata-changelog-generator/src/main/java/org/springframework/boot/configurationmetadata/changelog/Difference.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.configurationmetadata.changelog;
 
+import java.util.Objects;
+
 import org.springframework.boot.configurationmetadata.ConfigurationMetadataProperty;
 import org.springframework.boot.configurationmetadata.Deprecation.Level;
 
@@ -49,6 +51,9 @@ record Difference(DifferenceType type, ConfigurationMetadataProperty oldProperty
 				&& newProperty.isDeprecated() && newProperty.getDeprecation().getLevel() == Level.ERROR) {
 			return new Difference(DifferenceType.DELETED, oldProperty, newProperty);
 		}
+		if (!Objects.equals(oldProperty.getDefaultValue(), newProperty.getDefaultValue())) {
+			return new Difference(DifferenceType.DEFAULT_CHANGED, oldProperty, newProperty);
+		}
 		return null;
 	}
 

configuration-metadata/spring-boot-configuration-metadata-changelog-generator/src/main/java/org/springframework/boot/configurationmetadata/changelog/DifferenceType.java

@@ -37,6 +37,12 @@ enum DifferenceType {
 	/**
 	 * The entry has been deleted.
 	 */
-	DELETED
+	DELETED,
+
+	/**
+	 * The entry's default value has changed. The entry exists in both the previous and
+	 * current versions, but its default value is different.
+	 */
+	DEFAULT_CHANGED
 
 }

configuration-metadata/spring-boot-configuration-metadata-changelog-generator/src/test/java/org/springframework/boot/configurationmetadata/changelog/ChangelogTests.java

@@ -39,7 +39,7 @@ class ChangelogTests {
 		assertThat(differences).isNotNull();
 		assertThat(differences.oldVersionNumber()).isEqualTo("1.0");
 		assertThat(differences.newVersionNumber()).isEqualTo("2.0");
-		assertThat(differences.differences()).hasSize(7);
+		assertThat(differences.differences()).hasSize(9);
 		List<Difference> added = differences.differences()
 			.stream()
 			.filter((difference) -> difference.type() == DifferenceType.ADDED)
@@ -65,12 +65,20 @@ class ChangelogTests {
 		assertThat(deprecated).hasSize(1);
 		assertProperty(deprecated.get(0).oldProperty(), "test.deprecate", String.class, "wrong");
 		assertProperty(deprecated.get(0).newProperty(), "test.deprecate", String.class, "wrong");
+		List<Difference> defaultChanged = differences.differences()
+			.stream()
+			.filter((difference) -> difference.type() == DifferenceType.DEFAULT_CHANGED)
+			.toList();
+		assertThat(defaultChanged).hasSize(2)
+			.anySatisfy((entry) -> assertProperty(entry.newProperty(), "test.default.array.change", String[].class,
+					new String[] { "b", "a" }))
+			.anySatisfy((entry) -> assertProperty(entry.newProperty(), "test.default.change", String.class, "new"));
 	}
 
 	private void assertProperty(ConfigurationMetadataProperty property, String id, Class<?> type, Object defaultValue) {
 		assertThat(property).isNotNull();
 		assertThat(property.getId()).isEqualTo(id);
-		assertThat(property.getType()).isEqualTo(type.getName());
+		assertThat(property.getType()).isEqualTo(type.getCanonicalName());
 		assertThat(property.getDefaultValue()).isEqualTo(defaultValue);
 	}
 

configuration-metadata/spring-boot-configuration-metadata-changelog-generator/src/test/resources/sample-1.0.json

@@ -6,6 +6,18 @@
       "description": "Test equality.",
       "defaultValue": "test"
     },
+    {
+      "name": "test.default.change",
+      "type": "java.lang.String",
+      "description": "Test default value change.",
+      "defaultValue": "old"
+    },
+    {
+      "name": "test.default.array.change",
+      "type": "java.lang.String[]",
+      "description": "Test default array value change.",
+      "defaultValue": ["a", "b"]
+    },
     {
       "name": "test.replace",
       "type": "java.lang.String",

configuration-metadata/spring-boot-configuration-metadata-changelog-generator/src/test/resources/sample-2.0.json

@@ -6,6 +6,18 @@
       "description": "Test add.",
       "defaultValue": "new"
     },
+    {
+      "name": "test.default.change",
+      "type": "java.lang.String",
+      "description": "Test default value change.",
+      "defaultValue": "new"
+    },
+    {
+      "name": "test.default.array.change",
+      "type": "java.lang.String[]",
+      "description": "Test default array value change.",
+      "defaultValue": ["b", "a"]
+    },
     {
       "name": "test.replace",
       "type": "java.lang.String",

configuration-metadata/spring-boot-configuration-metadata-changelog-generator/src/test/resources/sample.adoc

@@ -2,6 +2,22 @@ Configuration property changes between `1.0` and `2.0`
 
 
 
+== Default Changed in 2.0
+
+|======================
+| Key | Old Default | New Default
+
+| `test.default.array.change`
+| `a, b`
+| `b, a`
+
+| `test.default.change`
+| `old`
+| `new`
+|======================
+
+
+
 == Deprecated in 2.0
 
 |======================