Complete the addition of AST node class override support which

was begun by frank7y.  Added some unit tests.

Also address a design flaw which prevented the AST builder
function create_pattern_object() from honoring module_suffix
and module_name parameters after the first call.

stix2/pattern_visitor.py

@@ -53,22 +53,32 @@ def same_boolean_operator(current_op, op_token):
 
 
 class STIXPatternVisitorForSTIX2():
-    classes = {}
+
+    def __init__(self, parser_class, module_suffix=None, module_name=None):
+        self.parser_class = parser_class
+
+        if module_suffix and module_name:
+            self.module_suffix = module_suffix
+            self.module = importlib.import_module(module_name)
+        else:
+            self.module_suffix = self.module = None
 
     def get_class(self, class_name):
-        if class_name in STIXPatternVisitorForSTIX2.classes:
+        klass = None
-            return STIXPatternVisitorForSTIX2.classes[class_name]
+        if self.module:
-        else:
+            class_name_suffix = class_name + "For" + self.module_suffix
-            return None
+            member = getattr(self.module, class_name_suffix, None)
+            if member and inspect.isclass(member):
+                klass = member
 
-    def instantiate(self, klass_name, *args):
+        if not klass:
-        klass_to_instantiate = None
+            klass = globals()[class_name]
-        if self.module_suffix:
+
-            klass_to_instantiate = self.get_class(klass_name + "For" + self.module_suffix)
+        return klass
-        if not klass_to_instantiate:
+
-            # use the classes in python_stix2
+    def instantiate(self, klass_name, *args, **kwargs):
-            klass_to_instantiate = globals()[klass_name]
+        klass_to_instantiate = self.get_class(klass_name)
-        return klass_to_instantiate(*args)
+        return klass_to_instantiate(*args, **kwargs)
 
     # Visit a parse tree produced by STIXPatternParser#pattern.
     def visitPattern(self, ctx):
@@ -330,12 +340,12 @@ class STIXPatternVisitorForSTIX2():
         elif node.symbol.type == self.parser_class.FloatPosLiteral or node.symbol.type == self.parser_class.FloatNegLiteral:
             return self.instantiate("FloatConstant", node.getText())
         elif node.symbol.type == self.parser_class.HexLiteral:
-            return HexConstant(node.getText(), from_parse_tree=True)
+            return self.instantiate("HexConstant", node.getText(), from_parse_tree=True)
         elif node.symbol.type == self.parser_class.BinaryLiteral:
-            return BinaryConstant(node.getText(), from_parse_tree=True)
+            return self.instantiate("BinaryConstant", node.getText(), from_parse_tree=True)
         elif node.symbol.type == self.parser_class.StringLiteral:
             if node.getText()[0] == "'" and node.getText()[-1] == "'":
-                return StringConstant(node.getText()[1:-1], from_parse_tree=True)
+                return self.instantiate("StringConstant", node.getText()[1:-1], from_parse_tree=True)
             else:
                 raise ParseException("The pattern does not start and end with a single quote")
         elif node.symbol.type == self.parser_class.BoolLiteral:
@@ -356,37 +366,14 @@ class STIXPatternVisitorForSTIX2():
             aggregate = [nextResult]
         return aggregate
 
+
 # This class defines a complete generic visitor for a parse tree produced by STIXPatternParser.
 class STIXPatternVisitorForSTIX21(STIXPatternVisitorForSTIX2, STIXPatternVisitor21):
-    classes = {}
+    pass
-
-    def __init__(self, module_suffix, module_name):
-        if module_suffix and module_name:
-            self.module_suffix = module_suffix
-            if not STIXPatternVisitorForSTIX2.classes:
-                module = importlib.import_module(module_name)
-                for k, c in inspect.getmembers(module, inspect.isclass):
-                    STIXPatternVisitorForSTIX2.classes[k] = c
-        else:
-            self.module_suffix = None
-        self.parser_class = STIXPatternParser21
-        super(STIXPatternVisitor21, self).__init__()
 
 
 class STIXPatternVisitorForSTIX20(STIXPatternVisitorForSTIX2, STIXPatternVisitor20):
-    classes = {}
+    pass
-
-    def __init__(self, module_suffix, module_name):
-        if module_suffix and module_name:
-            self.module_suffix = module_suffix
-            if not STIXPatternVisitorForSTIX2.classes:
-                module = importlib.import_module(module_name)
-                for k, c in inspect.getmembers(module, inspect.isclass):
-                    STIXPatternVisitorForSTIX2.classes[k] = c
-        else:
-            self.module_suffix = None
-        self.parser_class = STIXPatternParser20
-        super(STIXPatternVisitor20, self).__init__()
 
 
 def create_pattern_object(pattern, module_suffix="", module_name="", version=DEFAULT_VERSION):
@@ -397,10 +384,14 @@ def create_pattern_object(pattern, module_suffix="", module_name="", version=DEF
     if version == "2.1":
         pattern_class = Pattern21
         visitor_class = STIXPatternVisitorForSTIX21
+        parser_class = STIXPatternParser21
     else:
         pattern_class = Pattern20
         visitor_class = STIXPatternVisitorForSTIX20
+        parser_class = STIXPatternParser20
 
     pattern_obj = pattern_class(pattern)
-    builder = visitor_class(module_suffix, module_name)
+    builder = visitor_class(
+        parser_class, module_suffix, module_name
+    )
     return pattern_obj.visit(builder)

stix2/test/v20/pattern_ast_overrides.py

@@ -0,0 +1,21 @@
+"""
+AST node class overrides for testing the pattern AST builder.
+"""
+from stix2.patterns import (
+    EqualityComparisonExpression,
+    StartStopQualifier,
+    StringConstant
+)
+
+
+class EqualityComparisonExpressionForTesting(EqualityComparisonExpression):
+    pass
+
+
+class StringConstantForTesting(StringConstant):
+    pass
+
+
+class StartStopQualifierForTesting(StartStopQualifier):
+    pass
+

stix2/test/v20/test_pattern_expressions.py

@@ -6,6 +6,8 @@ import pytz
 import stix2
 from stix2.pattern_visitor import create_pattern_object
 import stix2.utils
+import stix2.patterns
+from .pattern_ast_overrides import *
 
 
 def test_create_comparison_expression():
@@ -587,3 +589,58 @@ def test_parsing_illegal_start_stop_qualified_expression():
 def test_list_constant():
     patt_obj = create_pattern_object("[network-traffic:src_ref.value IN ('10.0.0.0', '10.0.0.1', '10.0.0.2')]", version="2.0")
     assert str(patt_obj) == "[network-traffic:src_ref.value IN ('10.0.0.0', '10.0.0.1', '10.0.0.2')]"
+
+
+def test_ast_class_override_comp_equals():
+    patt_ast = create_pattern_object(
+        "[a:b=1]", "Testing", "stix2.test.v20.pattern_ast_overrides",
+        version="2.0"
+    )
+
+    assert isinstance(patt_ast, stix2.patterns.ObservationExpression)
+    assert isinstance(patt_ast.operand, EqualityComparisonExpressionForTesting)
+    assert str(patt_ast) == "[a:b = 1]"
+
+
+def test_ast_class_override_string_constant():
+    patt_ast = create_pattern_object(
+        "[a:'b'[1].'c' < 'foo']", "Testing",
+        "stix2.test.v20.pattern_ast_overrides",
+        version="2.0"
+    )
+
+    assert isinstance(patt_ast, stix2.patterns.ObservationExpression)
+    assert isinstance(
+        patt_ast.operand, stix2.patterns.LessThanComparisonExpression
+    )
+    assert isinstance(
+        patt_ast.operand.lhs.property_path[0].property_name,
+        str
+    )
+    assert isinstance(
+        patt_ast.operand.lhs.property_path[1].property_name,
+        str
+    )
+    assert isinstance(patt_ast.operand.rhs, StringConstantForTesting)
+
+    assert str(patt_ast) == "[a:'b'[1].c < 'foo']"
+
+
+def test_ast_class_override_startstop_qualifier():
+    patt_ast = create_pattern_object(
+        "[a:b=1] START '1993-01-20T01:33:52.592Z' STOP '2001-08-19T23:50:23.129Z'",
+        "Testing", "stix2.test.v20.pattern_ast_overrides", version="2.0"
+    )
+
+    assert isinstance(patt_ast, stix2.patterns.QualifiedObservationExpression)
+    assert isinstance(
+        patt_ast.observation_expression, stix2.patterns.ObservationExpression
+    )
+    assert isinstance(
+        patt_ast.observation_expression.operand,
+        EqualityComparisonExpressionForTesting
+    )
+    assert isinstance(
+        patt_ast.qualifier, StartStopQualifierForTesting
+    )
+    assert str(patt_ast) == "[a:b = 1] START '1993-01-20T01:33:52.592Z' STOP '2001-08-19T23:50:23.129Z'"

stix2/test/v21/pattern_ast_overrides.py

@@ -0,0 +1,21 @@
+"""
+AST node class overrides for testing the pattern AST builder.
+"""
+from stix2.patterns import (
+    EqualityComparisonExpression,
+    StartStopQualifier,
+    StringConstant
+)
+
+
+class EqualityComparisonExpressionForTesting(EqualityComparisonExpression):
+    pass
+
+
+class StringConstantForTesting(StringConstant):
+    pass
+
+
+class StartStopQualifierForTesting(StartStopQualifier):
+    pass
+

stix2/test/v21/test_pattern_expressions.py

@@ -7,6 +7,8 @@ from stix2patterns.exceptions import ParseException
 import stix2
 from stix2.pattern_visitor import create_pattern_object
 import stix2.utils
+import stix2.patterns
+from .pattern_ast_overrides import *
 
 
 def test_create_comparison_expression():
@@ -747,3 +749,58 @@ def test_parsing_multiple_slashes_quotes():
 def test_parse_error():
     with pytest.raises(ParseException):
         create_pattern_object("[ file: name = 'weirdname]", version="2.1")
+
+
+def test_ast_class_override_comp_equals():
+    patt_ast = create_pattern_object(
+        "[a:b=1]", "Testing", "stix2.test.v21.pattern_ast_overrides",
+        version="2.1"
+    )
+
+    assert isinstance(patt_ast, stix2.patterns.ObservationExpression)
+    assert isinstance(patt_ast.operand, EqualityComparisonExpressionForTesting)
+    assert str(patt_ast) == "[a:b = 1]"
+
+
+def test_ast_class_override_string_constant():
+    patt_ast = create_pattern_object(
+        "[a:'b'[1].'c' < 'foo']", "Testing",
+        "stix2.test.v21.pattern_ast_overrides",
+        version="2.1"
+    )
+
+    assert isinstance(patt_ast, stix2.patterns.ObservationExpression)
+    assert isinstance(
+        patt_ast.operand, stix2.patterns.LessThanComparisonExpression
+    )
+    assert isinstance(
+        patt_ast.operand.lhs.property_path[0].property_name,
+        str
+    )
+    assert isinstance(
+        patt_ast.operand.lhs.property_path[1].property_name,
+        str
+    )
+    assert isinstance(patt_ast.operand.rhs, StringConstantForTesting)
+
+    assert str(patt_ast) == "[a:'b'[1].c < 'foo']"
+
+
+def test_ast_class_override_startstop_qualifier():
+    patt_ast = create_pattern_object(
+        "[a:b=1] START t'1993-01-20T01:33:52.592Z' STOP t'2001-08-19T23:50:23.129Z'",
+        "Testing", "stix2.test.v21.pattern_ast_overrides", version="2.1"
+    )
+
+    assert isinstance(patt_ast, stix2.patterns.QualifiedObservationExpression)
+    assert isinstance(
+        patt_ast.observation_expression, stix2.patterns.ObservationExpression
+    )
+    assert isinstance(
+        patt_ast.observation_expression.operand,
+        EqualityComparisonExpressionForTesting
+    )
+    assert isinstance(
+        patt_ast.qualifier, StartStopQualifierForTesting
+    )
+    assert str(patt_ast) == "[a:b = 1] START t'1993-01-20T01:33:52.592Z' STOP t'2001-08-19T23:50:23.129Z'"