rule: fmt: support pulling meta from the rule instance

capa/rules.py

@@ -533,11 +533,18 @@ class Rule(object):
         #  - ordering the meta elements
         #  - indenting the nested items with two spaces
         #
+        # updates to the rule will be synced for meta fields,
+        # but not for rule logic.
+        # programmatic generation of rules is not yet supported.
 
         definition = yaml.load(self.definition)
         # definition retains a reference to `meta`,
         # so we're updating that in place.
-        meta = definition["rule"]["meta"]
+        definition["rule"]["meta"] = self.meta
+        meta = self.meta
+
+        meta["name"] = self.name
+        meta["scope"] = self.scope
 
         def move_to_end(m, k):
             # ruamel.yaml uses an ordereddict-like structure to track maps (CommentedMap).

tests/test_fmt.py

@@ -70,3 +70,24 @@ def test_rule_reformat_order():
                - number: 2''')
 
     assert capa.rules.Rule.from_yaml(rule).to_yaml() == EXPECTED
+
+
+def test_rule_reformat_meta_update():
+    rule = textwrap.dedent('''\
+         rule:
+           meta:
+             author: user@domain.com
+             examples:
+               - foo1234
+               - bar5678
+             scope: function
+             name: AAAA
+           features:
+             - and:
+               - number: 1
+               - number: 2''')
+
+    rule = capa.rules.Rule.from_yaml(rule)
+    rule.name = "test rule"
+    assert rule.to_yaml() == EXPECTED
+