From 9a91b67eeb3550142f8a6e4b093e59140ddc9320 Mon Sep 17 00:00:00 2001
From: Bruno Oliveira <nicoddemus@gmail.com>
Date: Tue, 25 Aug 2020 19:48:26 -0300
Subject: [PATCH] Merge pull request #7687 from bluetech/idval-notset

python: fix empty parametrize() leading to "NotSetType.token" id
---
 changelog/7686.bugfix.rst  | 2 ++
 src/_pytest/python.py      | 3 +++
 testing/python/metafunc.py | 9 +++++++++
 3 files changed, 14 insertions(+)
 create mode 100644 changelog/7686.bugfix.rst

diff --git a/changelog/7686.bugfix.rst b/changelog/7686.bugfix.rst
new file mode 100644
index 00000000000..8549fae8eb1
--- /dev/null
+++ b/changelog/7686.bugfix.rst
@@ -0,0 +1,2 @@
+Fixed `NotSetType.token` being used as the parameter ID when the parametrization list is empty.
+Regressed in pytest 6.0.0.
diff --git a/src/_pytest/python.py b/src/_pytest/python.py
index aa817148683..28c2dc849c7 100644
--- a/src/_pytest/python.py
+++ b/src/_pytest/python.py
@@ -1254,6 +1254,9 @@ def _idval(
         return str(val)
     elif isinstance(val, REGEX_TYPE):
         return ascii_escaped(val.pattern)
+    elif val is NOTSET:
+        # Fallback to default. Note that NOTSET is an enum.Enum.
+        pass
     elif isinstance(val, enum.Enum):
         return str(val)
     elif isinstance(getattr(val, "__name__", None), str):
diff --git a/testing/python/metafunc.py b/testing/python/metafunc.py
index 4e6cfaf91ba..5d935153931 100644
--- a/testing/python/metafunc.py
+++ b/testing/python/metafunc.py
@@ -19,6 +19,7 @@
 import pytest
 from _pytest import fixtures
 from _pytest import python
+from _pytest.compat import NOTSET
 from _pytest.outcomes import fail
 from _pytest.pytester import Testdir
 from _pytest.python import _idval
@@ -363,6 +364,14 @@ def test_function():
         for val, expected in values:
             assert _idval(val, "a", 6, None, nodeid=None, config=None) == expected
 
+    def test_notset_idval(self) -> None:
+        """Test that a NOTSET value (used by an empty parameterset) generates
+        a proper ID.
+
+        Regression test for #7686.
+        """
+        assert _idval(NOTSET, "a", 0, None, nodeid=None, config=None) == "a0"
+
     def test_idmaker_autoname(self) -> None:
         """#250"""
         result = idmaker(