From 24226c24e11e6bcdbbf7f63446911baa827a0db8 Mon Sep 17 00:00:00 2001
From: nvxf <68589039+nvxf@users.noreply.github.com>
Date: Mon, 22 Jan 2024 11:23:47 +0100
Subject: [PATCH] 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>
---
 libyang/data.py    | 22 ++++++++++++++++------
 tests/test_data.py | 11 +++++++++++
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/libyang/data.py b/libyang/data.py
index 69649eba..ff98dbf8 100644
--- a/libyang/data.py
+++ b/libyang/data.py
@@ -404,11 +404,7 @@ 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,
@@ -904,11 +900,25 @@ 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)
diff --git a/tests/test_data.py b/tests/test_data.py
index becb5d0c..7b3a7aa7 100644
--- a/tests/test_data.py
+++ b/tests/test_data.py
@@ -860,3 +860,14 @@ def test_add_defaults(self):
         node = dnode.find_path("/yolo-system:conf/speed")
         self.assertIsInstance(node, DLeaf)
         self.assertEqual(node.value(), 4321)
+
+    def test_dnode_new_opaq_find_one(self):
+        dnode = self.ctx.parse_data_mem(self.JSON_CONFIG, "json", validate_present=True)
+
+        hostname = dnode.find_one("hostname")
+        hostname.free(with_siblings=False)
+
+        dnode.new_path("/yolo-system:conf/hostname", value=None, opt_opaq=True)
+        opaq_hostname = dnode.find_one("hostname")
+
+        self.assertIsInstance(opaq_hostname, DLeaf)