Optimize CacheKey handling for immutable sources

Update `SpringIterableConfigurationPropertySource` so that cache keys
do not need to be checked if property sources are immutable.

See gh-16717

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/SpringIterableConfigurationPropertySource.java

@@ -25,6 +25,7 @@
 import java.util.Set;
 import java.util.stream.Stream;
 
+import org.springframework.boot.env.OriginTrackedMapPropertySource;
 import org.springframework.core.env.EnumerablePropertySource;
 import org.springframework.core.env.MapPropertySource;
 import org.springframework.core.env.PropertySource;
@@ -192,21 +193,37 @@ private static final class CacheKey {
 
 		private final Object key;
 
-		private CacheKey(Object key) {
+		private final int size;
+
+		private final boolean unmodifiableKey;
+
+		private CacheKey(Object key, boolean unmodifiableKey) {
 			this.key = key;
+			this.size = calculateSize(key);
+			this.unmodifiableKey = unmodifiableKey;
 		}
 
 		public CacheKey copy() {
-			return new CacheKey(copyKey(this.key));
+			return new CacheKey(copyKey(this.key), this.unmodifiableKey);
 		}
 
 		private Object copyKey(Object key) {
+			if (this.unmodifiableKey) {
+				return key;
+			}
 			if (key instanceof Set) {
 				return new HashSet<Object>((Set<?>) key);
 			}
 			return ((String[]) key).clone();
 		}
 
+		private int calculateSize(Object key) {
+			if (key instanceof Set) {
+				return ((Set<?>) key).size();
+			}
+			return ((String[]) key).length;
+		}
+
 		@Override
 		public boolean equals(Object obj) {
 			if (this == obj) {
@@ -215,7 +232,11 @@ public boolean equals(Object obj) {
 			if (obj == null || getClass() != obj.getClass()) {
 				return false;
 			}
-			return ObjectUtils.nullSafeEquals(this.key, ((CacheKey) obj).key);
+			CacheKey otherCacheKey = (CacheKey) obj;
+			if (this.size != otherCacheKey.size) {
+				return false;
+			}
+			return ObjectUtils.nullSafeEquals(this.key, otherCacheKey.key);
 		}
 
 		@Override
@@ -225,9 +246,10 @@ public int hashCode() {
 
 		public static CacheKey get(EnumerablePropertySource<?> source) {
 			if (source instanceof MapPropertySource) {
-				return new CacheKey(((MapPropertySource) source).getSource().keySet());
+				return new CacheKey(((MapPropertySource) source).getSource().keySet(),
+						source instanceof OriginTrackedMapPropertySource);
 			}
-			return new CacheKey(source.getPropertyNames());
+			return new CacheKey(source.getPropertyNames(), false);
 		}
 
 	}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/source/SpringIterableConfigurationPropertySourceTests.java

@@ -25,6 +25,7 @@
 
 import org.junit.Test;
 
+import org.springframework.boot.env.OriginTrackedMapPropertySource;
 import org.springframework.boot.origin.Origin;
 import org.springframework.boot.origin.OriginLookup;
 import org.springframework.core.env.EnumerablePropertySource;
@@ -160,7 +161,7 @@ public void containsDescendantOfShouldCheckSourceNames() {
 	}
 
 	@Test
-	public void propertySourceKeyDataChangeInvalidatesCache() {
+	public void simpleMapPropertySourceKeyDataChangeInvalidatesCache() {
 		// gh-13344
 		Map<String, Object> map = new LinkedHashMap<>();
 		map.put("key1", "value1");
@@ -184,6 +185,18 @@ public void concurrentModificationExceptionInvalidatesCache() {
 				source, DefaultPropertyMapper.INSTANCE);
 		assertThat(adapter.stream().count()).isEqualTo(2);
 		map.setThrowException(true);
+	}
+
+	public void originTrackedMapPropertySourceKeyAdditionInvalidatesCache() {
+		// gh-13344
+		Map<String, Object> map = new LinkedHashMap<>();
+		map.put("key1", "value1");
+		map.put("key2", "value2");
+		EnumerablePropertySource<?> source = new OriginTrackedMapPropertySource("test",
+				map);
+		SpringIterableConfigurationPropertySource adapter = new SpringIterableConfigurationPropertySource(
+				source, DefaultPropertyMapper.INSTANCE);
+		assertThat(adapter.stream().count()).isEqualTo(2);
 		map.put("key3", "value3");
 		assertThat(adapter.stream().count()).isEqualTo(3);
 	}