Fix #788 (JsonPointer.empty() should not match any index or property)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -45,6 +45,8 @@ JSON library.
 #774: Add a feature to allow leading plus sign
   (`JsonReadFeature.ALLOW_LEADING_PLUS_SIGN_FOR_NUMBERS`)
  (contributed by @pjfanning)
+#788: `JsonPointer.empty()` should NOT indicate match of a property
+  with key of ""
 
 2.13.3 (14-May-2022)
 

src/main/java/com/fasterxml/jackson/core/JsonPointer.java

@@ -84,7 +84,8 @@ public class JsonPointer implements Serializable
      */
     protected JsonPointer() {
         _nextSegment = null;
-        _matchingPropertyName = "";
+        // [core#788]: must be `null` to distinguish from Property with "" as key
+        _matchingPropertyName = null;
         _matchingElementIndex = -1;
         _asString = "";
     }

src/test/java/com/fasterxml/jackson/core/TestJsonPointer.java

@@ -38,7 +38,7 @@ public void testSimplePath() throws Exception
         assertTrue(ptr.matches());
         assertNull(ptr.tail());
         assertNull(ptr.head());
-        assertEquals("", ptr.getMatchingProperty());
+        assertNull(ptr.getMatchingProperty());
         assertEquals(-1, ptr.getMatchingIndex());
     }
 
@@ -80,21 +80,37 @@ public void testLast()
         assertEquals("name", leaf.getMatchingProperty());
     }
 
-    public void testEmpty()
+    public void testEmptyPointer()
     {
         assertSame(JsonPointer.EMPTY, JsonPointer.empty());
         assertSame(JsonPointer.EMPTY, JsonPointer.compile(""));
+        final JsonPointer empty = JsonPointer.empty();
+        assertEquals("", empty.toString());
+
+        // As per [core#788], should NOT match Property with "empty String"
+        assertFalse(empty.mayMatchProperty());
+        assertFalse(empty.mayMatchElement());
+        assertEquals(-1, empty.getMatchingIndex());
+        assertNull(empty.getMatchingProperty());
     }
 
-    public void testEmptyName()
+    public void testPointerWithEmptyPropertyName()
     {
         // note: this is acceptable, to match property in '{"":3}', for example
         // and NOT same as what empty point, "", is.
         JsonPointer ptr = JsonPointer.compile("/");
         assertNotNull(ptr);
         assertNotSame(JsonPointer.EMPTY, ptr);
-        
+
         assertEquals("/", ptr.toString());
+        assertTrue(ptr.mayMatchProperty());
+        assertFalse(ptr.mayMatchElement());
+        assertEquals(-1, ptr.getMatchingIndex());
+        assertEquals("", ptr.getMatchingProperty());
+        assertTrue(ptr.matchesProperty(""));
+        assertFalse(ptr.matchesElement(0));
+        assertFalse(ptr.matchesElement(-1));
+        assertFalse(ptr.matchesProperty("1"));
     }
 
     // mostly for test coverage, really...