From 557b9a52edc4445cec293f2cc2c268c4f564adcf Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Tue, 22 Sep 2020 16:16:46 +0300
Subject: [PATCH] bpo-40670: More reliable validation of statements in
 timeit.Timer. (GH-22358)

It now accepts "empty" statements (only whitespaces and comments)
and rejects misindentent statements.
---
 Lib/test/test_timeit.py                                  | 9 +++++++++
 Lib/timeit.py                                            | 1 +
 .../Library/2020-09-22-14-55-34.bpo-40670.R5sm68.rst     | 3 +++
 3 files changed, 13 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2020-09-22-14-55-34.bpo-40670.R5sm68.rst

diff --git a/Lib/test/test_timeit.py b/Lib/test/test_timeit.py
index e02d4a71a9b..72a104fc1a6 100644
--- a/Lib/test/test_timeit.py
+++ b/Lib/test/test_timeit.py
@@ -77,6 +77,9 @@ class TestTimeit(unittest.TestCase):
         self.assertRaises(SyntaxError, timeit.Timer, stmt='break')
         self.assertRaises(SyntaxError, timeit.Timer, stmt='continue')
         self.assertRaises(SyntaxError, timeit.Timer, stmt='from timeit import *')
+        self.assertRaises(SyntaxError, timeit.Timer, stmt='  pass')
+        self.assertRaises(SyntaxError, timeit.Timer,
+                          setup='while False:\n  pass', stmt='  break')
 
     def test_timer_invalid_setup(self):
         self.assertRaises(ValueError, timeit.Timer, setup=None)
@@ -86,6 +89,12 @@ class TestTimeit(unittest.TestCase):
         self.assertRaises(SyntaxError, timeit.Timer, setup='break')
         self.assertRaises(SyntaxError, timeit.Timer, setup='continue')
         self.assertRaises(SyntaxError, timeit.Timer, setup='from timeit import *')
+        self.assertRaises(SyntaxError, timeit.Timer, setup='  pass')
+
+    def test_timer_empty_stmt(self):
+        timeit.Timer(stmt='')
+        timeit.Timer(stmt=' \n\t\f')
+        timeit.Timer(stmt='# comment')
 
     fake_setup = "import timeit\ntimeit._fake_timer.setup()"
     fake_stmt = "import timeit\ntimeit._fake_timer.inc()"
diff --git a/Lib/timeit.py b/Lib/timeit.py
index 6c3ec01067f..9dfd454936e 100755
--- a/Lib/timeit.py
+++ b/Lib/timeit.py
@@ -72,6 +72,7 @@ def inner(_it, _timer{init}):
     _t0 = _timer()
     for _i in _it:
         {stmt}
+        pass
     _t1 = _timer()
     return _t1 - _t0
 """
diff --git a/Misc/NEWS.d/next/Library/2020-09-22-14-55-34.bpo-40670.R5sm68.rst b/Misc/NEWS.d/next/Library/2020-09-22-14-55-34.bpo-40670.R5sm68.rst
new file mode 100644
index 00000000000..0436194d736
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-09-22-14-55-34.bpo-40670.R5sm68.rst
@@ -0,0 +1,3 @@
+More reliable validation of statements in :class:`timeit.Timer`. It now
+accepts "empty" statements (only whitespaces and comments) and rejects
+misindentent statements.