undefine already defined item + remove mark feature

examples/no_inherit/a/main.fmf

@@ -1,2 +1,6 @@
 /inherited:
   special!: 2
+/stop_inherit:
+  c!: stop
+  /no_c:
+    test: x

examples/no_inherit/main.fmf

@@ -1,5 +1,6 @@
 special!: 1
 x: X
+c: cc
 /a:
   b: b
   x!: abc

fmf/base.py

@@ -58,6 +58,9 @@ def __init__(self, data, name=None, parent=None):
         # (needed to prevent removing nodes with an empty dict).
         self._updated = False
 
+        # stop inheritance item
+        self.stop_inheritance_list = list()
+
         # Store symlinks in while walking tree in grow() to detect
         # symlink loops
         if parent is None:
@@ -218,6 +221,16 @@ def init(path):
                 root, error))
         return root
 
+    def _stop_inherit_item(self, item: str):
+        if item in self.stop_inheritance_list:
+            print(f"{item} already")
+            return item[:-1]
+        elif item.endswith('!'):
+            print(f"{item} ADD")
+            self.stop_inheritance_list.append(item)
+            return item[:-1]
+        return None
+
     def merge(self, parent=None):
         """ Merge parent data """
         # Check parent, append source files
@@ -230,12 +243,12 @@ def merge(self, parent=None):
         # Merge child data with parent da
         for key, value in parent.data.items():
             # avoid to copy data if marked as stop inheritance
-            if not key.endswith('!'):
-                print(f"no inherit {value}")
+            if key + "!" not in parent.stop_inheritance_list:
                 data[key] = copy.deepcopy(value)
-
         self._merge_special(data, self.data)
-        self.data = data
+        for key, value in data.items():
+            item = self._stop_inherit_item(key) or key
+            self.data[item] = data[key]
 
     def inherit(self):
         """ Apply inheritance """
@@ -274,7 +287,8 @@ def update(self, data):
                 self.child(name, value)
             # Update regular attributes
             else:
-                self.data[key] = value
+                item = self._stop_inherit_item(key) or key
+                self.data[item] = data[key]
         log.debug("Data for '{0}' updated.".format(self))
         log.data(pretty(self.data))
 

tests/unit/test_no_inheritance_mark.py

@@ -15,10 +15,18 @@ def setUp(self):
         self.path = EXAMPLES + "no_inherit"
         self.tree = fmf.Tree(self.path)
 
-    def test(self):
+    def test_base(self):
         root_item = self.tree.find('/')
         a_item = self.tree.find('/a')
         inherite_item = self.tree.find('/a/inherited')
-        self.assertIn("special!", root_item.data)
-        self.assertIn("special!", inherite_item.data)
-        self.assertNotIn("special!", a_item.data)
+        self.assertIn("special", root_item.data)
+        self.assertIn("special", inherite_item.data)
+        self.assertNotIn("special", a_item.data)
+
+    def test_undefine(self):
+        c_item = self.tree.find("/a/stop_inherit")
+        no_c_item = self.tree.find("/a/stop_inherit/no_c")
+        self.assertNotIn("special", c_item.data)
+        self.assertNotIn("special", no_c_item.data)
+        self.assertIn("c", c_item.data)
+        self.assertNotIn("c", no_c_item.data)