data: fix DNode.new schema handling

In case of a call to DNode.new with cdata containing an opaque node
the new method tries to access cdata.schema.nodetype, which results
in a NULL pointer dereference.

To get the schema for an opaque node retrieve the schema from the
context using the path of the node.

Fixes: #73
Signed-off-by: nvxf <68589039+nvxf@users.noreply.github.com>
Acked-by: Samuel Gauthier <samuel.gauthier@6wind.com>

Author: nvxf

libyang/data.py

@@ -417,11 +417,7 @@ def eval_xpath(self, xpath: str):
         return False
 
     def path(self) -> str:
-        path = lib.lyd_path(self.cdata, lib.LYD_PATH_STD, ffi.NULL, 0)
-        try:
-            return c2str(path)
-        finally:
-            lib.free(path)
+        return self._get_path(self.cdata)
 
     def validate(
         self,
@@ -923,11 +919,25 @@ def _decorator(nodeclass):
     @classmethod
     def new(cls, context: "libyang.Context", cdata) -> "DNode":
         cdata = ffi.cast("struct lyd_node *", cdata)
-        nodecls = cls.NODETYPE_CLASS.get(cdata.schema.nodetype, None)
+        if not cdata.schema:
+            schemas = list(context.find_path(cls._get_path(cdata)))
+            if len(schemas) != 1:
+                raise LibyangError("Unable to determine schema")
+            nodecls = cls.NODETYPE_CLASS.get(schemas[0].nodetype(), None)
+        else:
+            nodecls = cls.NODETYPE_CLASS.get(cdata.schema.nodetype, None)
         if nodecls is None:
             raise TypeError("node type %s not implemented" % cdata.schema.nodetype)
         return nodecls(context, cdata)
 
+    @staticmethod
+    def _get_path(cdata) -> str:
+        path = lib.lyd_path(cdata, lib.LYD_PATH_STD, ffi.NULL, 0)
+        try:
+            return c2str(path)
+        finally:
+            lib.free(path)
+
 
 # -------------------------------------------------------------------------------------
 @DNode.register(SNode.CONTAINER)

tests/test_data.py

@@ -949,3 +949,14 @@ def test_dnode_insert_sibling(self):
         sibling = next(dnode1.siblings(include_self=False), None)
         self.assertIsInstance(sibling, DLeaf)
         self.assertEqual(sibling.cdata, dnode2.cdata)
+
+    def test_dnode_new_opaq_find_one(self):
+        root = self.ctx.create_data_path(path="/yolo-system:conf")
+        root.new_path(
+            "hostname",
+            None,
+            opt_opaq=True,
+        )
+        dnode = root.find_one("/yolo-system:conf/hostname")
+
+        self.assertIsInstance(dnode, DLeaf)