From 9cf4a825141bc2039647937e4db1c40b94394b00 Mon Sep 17 00:00:00 2001
From: Daniel Hahler <git@thequod.de>
Date: Tue, 12 Nov 2019 15:47:41 +0100
Subject: [PATCH] adjust test_parametrized_ids_invalid_type, create list to
 convert tuples

Ref: https://github.com/pytest-dev/pytest/issues/1857#issuecomment-552922498
---
 src/_pytest/python.py      | 10 +++++-----
 testing/python/metafunc.py |  7 ++++---
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/_pytest/python.py b/src/_pytest/python.py
index bf350ed643a..932a20799a6 100644
--- a/src/_pytest/python.py
+++ b/src/_pytest/python.py
@@ -1030,7 +1030,7 @@ def _resolve_arg_ids(self, argnames, ids, parameters, item):
 
     def _validate_ids(self, ids, parameters, func_name):
         try:
-            len_ids = len(ids)
+            len(ids)
         except TypeError:
             try:
                 it = iter(ids)
@@ -1039,13 +1039,13 @@ def _validate_ids(self, ids, parameters, func_name):
             else:
                 import itertools
 
-                ids = list(itertools.islice(it, len(parameters)))
-                len_ids = len(ids)
+                new_ids = list(itertools.islice(it, len(parameters)))
+        else:
+            new_ids = list(ids)
 
-        if len_ids != len(parameters):
+        if len(new_ids) != len(parameters):
             msg = "In {}: {} parameter sets specified, with different number of ids: {}"
             fail(msg.format(func_name, len(parameters), len(ids)), pytrace=False)
-        new_ids = ids[:]
         for idx, id_value in enumerate(new_ids):
             if id_value is not None:
                 if isinstance(id_value, int):
diff --git a/testing/python/metafunc.py b/testing/python/metafunc.py
index 8a63ca77b8e..f23158ff4a7 100644
--- a/testing/python/metafunc.py
+++ b/testing/python/metafunc.py
@@ -1186,12 +1186,12 @@ def test_temp(temp):
         result.stdout.fnmatch_lines(["* 1 skipped *"])
 
     def test_parametrized_ids_invalid_type(self, testdir):
-        """Tests parametrized with ids as non-strings (#1857)."""
+        """Test error with non-strings/non-ints, without generator (#1857)."""
         testdir.makepyfile(
             """
             import pytest
 
-            @pytest.mark.parametrize("x, expected", [(10, 20), (40, 80)], ids=(None, 2))
+            @pytest.mark.parametrize("x, expected", [(1, 2), (3, 4), (5, 6)], ids=(None, 2, type))
             def test_ids_numbers(x,expected):
                 assert x * 2 == expected
         """
@@ -1199,7 +1199,8 @@ def test_ids_numbers(x,expected):
         result = testdir.runpytest()
         result.stdout.fnmatch_lines(
             [
-                "*In test_ids_numbers: ids must be list of strings, found: 2 (type: *'int'>)*"
+                "In test_ids_numbers: ids must be list of strings, "
+                "found: <class 'type'> (type: <class 'type'>) at index 2"
             ]
         )