Create a WildcardMatcher.NONE when creating a WildcardMatcher with an empty string

CHANGELOG.md

@@ -11,6 +11,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Enhancements
 
 ### Bug Fixes
+- Create a WildcardMatcher.NONE when creating a WildcardMatcher with an empty string ([#5694](https://github.com/opensearch-project/security/pull/5694))
 
 ### Refactoring
 

src/main/java/org/opensearch/security/support/WildcardMatcher.java

@@ -162,7 +162,7 @@ public String toString() {
     };
 
     public static WildcardMatcher from(String pattern) {
-        if (pattern == null) {
+        if (pattern == null || pattern.isBlank()) {
             return NONE;
         } else if (pattern.equals("*")) {
             return ANY;

src/test/java/org/opensearch/security/UtilTests.java

@@ -77,6 +77,9 @@ public void testWildcardMatcherClasses() {
         assertTrue(wc("abc").test("abc"));
         assertFalse(wc("ABC").test("abc"));
         assertFalse(wc(null).test("abc"));
+        assertFalse(wc("").test("abc"));
+        // Creating a WildcardMatcher with blank should create a matcher that matches nothing
+        assertFalse(wc("").test(""));
         assertTrue(WildcardMatcher.from(null, "abc").test("abc"));
     }