nodes: add Node.iterchain() function

This is a useful addition to the existing `listchain`. While `listchain`
returns top-to-bottom, `iterchain` is bottom-to-top and doesn't require
an internal full iteration + `reverse`.

Author: bluetech

changelog/11801.improvement.rst

@@ -0,0 +1,2 @@
+Added the :func:`iterchain() <_pytest.nodes.Node.iterchain>` helper method on nodes.
+It is similar to :func:`listchain <_pytest.nodes.Node.listchain>`, but goes from bottom to top, and returns an iterator, not a list.

src/_pytest/fixtures.py

@@ -1513,7 +1513,7 @@ def pytest_plugin_registered(self, plugin: _PluggyPlugin) -> None:
 
     def _getautousenames(self, node: nodes.Node) -> Iterator[str]:
         """Return the names of autouse fixtures applicable to node."""
-        for parentnode in reversed(list(nodes.iterparentnodes(node))):
+        for parentnode in node.listchain():
             basenames = self._nodeid_autousenames.get(parentnode.nodeid)
             if basenames:
                 yield from basenames
@@ -1781,7 +1781,7 @@ def getfixturedefs(
     def _matchfactories(
         self, fixturedefs: Iterable[FixtureDef[Any]], node: nodes.Node
     ) -> Iterator[FixtureDef[Any]]:
-        parentnodeids = {n.nodeid for n in nodes.iterparentnodes(node)}
+        parentnodeids = {n.nodeid for n in node.iterchain()}
         for fixturedef in fixturedefs:
             if fixturedef.baseid in parentnodeids:
                 yield fixturedef

src/_pytest/nodes.py

@@ -49,15 +49,6 @@
 tracebackcutdir = Path(_pytest.__file__).parent
 
 
-def iterparentnodes(node: "Node") -> Iterator["Node"]:
-    """Return the parent nodes, including the node itself, from the node
-    upwards."""
-    parent: Optional[Node] = node
-    while parent is not None:
-        yield parent
-        parent = parent.parent
-
-
 _NodeType = TypeVar("_NodeType", bound="Node")
 
 
@@ -265,12 +256,20 @@ def setup(self) -> None:
     def teardown(self) -> None:
         pass
 
-    def listchain(self) -> List["Node"]:
-        """Return list of all parent collectors up to self, starting from
-        the root of collection tree.
+    def iterchain(self) -> Iterator["Node"]:
+        """Iterate over self and all parent collectors up to root of the
+        collection tree, starting from self.
 
-        :returns: The nodes.
+        .. versionadded:: 8.1
         """
+        parent: Optional[Node] = self
+        while parent is not None:
+            yield parent
+            parent = parent.parent
+
+    def listchain(self) -> List["Node"]:
+        """Return a list of all parent collectors up to and including self,
+        starting from the root of the collection tree."""
         chain = []
         item: Optional[Node] = self
         while item is not None:
@@ -319,7 +318,7 @@ def iter_markers_with_node(
         :param name: If given, filter the results by the name attribute.
         :returns: An iterator of (node, mark) tuples.
         """
-        for node in reversed(self.listchain()):
+        for node in self.iterchain():
             for mark in node.own_markers:
                 if name is None or getattr(mark, "name", None) == name:
                     yield node, mark
@@ -363,17 +362,16 @@ def addfinalizer(self, fin: Callable[[], object]) -> None:
         self.session._setupstate.addfinalizer(fin, self)
 
     def getparent(self, cls: Type[_NodeType]) -> Optional[_NodeType]:
-        """Get the next parent node (including self) which is an instance of
+        """Get the closest parent node (including self) which is an instance of
         the given class.
 
         :param cls: The node class to search for.
         :returns: The node, if found.
         """
-        current: Optional[Node] = self
-        while current and not isinstance(current, cls):
-            current = current.parent
-        assert current is None or isinstance(current, cls)
-        return current
+        for node in self.iterchain():
+            if isinstance(node, cls):
+                return node
+        return None
 
     def _traceback_filter(self, excinfo: ExceptionInfo[BaseException]) -> Traceback:
         return excinfo.traceback

src/_pytest/python.py

@@ -333,10 +333,8 @@ def _getobj(self):
 
     def getmodpath(self, stopatmodule: bool = True, includemodule: bool = False) -> str:
         """Return Python path relative to the containing module."""
-        chain = self.listchain()
-        chain.reverse()
         parts = []
-        for node in chain:
+        for node in self.iterchain():
             name = node.name
             if isinstance(node, Module):
                 name = os.path.splitext(name)[0]