Get rid of the Element class

The `Element` class is just used for testing. By using `Element` we are
not testing the actual code. Also, every time we implement a new feature
for the `Feature` class, we need to implement it for `Element` as well.
Replace `Element` by `Integer`.

capa/engine.py

@@ -145,22 +145,6 @@ class Some(Statement):
         return Result(success, self, results)
 
 
-class Element(Statement):
-    '''match if the child is contained in the ctx set.'''
-    def __init__(self, child):
-        super(Element, self).__init__()
-        self.child = child
-
-    def __hash__(self):
-        return hash((self.name, self.child))
-
-    def __eq__(self, other):
-        return self.name == other.name and self.child == other.child
-
-    def evaluate(self, ctx):
-        return Result(self.child in ctx, self, [])
-
-
 class Range(Statement):
     '''match if the child is contained in the ctx set with a count in the given range.'''
     def __init__(self, child, min=None, max=None):

capa/ida/explorer/model.py

@@ -322,7 +322,7 @@ class CapaExplorerDataModel(QtCore.QAbstractItemModel):
                     parent2 = parent
             else:
                 parent2 = CapaExplorerDefaultItem(parent, '%d or more' % result.statement.count)
-        elif not isinstance(result.statement, (capa.features.Feature, capa.engine.Element, capa.engine.Range, capa.engine.Regex)):
+        elif not isinstance(result.statement, (capa.features.Feature, capa.engine.Range, capa.engine.Regex)):
             # when rending a structural node (and/or/not) then we only care about the node name.
             '''
             succs = list(filter(lambda c: bool(c), result.children))

capa/main.py

@@ -350,7 +350,7 @@ def render_result(res, indent=''):
                 print('%soptional:' % indent)
         else:
             print('%s%d or more' % (indent, res.statement.count))
-    elif not isinstance(res.statement, (capa.features.Feature, capa.engine.Element, capa.engine.Range, capa.engine.Regex)):
+    elif not isinstance(res.statement, (capa.features.Feature, capa.engine.Range, capa.engine.Regex)):
         # when rending a structural node (and/or/not),
         #  then we only care about the node name.
         #

capa/rules.py

@@ -24,7 +24,6 @@ BASIC_BLOCK_SCOPE = 'basic block'
 
 SUPPORTED_FEATURES = {
     FILE_SCOPE: set([
-        capa.engine.Element,
         capa.features.MatchedRule,
         capa.features.file.Export,
         capa.features.file.Import,
@@ -33,7 +32,6 @@ SUPPORTED_FEATURES = {
         capa.features.String,
     ]),
     FUNCTION_SCOPE: set([
-        capa.engine.Element,
         capa.features.MatchedRule,
         capa.features.insn.API,
         capa.features.insn.Number,
@@ -56,7 +54,6 @@ SUPPORTED_FEATURES = {
         capa.features.Characteristic('recursive call')
     ]),
     BASIC_BLOCK_SCOPE: set([
-        capa.engine.Element,
         capa.features.MatchedRule,
         capa.features.insn.API,
         capa.features.insn.Number,
@@ -180,8 +177,6 @@ def parse_feature(key):
         return capa.features.insn.Mnemonic
     elif key == 'basic blocks':
         return capa.features.basicblock.BasicBlock
-    elif key == 'element':
-        return Element
     elif key.startswith('characteristic(') and key.endswith(')'):
         characteristic = key[len('characteristic('):-len(')')]
         return lambda v: capa.features.Characteristic(characteristic, v)
@@ -311,9 +306,6 @@ def build_statements(d, scope):
                 if term in ('number', 'offset', 'bytes'):
                     value, symbol = parse_symbol(arg, term)
                     feature = Feature(value, symbol)
-                elif term in ('element'):
-                    arg = parse_int(arg)
-                    feature = Feature(arg)
                 else:
                     # arg is string, like:
                     #

tests/test_engine.py

@@ -3,96 +3,95 @@ import textwrap
 import capa.rules
 import capa.engine
 from capa.engine import *
-import capa.features
+from capa.features import *
+from capa.features.insn import *
 
