-k should not match session name

Fixes pytest-dev#7040.

changelog/7040.improvement.rst

@@ -0,0 +1 @@
+``-k`` no longer matches against the directory containing the test suite.

src/_pytest/mark/__init__.py

@@ -136,7 +136,7 @@ def from_item(cls, item: "Item") -> "KeywordMatcher":
         import pytest
 
         for item in item.listchain():
-            if not isinstance(item, pytest.Instance):
+            if not isinstance(item, (pytest.Instance, pytest.Session)):
                 mapped_names.add(item.name)
 
         # Add the names added as extra keywords to current or parent items

testing/test_mark.py

@@ -814,25 +814,26 @@ def test_one():
         passed, skipped, failed = reprec.countoutcomes()
         assert passed + skipped + failed == 0
 
-    @pytest.mark.parametrize(
-        "keyword", ["__", "+", ".."],
-    )
-    def test_no_magic_values(self, testdir, keyword: str) -> None:
-        """Make sure the tests do not match on magic values,
-        no double underscored values, like '__dict__' and '+'.
-        """
-        p = testdir.makepyfile(
-            """
-            def test_one(): assert 1
+    def test_values_that_should_not_match(self, testdir) -> None:
+        """Some values should not ever be matched by -k
         """
-        )
-
-        reprec = testdir.inline_run("-k", keyword, p)
-        passed, skipped, failed = reprec.countoutcomes()
-        dlist = reprec.getcalls("pytest_deselected")
-        assert passed + skipped + failed == 0
-        deselected_tests = dlist[0].items
-        assert len(deselected_tests) == 1
+        p = testdir.makepyfile("def test_one(self): assert 1")
+
+        def assert_test_is_not_selected(keyword):
+            reprec = testdir.inline_run("-k", keyword, p)
+            passed, skipped, failed = reprec.countoutcomes()
+            dlist = reprec.getcalls("pytest_deselected")
+            assert passed + skipped + failed == 0
+            deselected_tests = dlist[0].items
+            assert len(deselected_tests) == 1
+
+        # should not match dunder objects
+        assert_test_is_not_selected("__")
+        # should not match against invalid expressions
+        assert_test_is_not_selected("+")
+        assert_test_is_not_selected("..")
+        # should not match against session
+        assert_test_is_not_selected(testdir.tmpdir.basename)
 
 
 class TestMarkDecorator: