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libyang3-py3: patch for backlinks support
CESNET/libyang-python#132
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‎src/libyang3-py3/patch/0004-pr132-backlinks.patch

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From ebb79c5fec9635b5efb7a24daf1537ba91491f6a Mon Sep 17 00:00:00 2001
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From: Brad House <brad@brad-house.com>
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Date: Sun, 16 Feb 2025 11:04:50 -0500
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Subject: [PATCH] schema/context: restore some backlinks support
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In libyang v1 the schema nodes had a backlinks member to be able to
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look up dependents of the node. SONiC depends on this to provide
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functionality it uses and it needs to be exposed via the python
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module.
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In theory, exposing the 'dfs' functions could make this work, but
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it would likely be cost prohibitive since walking the tree would
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be expensive to create a python node for evaluation in native
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python.
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Instead this PR depends on the this libyang PR:
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https://github.com/CESNET/libyang/pull/2352
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And adds thin wrappers.
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This implementation provides 2 python functions:
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* Context.find_backlinks_paths() - This function can
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take the path of the base node and find all dependents. If
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no path is specified, then it will return all nodes that contain
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a leafref reference.
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* Context.find_leafref_path_target_paths() - This function takes
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an xpath, then returns all target nodes the xpath may reference.
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Typically only one will be returned, but multiples may be in the
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case of a union.
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A user can build a cache by combining Context.find_backlinks_paths()
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with no path set and building a reverse table using
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Context.find_leafref_path_target_paths()
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Signed-off-by: Brad House <brad@brad-house.com>
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---
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cffi/cdefs.h | 2 +
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libyang/context.py | 98 +++++++++++++++++++
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tests/test_schema.py | 58 +++++++++++
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.../yang/yolo/yolo-leafref-search-extmod.yang | 39 ++++++++
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tests/yang/yolo/yolo-leafref-search.yang | 36 +++++++
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5 files changed, 233 insertions(+)
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create mode 100644 tests/yang/yolo/yolo-leafref-search-extmod.yang
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create mode 100644 tests/yang/yolo/yolo-leafref-search.yang
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diff --git a/cffi/cdefs.h b/cffi/cdefs.h
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index aa75004..e7dc978 100644
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--- a/cffi/cdefs.h
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+++ b/cffi/cdefs.h
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@@ -861,6 +861,8 @@ const struct lysc_node* lys_find_child(const struct lysc_node *, const struct ly
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const struct lysc_node* lysc_node_child(const struct lysc_node *);
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const struct lysc_node_action* lysc_node_actions(const struct lysc_node *);
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const struct lysc_node_notif* lysc_node_notifs(const struct lysc_node *);
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+LY_ERR lysc_node_lref_targets(const struct lysc_node *, struct ly_set **);
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+LY_ERR lysc_node_lref_backlinks(const struct ly_ctx *, const struct lysc_node *, ly_bool, struct ly_set **);
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typedef enum {
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LYD_PATH_STD,
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diff --git a/libyang/context.py b/libyang/context.py
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index fb4a330..d6eb7a3 100644
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--- a/libyang/context.py
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+++ b/libyang/context.py
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@@ -646,6 +646,104 @@ def parse_data_file(
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json_null=json_null,
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)
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+ def find_leafref_path_target_paths(self, leafref_path: str) -> list[str]:
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+ """
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+ Fetch all leafref targets of the specified path
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+
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+ This is an enhanced version of lysc_node_lref_target() which will return
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+ a set of leafref target paths retrieved from the specified schema path.
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+ While lysc_node_lref_target() will only work on nodetype of LYS_LEAF and
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+ LYS_LEAFLIST this function will also evaluate other datatypes that may
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+ contain leafrefs such as LYS_UNION. This does not, however, search for
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+ children with leafref targets.
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+
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+ :arg self
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+ This instance on context
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+ :arg leafref_path:
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+ Path to node to search for leafref targets
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+ :returns List of target paths that the leafrefs of the specified node
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+ point to.
