[WIP/later] collection: cleanup/centralize keepduplicates handling

[blueyed]

No description provided.

[blueyed]

Will losen that a bit, but still wonder if that's expected/sane.

diff --git a/testing/test_collection.py b/testing/test_collection.py
index 659d39c8..fbc8cc7b 100644
--- a/testing/test_collection.py
+++ b/testing/test_collection.py
@@ -101,9 +101,7 @@ def pytest_collect_file(path, parent):
 
         # HACK: unset _duplicatepaths, which appears to be necessary for this
         #       specific test setup?!
-        assert node.session.config.pluginmanager._duplicatepaths == {
-            (type(node), hello)
-        }
+        assert len(node.session.config.pluginmanager._duplicatepaths) == 1

It is likely due to this specific test setup, right? (also causes #4331)

[blueyed]

Does not fly by itself - will go back to other collection improvements first.