 
-def test_element():
+def test_number():
-    assert Element(1).evaluate(set([0])) == False
+    assert Number(1).evaluate({Number(0): {1}}) == False
-    assert Element(1).evaluate(set([1])) == True
+    assert Number(1).evaluate({Number(1): {1}}) == True
-    assert Element(1).evaluate(set([None])) == False
+    assert Number(1).evaluate({Number(2): {1, 2}}) == False
-    assert Element(1).evaluate(set([''])) == False
-    assert Element(1).evaluate(set([False])) == False
 
 
 def test_and():
-    assert And(Element(1)).evaluate(set([0])) == False
+    assert And(Number(1)).evaluate({Number(0): {1}}) == False
-    assert And(Element(1)).evaluate(set([1])) == True
+    assert And(Number(1)).evaluate({Number(1): {1}}) == True
-    assert And(Element(1), Element(2)).evaluate(set([0])) == False
+    assert And(Number(1), Number(2)).evaluate({Number(0): {1}}) == False
-    assert And(Element(1), Element(2)).evaluate(set([1])) == False
+    assert And(Number(1), Number(2)).evaluate({Number(1): {1}}) == False
-    assert And(Element(1), Element(2)).evaluate(set([2])) == False
+    assert And(Number(1), Number(2)).evaluate({Number(2): {1}}) == False
-    assert And(Element(1), Element(2)).evaluate(set([1, 2])) == True
+    assert And(Number(1), Number(2)).evaluate({Number(1): {1}, Number(2): {2}}) == True
 
 
 def test_or():
-    assert Or(Element(1)).evaluate(set([0])) == False
+    assert Or(Number(1)).evaluate({Number(0): {1}}) == False
-    assert Or(Element(1)).evaluate(set([1])) == True
+    assert Or(Number(1)).evaluate({Number(1): {1}}) == True
-    assert Or(Element(1), Element(2)).evaluate(set([0])) == False
+    assert Or(Number(1), Number(2)).evaluate({Number(0): {1}}) == False
-    assert Or(Element(1), Element(2)).evaluate(set([1])) == True
+    assert Or(Number(1), Number(2)).evaluate({Number(1): {1}}) == True
-    assert Or(Element(1), Element(2)).evaluate(set([2])) == True
+    assert Or(Number(1), Number(2)).evaluate({Number(2): {1}}) == True
-    assert Or(Element(1), Element(2)).evaluate(set([1, 2])) == True
+    assert Or(Number(1), Number(2)).evaluate({Number(1): {1}, Number(2): {2}}) == True
 
 
 def test_not():
-    assert Not(Element(1)).evaluate(set([0])) == True
+    assert Not(Number(1)).evaluate({Number(0): {1}}) == True
-    assert Not(Element(1)).evaluate(set([1])) == False
+    assert Not(Number(1)).evaluate({Number(1): {1}}) == False
 
 
 def test_some():
-    assert Some(0, Element(1)).evaluate(set([0])) == True
+    assert Some(0, Number(1)).evaluate({Number(0): {1}}) == True
-    assert Some(1, Element(1)).evaluate(set([0])) == False
+    assert Some(1, Number(1)).evaluate({Number(0): {1}}) == False
 
-    assert Some(2, Element(1), Element(2), Element(3)).evaluate(set([0])) == False
+    assert Some(2, Number(1), Number(2), Number(3)).evaluate({Number(0): {1}}) == False
-    assert Some(2, Element(1), Element(2), Element(3)).evaluate(set([0, 1])) == False
+    assert Some(2, Number(1), Number(2), Number(3)).evaluate({Number(0): {1}, Number(1): {1}}) == False
-    assert Some(2, Element(1), Element(2), Element(3)).evaluate(set([0, 1, 2])) == True
+    assert Some(2, Number(1), Number(2), Number(3)).evaluate({Number(0): {1}, Number(1): {1}, Number(2): {1}}) == True
-    assert Some(2, Element(1), Element(2), Element(3)).evaluate(set([0, 1, 2, 3])) == True
+    assert Some(2, Number(1), Number(2), Number(3)).evaluate({Number(0): {1}, Number(1): {1}, Number(2): {1}, Number(3): {1}}) == True
-    assert Some(2, Element(1), Element(2), Element(3)).evaluate(set([0, 1, 2, 3, 4])) == True
+    assert Some(2, Number(1), Number(2), Number(3)).evaluate({Number(0): {1}, Number(1): {1}, Number(2): {1}, Number(3): {1}, Number(4): {1}}) == True
 
 
 def test_complex():
     assert True == Or(
-        And(Element(1), Element(2)),
+        And(Number(1), Number(2)),
-        Or(Element(3),
+        Or(Number(3),
-           Some(2, Element(4), Element(5), Element(6)))
+           Some(2, Number(4), Number(5), Number(6)))
-    ).evaluate(set([5, 6, 7, 8]))
+    ).evaluate({Number(5): {1}, Number(6): {1}, Number(7): {1}, Number(8): {1}})
 
     assert False == Or(
-        And(Element(1), Element(2)),
+        And(Number(1), Number(2)),
-        Or(Element(3),
+        Or(Number(3),
-           Some(2, Element(4), Element(5)))
+           Some(2, Number(4), Number(5)))
-    ).evaluate(set([5, 6, 7, 8]))
+    ).evaluate({Number(5): {1}, Number(6): {1}, Number(7): {1}, Number(8): {1}})
 
 
 def test_range():
     # unbounded range, but no matching feature
-    assert Range(Element(1)).evaluate({Element(2): {}}) == False
+    assert Range(Number(1)).evaluate({Number(2): {}}) == False
 
