Fix equals when adapt removes trailing characters from element

Closes gh-30317

Author: wilkinsona

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

@@ -448,7 +448,7 @@ private boolean defaultElementEquals(Elements e1, Elements e2, int i) {
 		int i2 = 0;
 		while (i1 < l1) {
 			if (i2 >= l2) {
-				return false;
+				return remainderIsNotAlphaNumberic(e1, i, i1);
 			}
 			char ch1 = indexed1 ? e1.charAt(i, i1) : Character.toLowerCase(e1.charAt(i, i1));
 			char ch2 = indexed2 ? e2.charAt(i, i2) : Character.toLowerCase(e2.charAt(i, i2));
@@ -467,17 +467,23 @@ else if (ch1 != ch2) {
 			}
 		}
 		if (i2 < l2) {
-			if (indexed2) {
+			return remainderIsNotAlphaNumberic(e2, i, i2);
+		}
+		return true;
+	}
+
+	private boolean remainderIsNotAlphaNumberic(Elements elements, int element, int index) {
+		if (elements.getType(element).isIndexed()) {
+			return false;
+		}
+		int length = elements.getLength(element);
+		do {
+			char c = Character.toLowerCase(elements.charAt(element, index++));
+			if (ElementsParser.isAlphaNumeric(c)) {
 				return false;
 			}
-			do {
-				char ch2 = Character.toLowerCase(e2.charAt(i, i2++));
-				if (ElementsParser.isAlphaNumeric(ch2)) {
-					return false;
-				}
-			}
-			while (i2 < l2);
 		}
+		while (index < length);
 		return true;
 	}
 

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

@@ -685,6 +685,15 @@ void equalsWhenNameStartsTheSameUsingDashedCompare() {
 		assertThat(n2).isNotEqualTo(n1);
 	}
 
+	@Test
+	void equalsWhenAdaptedNameMatchesDueToRemovalOfTrailingCharacters() {
+		// gh-30317
+		ConfigurationPropertyName name1 = ConfigurationPropertyName.of("example.demo");
+		ConfigurationPropertyName name2 = ConfigurationPropertyName.adapt("example.demo$$", '.');
+		assertThat(name1).isEqualTo(name2);
+		assertThat(name2).isEqualTo(name1);
+	}
+
 	@Test
 	void isValidWhenValidShouldReturnTrue() {
 		assertThat(ConfigurationPropertyName.isValid("")).isTrue();