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+ """
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+ if self.cdata is None:
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+ raise RuntimeError("context already destroyed")
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+ if leafref_path is None:
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+ raise RuntimeError("leafref_path must be defined")
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+
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+ out = []
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+
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+ node = lib.lys_find_path(self.cdata, ffi.NULL, str2c(leafref_path), 0)
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+ if node == ffi.NULL:
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+ raise self.error("leafref_path not found")
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+
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+ node_set = ffi.new("struct ly_set **")
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+ if (lib.lysc_node_lref_targets(node, node_set) != lib.LY_SUCCESS or
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+ node_set[0] == ffi.NULL or node_set[0].count == 0):
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+ raise self.error("leafref_path does not contain any leafref targets")
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+
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+ node_set = node_set[0]
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+ for i in range(node_set.count):
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+ path = lib.lysc_path(node_set.snodes[i], lib.LYSC_PATH_DATA, ffi.NULL, 0);
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+ out.append(c2str(path))
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+ lib.free(path)
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+
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+ lib.ly_set_free(node_set, ffi.NULL)
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+
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+ return out
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+
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+
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+ def find_backlinks_paths(self, match_path: str = None, match_ancestors: bool = False) -> list[str]:
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+ """
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+ Search entire schema for nodes that contain leafrefs and return as a
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+ list of schema node paths.
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+
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+ Perform a complete scan of the schema tree looking for nodes that
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+ contain leafref entries. When a node contains a leafref entry, and
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+ match_path is specified, determine if reference points to match_path,
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+ if so add the node's path to returned list. If no match_path is
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+ specified, the node containing the leafref is always added to the
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+ returned set. When match_ancestors is true, will evaluate if match_path
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+ is self or an ansestor of self.
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+
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+ This does not return the leafref targets, but the actual node that
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+ contains a leafref.
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+
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+ :arg self
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+ This instance on context
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+ :arg match_path:
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+ Target path to use for matching
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+ :arg match_ancestors:
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+ Whether match_path is a base ancestor or an exact node
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+ :returns List of paths. Exception of match_path is not found or if no
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+ backlinks are found.
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+ """
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+ if self.cdata is None:
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+ raise RuntimeError("context already destroyed")
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+ out = []
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+
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+ match_node = ffi.NULL
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+ if match_path is not None and match_path == "/" or match_path == "":
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+ match_path = None
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+
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+ if match_path:
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+ match_node = lib.lys_find_path(self.cdata, ffi.NULL, str2c(match_path), 0)
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+ if match_node == ffi.NULL:
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+ raise self.error("match_path not found")
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+
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+ node_set = ffi.new("struct ly_set **")
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+ if (lib.lysc_node_lref_backlinks(self.cdata, match_node, match_ancestors, node_set)
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+ != lib.LY_SUCCESS or node_set[0] == ffi.NULL or node_set[0].count == 0):
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+ raise self.error("backlinks not found")
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+
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+ node_set = node_set[0]
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+ for i in range(node_set.count):
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+ path = lib.lysc_path(node_set.snodes[i], lib.LYSC_PATH_DATA, ffi.NULL, 0);
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+ out.append(c2str(path))
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+ lib.free(path)
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+
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+ lib.ly_set_free(node_set, ffi.NULL)
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+
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+ return out
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+
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def __iter__(self) -> Iterator[Module]:
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"""
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Return an iterator that yields all implemented modules from the context
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diff --git a/tests/test_schema.py b/tests/test_schema.py
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index a310aad..4aae73a 100644
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--- a/tests/test_schema.py
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+++ b/tests/test_schema.py
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@@ -801,6 +801,64 @@ def test_leaf_list_parsed(self):
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self.assertFalse(pnode.ordered())
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+# -------------------------------------------------------------------------------------
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+class BacklinksTest(unittest.TestCase):
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+ def setUp(self):
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+ self.ctx = Context(YANG_DIR)
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+ self.ctx.load_module("yolo-leafref-search")
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+ self.ctx.load_module("yolo-leafref-search-extmod")
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+ def tearDown(self):
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+ self.ctx.destroy()
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+ self.ctx = None
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+ def test_backlinks_all_nodes(self):
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+ expected = [
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+ "/yolo-leafref-search-extmod:my_extref_list/my_extref",
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+ "/yolo-leafref-search:refstr",
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+ "/yolo-leafref-search:refnum",
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+ "/yolo-leafref-search-extmod:my_extref_list/my_extref_union"
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+ ]
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+ refs = self.ctx.find_backlinks_paths()
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+ expected.sort()
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+ refs.sort()
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+ self.assertEqual(expected, refs)
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+ def test_backlinks_one(self):
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+ expected = [
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+ "/yolo-leafref-search-extmod:my_extref_list/my_extref",
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+ "/yolo-leafref-search:refstr",
