From ba407b5eb601da54a893df769fd61e65a718bb66 Mon Sep 17 00:00:00 2001
From: Bruno Oliveira <nicoddemus@gmail.com>
Date: Wed, 4 Apr 2018 20:36:07 -0300
Subject: [PATCH] Clear sys.last_* attributes before running an item

Otherwise we will keep the last failed exception around forever

Related to #2798
---
 _pytest/runner.py      |  3 ++-
 testing/test_runner.py | 19 ++++++++++++++-----
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/_pytest/runner.py b/_pytest/runner.py
index 6792387db..f62d34df2 100644
--- a/_pytest/runner.py
+++ b/_pytest/runner.py
@@ -105,6 +105,7 @@ def pytest_runtest_setup(item):
 
 def pytest_runtest_call(item):
     _update_current_test_var(item, 'call')
+    sys.last_type, sys.last_value, sys.last_traceback = (None, None, None)
     try:
         item.runtest()
     except Exception:
@@ -114,7 +115,7 @@ def pytest_runtest_call(item):
         sys.last_type = type
         sys.last_value = value
         sys.last_traceback = tb
-        del tb  # Get rid of it in this namespace
+        del type, value, tb  # Get rid of these in this frame
         raise
 
 
diff --git a/testing/test_runner.py b/testing/test_runner.py
index a3bd8ecb4..7c179b1f2 100644
--- a/testing/test_runner.py
+++ b/testing/test_runner.py
@@ -719,18 +719,20 @@ def test_makereport_getsource_dynamic_code(testdir, monkeypatch):
     result.stdout.fnmatch_lines(["*test_fix*", "*fixture*'missing'*not found*"])
 
 
-def test_store_except_info_on_eror():
+def test_store_except_info_on_error():
     """ Test that upon test failure, the exception info is stored on
     sys.last_traceback and friends.
     """
-    # Simulate item that raises a specific exception
-    class ItemThatRaises(object):
+    # Simulate item that might raise a specific exception, depending on `raise_error` class var
+    class ItemMightRaise(object):
         nodeid = 'item_that_raises'
+        raise_error = True
 
         def runtest(self):
-            raise IndexError('TEST')
+            if self.raise_error:
+                raise IndexError('TEST')
     try:
-        runner.pytest_runtest_call(ItemThatRaises())
+        runner.pytest_runtest_call(ItemMightRaise())
     except IndexError:
         pass
     # Check that exception info is stored on sys
@@ -738,6 +740,13 @@ def test_store_except_info_on_eror():
     assert sys.last_value.args[0] == 'TEST'
     assert sys.last_traceback
 
+    # The next run should clear the exception info stored by the previous run
+    ItemMightRaise.raise_error = False
+    runner.pytest_runtest_call(ItemMightRaise())
+    assert sys.last_type is None
+    assert sys.last_value is None
+    assert sys.last_traceback is None
+
 
 def test_current_test_env_var(testdir, monkeypatch):
     pytest_current_test_vars = []