     # unbounded range with matching feature should always match
-    assert Range(Element(1)).evaluate({Element(1): {}}) == True
+    assert Range(Number(1)).evaluate({Number(1): {}}) == True
-    assert Range(Element(1)).evaluate({Element(1): {0}}) == True
+    assert Range(Number(1)).evaluate({Number(1): {0}}) == True
 
     # unbounded max
-    assert Range(Element(1), min=1).evaluate({Element(1): {0}}) == True
+    assert Range(Number(1), min=1).evaluate({Number(1): {0}}) == True
-    assert Range(Element(1), min=2).evaluate({Element(1): {0}}) == False
+    assert Range(Number(1), min=2).evaluate({Number(1): {0}}) == False
-    assert Range(Element(1), min=2).evaluate({Element(1): {0, 1}}) == True
+    assert Range(Number(1), min=2).evaluate({Number(1): {0, 1}}) == True
 
     # unbounded min
-    assert Range(Element(1), max=0).evaluate({Element(1): {0}}) == False
+    assert Range(Number(1), max=0).evaluate({Number(1): {0}}) == False
-    assert Range(Element(1), max=1).evaluate({Element(1): {0}}) == True
+    assert Range(Number(1), max=1).evaluate({Number(1): {0}}) == True
-    assert Range(Element(1), max=2).evaluate({Element(1): {0}}) == True
+    assert Range(Number(1), max=2).evaluate({Number(1): {0}}) == True
-    assert Range(Element(1), max=2).evaluate({Element(1): {0, 1}}) == True
+    assert Range(Number(1), max=2).evaluate({Number(1): {0, 1}}) == True
-    assert Range(Element(1), max=2).evaluate({Element(1): {0, 1, 3}}) == False
+    assert Range(Number(1), max=2).evaluate({Number(1): {0, 1, 3}}) == False
 
     # we can do an exact match by setting min==max
-    assert Range(Element(1), min=1, max=1).evaluate({Element(1): {}}) == False
+    assert Range(Number(1), min=1, max=1).evaluate({Number(1): {}}) == False
-    assert Range(Element(1), min=1, max=1).evaluate({Element(1): {1}}) == True
+    assert Range(Number(1), min=1, max=1).evaluate({Number(1): {1}}) == True
-    assert Range(Element(1), min=1, max=1).evaluate({Element(1): {1, 2}}) == False
+    assert Range(Number(1), min=1, max=1).evaluate({Number(1): {1, 2}}) == False
 
     # bounded range
-    assert Range(Element(1), min=1, max=3).evaluate({Element(1): {}}) == False
+    assert Range(Number(1), min=1, max=3).evaluate({Number(1): {}}) == False
-    assert Range(Element(1), min=1, max=3).evaluate({Element(1): {1}}) == True
+    assert Range(Number(1), min=1, max=3).evaluate({Number(1): {1}}) == True
-    assert Range(Element(1), min=1, max=3).evaluate({Element(1): {1, 2}}) == True
+    assert Range(Number(1), min=1, max=3).evaluate({Number(1): {1, 2}}) == True
-    assert Range(Element(1), min=1, max=3).evaluate({Element(1): {1, 2, 3}}) == True
+    assert Range(Number(1), min=1, max=3).evaluate({Number(1): {1, 2, 3}}) == True
-    assert Range(Element(1), min=1, max=3).evaluate({Element(1): {1, 2, 3, 4}}) == False
+    assert Range(Number(1), min=1, max=3).evaluate({Number(1): {1, 2, 3, 4}}) == False
 
 
 def test_match_adds_matched_rule_feature():

tests/test_rules.py

@@ -3,14 +3,13 @@ import textwrap
 import pytest
 
 import capa.rules
-from capa.engine import Element
 from capa.features.insn import Number, Offset
 
 
 def test_rule_ctor():
-    r = capa.rules.Rule('test rule', capa.rules.FUNCTION_SCOPE, Element(1), {})
+    r = capa.rules.Rule('test rule', capa.rules.FUNCTION_SCOPE, Number(1), {})
-    assert r.evaluate(set([0])) == False
+    assert r.evaluate({Number(0): {1}}) == False
-    assert r.evaluate(set([1])) == True
+    assert r.evaluate({Number(1): {1}}) == True
 
 
 def test_rule_yaml():
@@ -25,14 +24,14 @@ def test_rule_yaml():
                     - bar5678
             features:
                 - and:
-                    - element: 1
+                    - number: 1
-                    - element: 2
+                    - number: 2
     ''')
     r = capa.rules.Rule.from_yaml(rule)
-    assert r.evaluate(set([0])) == False
+    assert r.evaluate({Number(0): {1}}) == False
-    assert r.evaluate(set([0, 1])) == False
+    assert r.evaluate({Number(0): {1}, Number(1): {1}}) == False
-    assert r.evaluate(set([0, 1, 2])) == True
+    assert r.evaluate({Number(0): {1}, Number(1): {1}, Number(2): {1}}) == True
-    assert r.evaluate(set([0, 1, 2, 3])) == True
+    assert r.evaluate({Number(0): {1}, Number(1): {1}, Number(2): {1}, Number(3): {1}}) == True
 
 
 def test_rule_yaml_complex():
@@ -43,18 +42,18 @@ def test_rule_yaml_complex():
             features:
                 - or:
                     - and:
-                        - element: 1
+                        - number: 1
-                        - element: 2
+                        - number: 2
                     - or:
-                        - element: 3
+                        - number: 3
                         - 2 or more:
-                            - element: 4
+                            - number: 4
-                            - element: 5
+                            - number: 5
-                            - element: 6
+                            - number: 6
     ''')
     r = capa.rules.Rule.from_yaml(rule)
-    assert r.evaluate(set([5, 6, 7, 8])) == True
+    assert r.evaluate({Number(5): {1}, Number(6): {1}, Number(7): {1}, Number(8): {1}}) == True
-    assert r.evaluate(set([6, 7, 8])) == False
+    assert r.evaluate({Number(6): {1}, Number(7): {1}, Number(8): {1}}) == False
 
 
 def test_rule_yaml_not():
@@ -64,13 +63,13 @@ def test_rule_yaml_not():
                     name: test rule
                 features:
                     - and:
-                        - element: 1
+                        - number: 1
                         - not:
-                            - element: 2
+                            - number: 2
         ''')
     r = capa.rules.Rule.from_yaml(rule)
-    assert r.evaluate(set([1])) == True
+    assert r.evaluate({Number(1): {1}}) == True
-    assert r.evaluate(set([1, 2])) == False
+    assert r.evaluate({Number(1): {1}, Number(2): {1}}) == False
 
 
 def test_rule_yaml_count():
@@ -79,12 +78,12 @@ def test_rule_yaml_count():
             meta:
                 name: test rule
             features:
-                - count(element(100)): 1
+                - count(number(100)): 1
     ''')
     r = capa.rules.Rule.from_yaml(rule)
-    assert r.evaluate({Element(100): {}}) == False
+    assert r.evaluate({Number(100): {}}) == False
-    assert r.evaluate({Element(100): {1}}) == True
+    assert r.evaluate({Number(100): {1}}) == True
-    assert r.evaluate({Element(100): {1, 2}}) == False
+    assert r.evaluate({Number(100): {1, 2}}) == False
 
 
 def test_rule_yaml_count_range():
@@ -93,13 +92,13 @@ def test_rule_yaml_count_range():
             meta:
                 name: test rule
             features:
-                - count(element(100)): (1, 2)
+                - count(number(100)): (1, 2)
     ''')
     r = capa.rules.Rule.from_yaml(rule)
-    assert r.evaluate({Element(100): {}}) == False
+    assert r.evaluate({Number(100): {}}) == False
-    assert r.evaluate({Element(100): {1}}) == True
+    assert r.evaluate({Number(100): {1}}) == True
-    assert r.evaluate({Element(100): {1, 2}}) == True
+    assert r.evaluate({Number(100): {1, 2}}) == True
-    assert r.evaluate({Element(100): {1, 2, 3}}) == False
+    assert r.evaluate({Number(100): {1, 2, 3}}) == False
 
 
 def test_invalid_rule_feature():
@@ -239,7 +238,7 @@ def test_invalid_rules():
                     meta:
                         name: test rule
                     features:
-                        - characteristic(count(element(100))): True
+                        - characteristic(count(number(100))): True
             '''))