schema: add default function to SChoice class

This patches introduces a default function to SChoice class,
including unit test.

Fixes: #97
Signed-off-by: Stefan Gula <steweg@gmail.com>
Acked-by: Samuel Gauthier <samuel.gauthier@6wind.com>

Author: steweg

cffi/cdefs.h

@@ -1023,6 +1023,19 @@ struct lysc_when {
 
 struct lysc_when** lysc_node_when(const struct lysc_node *);
 
+struct lysc_node_case {
+    struct lysc_node *child;
+    struct lysc_when **when;
+    ...;
+};
+
+struct lysc_node_choice {
+    struct lysc_node_case *cases;
+    struct lysc_when **when;
+    struct lysc_node_case *dflt;
+    ...;
+};
+
 #define LYD_DEFAULT ...
 #define LYD_WHEN_TRUE ...
 #define LYD_NEW ...

libyang/__init__.py

@@ -78,6 +78,8 @@
     Must,
     Pattern,
     Revision,
+    SCase,
+    SChoice,
     SContainer,
     SLeaf,
     SLeafList,
@@ -156,6 +158,8 @@
     "RangeAdded",
     "RangeRemoved",
     "Revision",
+    "SCase",
+    "SChoice",
     "SContainer",
     "SLeaf",
     "SLeafList",

libyang/schema.py

@@ -1416,6 +1416,12 @@ def children(
 # -------------------------------------------------------------------------------------
 @SNode.register(SNode.CHOICE)
 class SChoice(SNode):
+    __slots__ = ("cdata_choice",)
+
+    def __init__(self, context: "libyang.Context", cdata):
+        super().__init__(context, cdata)
+        self.cdata_choice = ffi.cast("struct lysc_node_choice *", cdata)
+
     def __iter__(self) -> Iterator[SNode]:
         return self.children()
 
@@ -1424,6 +1430,11 @@ def children(
     ) -> Iterator[SNode]:
         return iter_children(self.context, self.cdata, types=types, with_case=with_case)
 
+    def default(self) -> Optional[SNode]:
+        if self.cdata_choice.dflt == ffi.NULL:
+            return None
+        return SNode.new(self.context, self.cdata_choice.dflt)
+
 
 # -------------------------------------------------------------------------------------
 @SNode.register(SNode.CASE)

tests/test_schema.py

@@ -15,6 +15,8 @@
     Must,
     Pattern,
     Revision,
+    SCase,
+    SChoice,
     SContainer,
     SLeaf,
     SLeafList,
@@ -584,3 +586,20 @@ def test_leaf_list_min_max(self):
         self.assertIsInstance(leaflist2, SLeafList)
         self.assertEqual(leaflist2.min_elements(), 0)
         self.assertEqual(leaflist2.max_elements(), None)
+
+
+# -------------------------------------------------------------------------------------
+class ChoiceTest(unittest.TestCase):
+    def setUp(self):
+        self.ctx = Context(YANG_DIR)
+        self.ctx.load_module("yolo-system")
+
+    def tearDown(self):
+        self.ctx.destroy()
+        self.ctx = None
+
+    def test_choice_default(self):
+        conf = next(self.ctx.find_path("/yolo-system:conf"))
+        choice = next(conf.children((SNode.CHOICE,), with_choice=True))
+        self.assertIsInstance(choice, SChoice)
+        self.assertIsInstance(choice.default(), SCase)

tests/yang/yolo/yolo-system.yang

@@ -72,6 +72,7 @@ module yolo-system {
           type boolean;
         }
       }
+      default red;
     }
 
     list url {