main: inline Session._matchnodes() into Session.matchnodes()

Similar to the previous commit, this makes things more straightforward.

src/_pytest/main.py

@@ -709,19 +709,10 @@ class Session(nodes.FSCollector):
     ) -> Sequence[Union[nodes.Item, nodes.Collector]]:
         self.trace("matchnodes", matching, names)
         self.trace.root.indent += 1
-        nodes = self._matchnodes(matching, names)
-        num = len(nodes)
-        self.trace("matchnodes finished -> ", num, "nodes")
-        self.trace.root.indent -= 1
-        if num == 0:
-            raise NoMatch(matching, names[:1])
-        return nodes
 
-    def _matchnodes(
-        self, matching: Sequence[Union[nodes.Item, nodes.Collector]], names: List[str],
-    ) -> Sequence[Union[nodes.Item, nodes.Collector]]:
         if not matching or not names:
-            return matching
+            result = matching
+        else:
             name = names[0]
             assert name
             nextnames = names[1:]
@@ -754,7 +745,15 @@ class Session(nodes.FSCollector):
                     # specified in the command line because the module could not be
                     # imported (#134).
                     node.ihook.pytest_collectreport(report=rep)
-        return resultnodes
+            result = resultnodes
+
+        self.trace("matchnodes finished -> ", len(result), "nodes")
+        self.trace.root.indent -= 1
+
+        if not result:
+            raise NoMatch(matching, names[:1])
+        else:
+            return result
 
     def genitems(
         self, node: Union[nodes.Item, nodes.Collector]