Support symlinks in configtree property paths

Prior to this commit, the configtree property source would not traverse
into a sub-directory in a property path if the sub-directory was a
symbolic link. This commit allows symlinked sub-directories to be
traversed like any other sub-directory in the property path.

Fixes gh-24530

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/ConfigTreePropertySource.java

@@ -19,6 +19,7 @@
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.file.FileVisitOption;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.attribute.BasicFileAttributes;
@@ -203,15 +204,16 @@ Origin getOrigin() {
 		static Map<String, PropertyFile> findAll(Path sourceDirectory, Set<Option> options) {
 			try {
 				Map<String, PropertyFile> propertyFiles = new TreeMap<>();
-				Files.find(sourceDirectory, MAX_DEPTH, PropertyFile::isPropertyFile).forEach((path) -> {
-					String name = getName(sourceDirectory.relativize(path));
-					if (StringUtils.hasText(name)) {
-						if (options.contains(Option.USE_LOWERCASE_NAMES)) {
-							name = name.toLowerCase();
-						}
-						propertyFiles.put(name, new PropertyFile(path, options));
-					}
-				});
+				Files.find(sourceDirectory, MAX_DEPTH, PropertyFile::isPropertyFile, FileVisitOption.FOLLOW_LINKS)
+						.forEach((path) -> {
+							String name = getName(sourceDirectory.relativize(path));
+							if (StringUtils.hasText(name)) {
+								if (options.contains(Option.USE_LOWERCASE_NAMES)) {
+									name = name.toLowerCase();
+								}
+								propertyFiles.put(name, new PropertyFile(path, options));
+							}
+						});
 				return Collections.unmodifiableMap(propertyFiles);
 			}
 			catch (IOException ex) {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/env/ConfigTreePropertySourceTests.java

@@ -88,6 +88,15 @@ void getPropertyNamesFromNestedReturnsPropertyNames() throws Exception {
 		assertThat(propertySource.getPropertyNames()).containsExactly("c", "fa.a", "fa.b", "fb.a", "fb.fa.a");
 	}
 
+	@Test
+	void getPropertyNamesFromNestedWithSymlinkInPathReturnsPropertyNames() throws Exception {
+		addNested();
+		Path symlinkTempDir = Files.createSymbolicLink(this.directory.resolveSibling("symlinkTempDir"), this.directory);
+		ConfigTreePropertySource propertySource = new ConfigTreePropertySource("test", symlinkTempDir);
+		Files.delete(symlinkTempDir);
+		assertThat(propertySource.getPropertyNames()).containsExactly("c", "fa.a", "fa.b", "fb.a", "fb.fa.a");
+	}
+
 	@Test
 	void getPropertyNamesFromFlatWithSymlinksIgnoresHiddenFiles() throws Exception {
 		ConfigTreePropertySource propertySource = getSymlinkedFlatPropertySource();