Fix subName from adapted name with value processor

Previously, when a configuration property name was created by
adapting a source with a value processor, creating sub names from
that property name did not work correctly. This broke binding of
prefixed environment variables to a map as the ancestor checking
did not work.

Fixes gh-43304

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

@@ -773,7 +773,7 @@ public final class ConfigurationPropertyName implements Comparable<Configuration
 			ElementType[] type = new ElementType[size];
 			System.arraycopy(this.type, 0, type, 0, this.size);
 			System.arraycopy(additional.type, 0, type, this.size, additional.size);
-			CharSequence[] resolved = newResolved(size);
+			CharSequence[] resolved = newResolved(0, size);
 			for (int i = 0; i < additional.size; i++) {
 				resolved[this.size + i] = additional.get(i);
 			}
@@ -781,13 +781,13 @@ public final class ConfigurationPropertyName implements Comparable<Configuration
 		}
 
 		Elements chop(int size) {
-			CharSequence[] resolved = newResolved(size);
+			CharSequence[] resolved = newResolved(0, size);
 			return new Elements(this.source, size, this.start, this.end, this.type, resolved);
 		}
 
 		Elements subElements(int offset) {
 			int size = this.size - offset;
-			CharSequence[] resolved = newResolved(size);
+			CharSequence[] resolved = newResolved(offset, size);
 			int[] start = new int[size];
 			System.arraycopy(this.start, offset, start, 0, size);
 			int[] end = new int[size];
@@ -797,10 +797,10 @@ public final class ConfigurationPropertyName implements Comparable<Configuration
 			return new Elements(this.source, size, start, end, type, resolved);
 		}
 
-		private CharSequence[] newResolved(int size) {
+		private CharSequence[] newResolved(int offset, int size) {
 			CharSequence[] resolved = new CharSequence[size];
 			if (this.resolved != null) {
-				System.arraycopy(this.resolved, 0, resolved, 0, Math.min(size, this.size));
+				System.arraycopy(this.resolved, offset, resolved, 0, Math.min(size, this.size));
 			}
 			return resolved;
 		}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@ package org.springframework.boot.context.properties.source;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 
 import org.junit.jupiter.api.Test;
 
@@ -492,6 +493,21 @@ class ConfigurationPropertyNameTests {
 		assertThat(name.subName(2)).hasToString("baz");
 	}
 
+	@Test
+	void subNameOfAdaptedNameWhenOffsetLessThanSizeShouldReturnSubName() {
+		ConfigurationPropertyName name = ConfigurationPropertyName.adapt("MY_LOGGING_LEVEL_ONE", '_');
+		assertThat(name.subName(1)).hasToString("logging.level.one");
+		assertThat(name.subName(2)).hasToString("level.one");
+	}
+
+	@Test
+	void subNameOfAdaptedNameWithValueProcessorWhenOffsetLessThanSizeShouldReturnSubName() {
+		ConfigurationPropertyName name = ConfigurationPropertyName.adapt("MY_LOGGING_LEVEL_ONE", '_',
+				(value) -> value.toString().toLowerCase(Locale.ENGLISH));
+		assertThat(name.subName(1)).hasToString("logging.level.one");
+		assertThat(name.subName(2)).hasToString("level.one");
+	}
+
 	@Test
 	void subNameWhenOffsetZeroShouldReturnName() {
 		ConfigurationPropertyName name = ConfigurationPropertyName.of("foo.bar.baz");