Fix array index validation to reject indices with leading zeros

Co-authored-by: stefankoegl <[email protected]>

Author: Copilot

jsonpointer.py

@@ -152,7 +152,7 @@ class JsonPointer(object):
 
     # Array indices must not contain:
     # leading zeros, signs, spaces, decimals, etc
-    _RE_ARRAY_INDEX = re.compile('0|[1-9][0-9]*$')
+    _RE_ARRAY_INDEX = re.compile('^(?:0|[1-9][0-9]*)$')
     _RE_INVALID_ESCAPE = re.compile('(~[^01]|~$)')
 
     def __init__(self, pointer):

tests.py

@@ -219,6 +219,13 @@ def test_invalid_index(self):
         # 'a' is not a valid list index
         doc = [0, 1, 2]
         self.assertRaises(JsonPointerException, resolve_pointer, doc, '/a')
+        
+    def test_invalid_index_leading_zeros(self):
+        # RFC 6901 specifies that array indices must not have leading zeros
+        doc = [0, 1, 2]
+        self.assertRaises(JsonPointerException, resolve_pointer, doc, '/01')
+        self.assertRaises(JsonPointerException, resolve_pointer, doc, '/00')
+        self.assertRaises(JsonPointerException, resolve_pointer, doc, '/001')
 
     def test_oob(self):
         # this list does not have 10 members