data: add leafref_nodes and leafref_link_node_tree

This patch adds API, which allows user to:
 - determine if DNode is being referenced by some other leafref DNodes.
 - trigger process for creating cross-references between leafref DNodes
   and target DNodes.

Closes: #108
Signed-off-by: Stefan Gula <[email protected]>
Signed-off-by: Samuel Gauthier <[email protected]>

cffi/cdefs.h

@@ -1248,5 +1248,14 @@ struct lyd_attr {
 LY_ERR lyd_new_attr(struct lyd_node *, const char *, const char *, const char *, struct lyd_attr **);
 void lyd_free_attr_single(const struct ly_ctx *ctx, struct lyd_attr *attr);
 
+struct lyd_leafref_links_rec {
+    const struct lyd_node_term *node;
+    const struct lyd_node_term **leafref_nodes;
+    const struct lyd_node_term **target_nodes;
+};
+
+LY_ERR lyd_leafref_get_links(const struct lyd_node_term *e, const struct lyd_leafref_links_rec **);
+LY_ERR lyd_leafref_link_node_tree(struct lyd_node *);
+
 /* from libc, needed to free allocated strings */
 void free(void *);

libyang/data.py

@@ -18,7 +18,7 @@
     SRpc,
     Type,
 )
-from .util import DataType, IOType, LibyangError, c2str, str2c
+from .util import DataType, IOType, LibyangError, c2str, ly_array_iter, str2c
 
 
 LOG = logging.getLogger(__name__)
@@ -991,6 +991,28 @@ def free(self, with_siblings: bool = True) -> None:
         finally:
             self.cdata = ffi.NULL
 
+    def leafref_link_node_tree(self) -> None:
+        """
+        Traverse through data tree including root node siblings and adds
+        leafrefs links to the given nodes.
+
+        Requires leafref_linking to be set on the libyang context.
+        """
+        lib.lyd_leafref_link_node_tree(self.cdata)
+
+    def leafref_nodes(self) -> Iterator["DNode"]:
+        """
+        Gets the leafref links record for given node.
+
+        Requires leafref_linking to be set on the libyang context.
+        """
+        term_node = ffi.cast("struct lyd_node_term *", self.cdata)
+        out = ffi.new("const struct lyd_leafref_links_rec **")
+        if lib.lyd_leafref_get_links(term_node, out) != lib.LY_SUCCESS:
+            return
+        for n in ly_array_iter(out[0].leafref_nodes):
+            yield DNode.new(self.context, n)
+
     def __repr__(self):
         cls = self.__class__
         return "<%s.%s: %s>" % (cls.__module__, cls.__name__, str(self))

tests/test_data.py

@@ -21,6 +21,7 @@
     DRpc,
     IOType,
     LibyangError,
+    Module,
 )
 from libyang.data import dict_to_dnode
 
@@ -1066,3 +1067,28 @@ def test_dnode_attrs_set_and_remove_multiple(self):
 
         attrs.remove("ietf-netconf:operation")
         self.assertEqual(len(attrs), 0)
+
+    def test_dnode_leafref_linking(self):
+        MAIN = """{
+            "yolo-leafref-extended:list1": [{
+                "leaf1": "val1",
+                "leaflist2": ["val2", "val3"]
+            }],
+            "yolo-leafref-extended:ref1": "val1"
+            }"""
+        self.ctx.destroy()
+        self.ctx = Context(YANG_DIR, leafref_extended=True, leafref_linking=True)
+        mod = self.ctx.load_module("yolo-leafref-extended")
+        self.assertIsInstance(mod, Module)
+        dnode1 = self.ctx.parse_data_mem(MAIN, "json", parse_only=True)
+        self.assertIsInstance(dnode1, DList)
+        dnode2 = next(dnode1.siblings(include_self=False))
+        self.assertIsInstance(dnode2, DLeaf)
+        dnode3 = next(dnode1.children())
+        self.assertIsInstance(dnode3, DLeaf)
+        self.assertIsNone(next(dnode3.leafref_nodes(), None))
+        dnode2.leafref_link_node_tree()
+        dnode4 = next(dnode3.leafref_nodes())
+        self.assertIsInstance(dnode4, DLeaf)
+        self.assertEqual(dnode4.cdata, dnode2.cdata)
+        dnode1.free()