StringUtils.cleanPath retains plain pointer to current directory

Issue: SPR-16908

spring-core/src/main/java/org/springframework/util/StringUtils.java

@@ -646,7 +646,7 @@ public abstract class StringUtils {
 		String prefix = "";
 		if (prefixIndex != -1) {
 			prefix = pathToUse.substring(0, prefixIndex + 1);
-			if (prefix.contains("/")) {
+			if (prefix.contains(FOLDER_SEPARATOR)) {
 				prefix = "";
 			}
 			else {
@@ -659,7 +659,7 @@ public abstract class StringUtils {
 		}
 
 		String[] pathArray = delimitedListToStringArray(pathToUse, FOLDER_SEPARATOR);
-		List<String> pathElements = new LinkedList<>();
+		LinkedList<String> pathElements = new LinkedList<>();
 		int tops = 0;
 
 		for (int i = pathArray.length - 1; i >= 0; i--) {
@@ -687,6 +687,10 @@ public abstract class StringUtils {
 		for (int i = 0; i < tops; i++) {
 			pathElements.add(0, TOP_PATH);
 		}
+		// If nothing else left, at least explicitly point to current path.
+		if (pathElements.size() == 1 && "".equals(pathElements.getLast()) && !prefix.endsWith(FOLDER_SEPARATOR)) {
+			pathElements.add(0, CURRENT_PATH);
+		}
 
 		return prefix + collectionToDelimitedString(pathElements, FOLDER_SEPARATOR);
 	}

spring-core/src/test/java/org/springframework/util/StringUtilsTests.java

@@ -378,53 +378,59 @@ public class StringUtilsTests {
 		assertEquals("../mypath/myfile", StringUtils.cleanPath("mypath/../../mypath/myfile"));
 		assertEquals("/../mypath/myfile", StringUtils.cleanPath("/../mypath/myfile"));
 		assertEquals("/mypath/myfile", StringUtils.cleanPath("/a/:b/../../mypath/myfile"));
-		assertEquals("file:///c:/path/to/the%20file.txt", StringUtils.cleanPath("file:///c:/some/../path/to/the%20file.txt"));
+		assertEquals("/", StringUtils.cleanPath("/"));
+		assertEquals("/", StringUtils.cleanPath("/mypath/../"));
+		assertEquals("", StringUtils.cleanPath("mypath/.."));
+		assertEquals("", StringUtils.cleanPath("mypath/../."));
+		assertEquals("./", StringUtils.cleanPath("mypath/../"));
+		assertEquals("./", StringUtils.cleanPath("././"));
+		assertEquals("./", StringUtils.cleanPath("./"));
+		assertEquals("../", StringUtils.cleanPath("../"));
+		assertEquals("../", StringUtils.cleanPath("./../"));
+		assertEquals("../", StringUtils.cleanPath(".././"));
+		assertEquals("file:/", StringUtils.cleanPath("file:/"));
+		assertEquals("file:/", StringUtils.cleanPath("file:/mypath/../"));
+		assertEquals("file:", StringUtils.cleanPath("file:mypath/.."));
+		assertEquals("file:", StringUtils.cleanPath("file:mypath/../."));
+		assertEquals("file:./", StringUtils.cleanPath("file:mypath/../"));
+		assertEquals("file:./", StringUtils.cleanPath("file:././"));
+		assertEquals("file:./", StringUtils.cleanPath("file:./"));
+		assertEquals("file:../", StringUtils.cleanPath("file:../"));
+		assertEquals("file:../", StringUtils.cleanPath("file:./../"));
+		assertEquals("file:../", StringUtils.cleanPath("file:.././"));
+		assertEquals("file:///c:/path/the%20file.txt", StringUtils.cleanPath("file:///c:/some/../path/the%20file.txt"));
 	}
 