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+ "/yolo-leafref-search-extmod:my_extref_list/my_extref_union"
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+ ]
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+ refs = self.ctx.find_backlinks_paths(
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+ match_path="/yolo-leafref-search:my_list/my_leaf_string"
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+ )
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+ expected.sort()
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+ refs.sort()
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+ self.assertEqual(expected, refs)
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+ def test_backlinks_children(self):
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+ expected = [
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+ "/yolo-leafref-search-extmod:my_extref_list/my_extref",
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+ "/yolo-leafref-search:refstr",
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+ "/yolo-leafref-search:refnum",
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+ "/yolo-leafref-search-extmod:my_extref_list/my_extref_union"
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+ ]
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+ refs = self.ctx.find_backlinks_paths(
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+ match_path="/yolo-leafref-search:my_list",
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+ match_ancestors=True
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+ )
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+ expected.sort()
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+ refs.sort()
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+ self.assertEqual(expected, refs)
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+ def test_backlinks_leafref_target_paths(self):
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+ expected = [
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+ "/yolo-leafref-search:my_list/my_leaf_string"
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+ ]
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+ refs = self.ctx.find_leafref_path_target_paths(
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+ "/yolo-leafref-search-extmod:my_extref_list/my_extref"
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+ )
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+ expected.sort()
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+ refs.sort()
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+ self.assertEqual(expected, refs)
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+
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+
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# -------------------------------------------------------------------------------------
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class ChoiceTest(unittest.TestCase):
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def setUp(self):
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diff --git a/tests/yang/yolo/yolo-leafref-search-extmod.yang b/tests/yang/yolo/yolo-leafref-search-extmod.yang
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new file mode 100644
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index 0000000..046ceec
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--- /dev/null
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+++ b/tests/yang/yolo/yolo-leafref-search-extmod.yang
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@@ -0,0 +1,39 @@
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+module yolo-leafref-search-extmod {
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+ yang-version 1.1;
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+ namespace "urn:yang:yolo:leafref-search-extmod";
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+ prefix leafref-search-extmod;
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+
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+ import wtf-types { prefix types; }
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+
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+ import yolo-leafref-search {
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+ prefix leafref-search;
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+ }
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+
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+ revision 2025-02-11 {
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+ description
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+ "Initial version.";
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+ }
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+
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+ list my_extref_list {
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+ key my_leaf_string;
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+ leaf my_leaf_string {
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+ type string;
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+ }
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+ leaf my_extref {
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+ type leafref {
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+ path "/leafref-search:my_list/leafref-search:my_leaf_string";
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+ }
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+ }
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+ leaf my_extref_union {
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+ type union {
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+ type leafref {
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+ path "/leafref-search:my_list/leafref-search:my_leaf_string";
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+ }
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+ type leafref {
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+ path "/leafref-search:my_list/leafref-search:my_leaf_number";
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+ }
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+ type types:number;
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+ }
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+ }
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+ }
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+}
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diff --git a/tests/yang/yolo/yolo-leafref-search.yang b/tests/yang/yolo/yolo-leafref-search.yang
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new file mode 100644
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index 0000000..5f4af48
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--- /dev/null
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+++ b/tests/yang/yolo/yolo-leafref-search.yang
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@@ -0,0 +1,36 @@
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+module yolo-leafref-search {
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+ yang-version 1.1;
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+ namespace "urn:yang:yolo:leafref-search";
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+ prefix leafref-search;
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+
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+ import wtf-types { prefix types; }
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+
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+ revision 2025-02-11 {
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+ description
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+ "Initial version.";
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+ }
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+
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+ list my_list {
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+ key my_leaf_string;
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+ leaf my_leaf_string {
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+ type string;
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+ }
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+ leaf my_leaf_number {
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+ description
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+ "A number.";
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+ type types:number;
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+ }
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+ }
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+
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+ leaf refstr {
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+ type leafref {
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+ path "../my_list/my_leaf_string";
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+ }
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+ }
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+
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+ leaf refnum {
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+ type leafref {
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+ path "../my_list/my_leaf_number";
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+ }
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+ }
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+}

‎src/libyang3-py3/patch/series

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0001-debian.patch
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0002-pr134-json-string-datatypes.patch
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0003-parse_module-memleak.patch
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0004-pr132-backlinks.patch

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