schema: add state method for conditional if-features

Accessing feature states is useful to enable/disable leafs.
However, when a if-feature contain a condition (not/or/and keywords),
there is currently no way to get the state resulting of the expression.

Add a state method to all IfFeatureExpr objects so a state of the
entire if-feature expression can be evaluated.

Test all basic cases (one operator).

Author: Adrien Vasseur

libyang/schema.py

@@ -793,6 +793,9 @@ def __init__(self, context: "libyang.Context", cdata):
     def feature(self) -> Feature:
         return Feature(self.context, self.cdata)
 
+    def state(self) -> bool:
+        return self.feature().state()
+
     def dump(self, indent: int = 0) -> str:
         feat = self.feature()
         return "%s%s [%s]\n" % (" " * indent, feat.name(), feat.description())
@@ -810,6 +813,9 @@ def __init__(self, context: "libyang.Context", child: IfFeatureExprTree):
         self.context = context
         self.child = child
 
+    def state(self) -> bool:
+        return not self.child.state()
+
     def dump(self, indent: int = 0) -> str:
         return " " * indent + "NOT\n" + self.child.dump(indent + 1)
 
@@ -829,6 +835,9 @@ def __init__(
         self.a = a
         self.b = b
 
+    def state(self) -> bool:
+        return self.a.state() and self.b.state()
+
     def dump(self, indent: int = 0) -> str:
         s = " " * indent + "AND\n"
         s += self.a.dump(indent + 1)
@@ -851,6 +860,9 @@ def __init__(
         self.a = a
         self.b = b
 
+    def state(self) -> bool:
+        return self.a.state() or self.b.state()
+
     def dump(self, indent: int = 0) -> str:
         s = " " * indent + "OR\n"
         s += self.a.dump(indent + 1)

tests/test_diff.py

@@ -38,6 +38,8 @@ class DiffTest(unittest.TestCase):
             (NodeTypeAdded, "/yolo-system:state/number"),
             (NodeTypeRemoved, "/yolo-system:conf/number"),
             (NodeTypeRemoved, "/yolo-system:state/number"),
+            (SNodeAdded, "/yolo-system:conf/full"),
+            (SNodeAdded, "/yolo-system:state/full"),
             (SNodeAdded, "/yolo-system:conf/hostname-ref"),
             (SNodeAdded, "/yolo-system:conf/url/enabled"),
             (SNodeAdded, "/yolo-system:conf/url/fetch"),

tests/test_schema.py

@@ -135,8 +135,8 @@ def test_rev_extensions(self):
 class IfFeatureTest(unittest.TestCase):
     def setUp(self):
         self.ctx = Context(YANG_DIR)
-        mod = self.ctx.load_module("yolo-system")
-        mod.feature_enable_all()
+        self.mod = self.ctx.load_module("yolo-system")
+        self.mod.feature_enable_all()
         self.leaf = next(
             self.ctx.find_path("/yolo-system:conf/yolo-system:isolation-level")
         )
@@ -158,6 +158,61 @@ def test_iffeature_tree(self):
         self.assertEqual(tree.a.feature().name(), "turbo-boost")
         self.assertEqual(tree.b.feature().name(), "networking")
 
+    def test_iffeature_state(self):
+        def feature_disable_only(feature):
+            self.mod.feature_disable_all()
+            for f in self.mod.features():
+                if f.name() == feature:
+                    continue
+                self.mod.feature_enable(f.name())
+
+        leaf_simple = next(self.ctx.find_path("/yolo-system:conf/yolo-system:speed"))
+
+        self.mod.feature_disable_all()
+        leaf_not = next(self.ctx.find_path("/yolo-system:conf/yolo-system:offline"))
+        self.mod.feature_enable_all()
+
+        leaf_and = next(self.ctx.find_path("/yolo-system:conf/yolo-system:full"))
+        leaf_or = next(
+            self.ctx.find_path("/yolo-system:conf/yolo-system:isolation-level")
+        )
+
+        # if-feature is just a feature
+        tree = next(leaf_simple.if_features()).tree()
+        self.mod.feature_enable_all()
+        self.assertEqual(tree.state(), True)
+        self.mod.feature_disable_all()
+        self.assertEqual(tree.state(), False)
+
+        # if-feature is "NOT networking"
+        tree = next(leaf_not.if_features()).tree()
+        self.mod.feature_enable_all()
+        self.assertEqual(tree.state(), False)
+        self.mod.feature_disable_all()
+        self.assertEqual(tree.state(), True)
+
+        # if-feature is "turbo-boost AND networking"
+        tree = next(leaf_and.if_features()).tree()
+        self.mod.feature_enable_all()
+        self.assertEqual(tree.state(), True)
+        self.mod.feature_disable_all()
+        self.assertEqual(tree.state(), False)
+        feature_disable_only("turbo-boost")
+        self.assertEqual(tree.state(), False)
+        feature_disable_only("networking")
+        self.assertEqual(tree.state(), False)
+
+        # if-feature is "turbo-boost OR networking"
+        tree = next(leaf_or.if_features()).tree()
+        self.mod.feature_enable_all()
+        self.assertEqual(tree.state(), True)
+        self.mod.feature_disable_all()
+        self.assertEqual(tree.state(), False)
+        feature_disable_only("turbo-boost")
+        self.assertEqual(tree.state(), True)
+        feature_disable_only("networking")
+        self.assertEqual(tree.state(), True)
+
     def test_iffeature_str(self):
         iff = next(self.leaf.if_features())
         self.assertEqual(str(iff), "turbo-boost OR networking")
@@ -203,11 +258,11 @@ def test_cont_attrs(self):
 
     def test_cont_iter(self):
         children = list(iter(self.container))
-        self.assertEqual(len(children), 8)
+        self.assertEqual(len(children), 9)
 
     def test_cont_children_leafs(self):
         leafs = list(self.container.children(types=(SNode.LEAF,)))
-        self.assertEqual(len(leafs), 6)
+        self.assertEqual(len(leafs), 7)
 
     def test_cont_parent(self):
         self.assertIsNone(self.container.parent())

tests/yang/yolo/yolo-system.yang

@@ -106,6 +106,20 @@ module yolo-system {
       type uint32;
     }
 
+    leaf offline {
+      description
+        "When networking is disabled.";
+      if-feature "not networking";
+      type uint32;
+    }
+
+    leaf full {
+      description
+        "Fast and online.";
+      if-feature "turbo-boost and networking";
+      type uint32;
+    }
+
     leaf isolation-level {
       description
         "The level of isolation.";