fix #4649 - also transfer markers to keywordmapping

as it turns out it is distinct from nodekeywords and behaves completely different

changelog/4649.bugfix.rst

@@ -0,0 +1 @@
+Restore marks being considered keywords for keyword expressions.

src/_pytest/mark/legacy.py

@@ -45,13 +45,14 @@ class KeywordMapping(object):
                 mapped_names.add(item.name)
 
         # Add the names added as extra keywords to current or parent items
-        for name in item.listextrakeywords():
+        mapped_names.update(item.listextrakeywords())
-            mapped_names.add(name)
 
         # Add the names attached to the current function through direct assignment
         if hasattr(item, "function"):
-            for name in item.function.__dict__:
+            mapped_names.update(item.function.__dict__)
-                mapped_names.add(name)
+
+        # add the markers to the keywords as we no longer handle them correctly
+        mapped_names.update(mark.name for mark in item.iter_markers())
 
         return cls(mapped_names)
 

testing/example_scripts/marks/marks_considered_keywords/test_marks_as_keywords.py

@@ -0,0 +1,6 @@
+import pytest
+
+
+@pytest.mark.foo
+def test_mark():
+    pass

testing/test_mark.py

@@ -292,6 +292,13 @@ def test_keyword_option_custom(spec, testdir):
     assert list(passed) == list(passed_result)
 
 
+def test_keyword_option_considers_mark(testdir):
+    testdir.copy_example("marks/marks_considered_keywords")
+    rec = testdir.inline_run("-k", "foo")
+    passed = rec.listoutcomes()[0]
+    assert len(passed) == 1
+
+
 @pytest.mark.parametrize(
     "spec",
     [