add tests and fix introduced bug

stix2/pattern_visitor.py

@@ -259,7 +259,7 @@ class STIXPatternVisitorForSTIX2():
             if isinstance(next, TerminalNode):
                 property_path.append(self.instantiate("ListObjectPathComponent", current.property_name, next.getText()))
                 i += 2
-            if isinstance(next, IntegerConstant):
+            elif isinstance(next, IntegerConstant):
                 property_path.append(self.instantiate("ListObjectPathComponent", current.property_name, next.value))
                 i += 2
             else:

stix2/test/v20/test_pattern_expressions.py

@@ -512,15 +512,20 @@ def test_parsing_start_stop_qualified_expression():
 
 
 def test_parsing_mixed_boolean_expression_1():
-    patt_obj = create_pattern_object("[a:b = 1 AND a:b = 2 OR a:b = 3]",)
+    patt_obj = create_pattern_object("[a:b = 1 AND a:b = 2 OR a:b = 3]")
     assert str(patt_obj) == "[a:b = 1 AND a:b = 2 OR a:b = 3]"
 
 
 def test_parsing_mixed_boolean_expression_2():
-    patt_obj = create_pattern_object("[a:b = 1 OR a:b = 2 AND a:b = 3]",)
+    patt_obj = create_pattern_object("[a:b = 1 OR a:b = 2 AND a:b = 3]")
     assert str(patt_obj) == "[a:b = 1 OR a:b = 2 AND a:b = 3]"
 
 
+def test_parsing_integer_index():
+    patt_obj = create_pattern_object("[a:b[1]=2]")
+    assert str(patt_obj) == "[a:b[1] = 2]"
+
+
 def test_parsing_illegal_start_stop_qualified_expression():
     with pytest.raises(ValueError):
         create_pattern_object("[ipv4-addr:value = '1.2.3.4'] START '2016-06-01' STOP '2017-03-12T08:30:00Z'", version="2.0")

stix2/test/v21/test_pattern_expressions.py

@@ -654,6 +654,11 @@ def test_parsing_mixed_boolean_expression_2():
     assert str(patt_obj) == "[a:b = 1 OR a:b = 2 AND a:b = 3]"
 
 
+def test_parsing_integer_index():
+    patt_obj = create_pattern_object("[a:b[1]=2]")
+    assert str(patt_obj) == "[a:b[1] = 2]"
+
+
 def test_parsing_multiple_slashes_quotes():
     patt_obj = create_pattern_object("[ file:name = 'weird_name\\'' ]", version="2.1")
     assert str(patt_obj) == "[file:name = 'weird_name\\'']"