Fix PathPattern incorrectly matching variable against root path

Issue: SPR-15264

spring-web/src/main/java/org/springframework/web/util/patterns/CaptureVariablePathElement.java

@@ -80,7 +80,8 @@ class CaptureVariablePathElement extends PathElement {
 		}
 		boolean match = false;
 		if (next == null) {
-			match = (nextPos == matchingContext.candidateLength);
+			// Needs to be at least one character #SPR15264
+			match = (nextPos == matchingContext.candidateLength && nextPos > candidateIndex);
 		}
 		else {
 			if (matchingContext.isMatchStartMatching && nextPos == matchingContext.candidateLength) {

spring-web/src/test/java/org/springframework/web/util/patterns/PathPatternMatcherTests.java

@@ -507,6 +507,31 @@ public class PathPatternMatcherTests {
 		checkExtractPathWithinPattern("/", "//", "");
 	}
 
+	@Test
+	public void extractUriTemplateVariables_spr15264() {
+		PathPattern pp = new PathPatternParser().parse("/{foo}");
+		assertTrue(pp.matches("/abc"));
+		assertFalse(pp.matches("/"));
+		assertFalse(pp.matches("//"));
+		checkCapture("/{foo}", "/abc", "foo", "abc");
+		
+		pp = new PathPatternParser().parse("/{foo}/{bar}");
+		assertTrue(pp.matches("/abc/def"));
+		assertFalse(pp.matches("//def"));
+		assertFalse(pp.matches("//"));
+		
+		pp = parse("/{foo}/boo");
+		assertTrue(pp.matches("/abc/boo"));
+		assertTrue(pp.matches("/a/boo"));
+		assertFalse(pp.matches("//boo"));
+
+		checkCapture("/{word:[a-z]*}", "/abc", "word", "abc");
+		pp = parse("/{word:[a-z]*}");
+		assertFalse(pp.matches("/1"));
+		assertTrue(pp.matches("/a"));
+		assertFalse(pp.matches("/"));
+	}
+	
 	@Test
 	public void extractUriTemplateVariables() throws Exception {
 		checkCapture("/hotels/{hotel}", "/hotels/1", "hotel", "1");