 	@Test
 	public void testPathEquals() {
 		assertTrue("Must be true for the same strings",
-				StringUtils.pathEquals("/dummy1/dummy2/dummy3",
-						"/dummy1/dummy2/dummy3"));
+				StringUtils.pathEquals("/dummy1/dummy2/dummy3", "/dummy1/dummy2/dummy3"));
 		assertTrue("Must be true for the same win strings",
-				StringUtils.pathEquals("C:\\dummy1\\dummy2\\dummy3",
-						"C:\\dummy1\\dummy2\\dummy3"));
+				StringUtils.pathEquals("C:\\dummy1\\dummy2\\dummy3", "C:\\dummy1\\dummy2\\dummy3"));
 		assertTrue("Must be true for one top path on 1",
-				StringUtils.pathEquals("/dummy1/bin/../dummy2/dummy3",
-						"/dummy1/dummy2/dummy3"));
+				StringUtils.pathEquals("/dummy1/bin/../dummy2/dummy3", "/dummy1/dummy2/dummy3"));
 		assertTrue("Must be true for one win top path on 2",
-				StringUtils.pathEquals("C:\\dummy1\\dummy2\\dummy3",
-						"C:\\dummy1\\bin\\..\\dummy2\\dummy3"));
+				StringUtils.pathEquals("C:\\dummy1\\dummy2\\dummy3", "C:\\dummy1\\bin\\..\\dummy2\\dummy3"));
 		assertTrue("Must be true for two top paths on 1",
-				StringUtils.pathEquals("/dummy1/bin/../dummy2/bin/../dummy3",
-						"/dummy1/dummy2/dummy3"));
+				StringUtils.pathEquals("/dummy1/bin/../dummy2/bin/../dummy3", "/dummy1/dummy2/dummy3"));
 		assertTrue("Must be true for two win top paths on 2",
-				StringUtils.pathEquals("C:\\dummy1\\dummy2\\dummy3",
-						"C:\\dummy1\\bin\\..\\dummy2\\bin\\..\\dummy3"));
+				StringUtils.pathEquals("C:\\dummy1\\dummy2\\dummy3", "C:\\dummy1\\bin\\..\\dummy2\\bin\\..\\dummy3"));
 		assertTrue("Must be true for double top paths on 1",
-				StringUtils.pathEquals("/dummy1/bin/tmp/../../dummy2/dummy3",
-						"/dummy1/dummy2/dummy3"));
+				StringUtils.pathEquals("/dummy1/bin/tmp/../../dummy2/dummy3", "/dummy1/dummy2/dummy3"));
 		assertTrue("Must be true for double top paths on 2 with similarity",
-				StringUtils.pathEquals("/dummy1/dummy2/dummy3",
-						"/dummy1/dum/dum/../../dummy2/dummy3"));
+				StringUtils.pathEquals("/dummy1/dummy2/dummy3", "/dummy1/dum/dum/../../dummy2/dummy3"));
 		assertTrue("Must be true for current paths",
-				StringUtils.pathEquals("./dummy1/dummy2/dummy3",
-						"dummy1/dum/./dum/../../dummy2/dummy3"));
+				StringUtils.pathEquals("./dummy1/dummy2/dummy3", "dummy1/dum/./dum/../../dummy2/dummy3"));
 		assertFalse("Must be false for relative/absolute paths",
-				StringUtils.pathEquals("./dummy1/dummy2/dummy3",
-						"/dummy1/dum/./dum/../../dummy2/dummy3"));
+				StringUtils.pathEquals("./dummy1/dummy2/dummy3", "/dummy1/dum/./dum/../../dummy2/dummy3"));
 		assertFalse("Must be false for different strings",
-				StringUtils.pathEquals("/dummy1/dummy2/dummy3",
-						"/dummy1/dummy4/dummy3"));
+				StringUtils.pathEquals("/dummy1/dummy2/dummy3", "/dummy1/dummy4/dummy3"));
 		assertFalse("Must be false for one false path on 1",
-				StringUtils.pathEquals("/dummy1/bin/tmp/../dummy2/dummy3",
-						"/dummy1/dummy2/dummy3"));
+				StringUtils.pathEquals("/dummy1/bin/tmp/../dummy2/dummy3", "/dummy1/dummy2/dummy3"));
 		assertFalse("Must be false for one false win top path on 2",
-				StringUtils.pathEquals("C:\\dummy1\\dummy2\\dummy3",
-						"C:\\dummy1\\bin\\tmp\\..\\dummy2\\dummy3"));
+				StringUtils.pathEquals("C:\\dummy1\\dummy2\\dummy3", "C:\\dummy1\\bin\\tmp\\..\\dummy2\\dummy3"));
 		assertFalse("Must be false for top path on 1 + difference",
-				StringUtils.pathEquals("/dummy1/bin/../dummy2/dummy3",
-						"/dummy1/dummy2/dummy4"));
+				StringUtils.pathEquals("/dummy1/bin/../dummy2/dummy3", "/dummy1/dummy2/dummy4"));
 	}
 
 	@Test