trace module cli does not write cover files

[MichaelSelik]

BPO	31908
Nosy	@rhettinger, @abalkin, @berkerpeksag, @serhiy-storchaka, @selik, @ZackerySpytz, @miss-islington
PRs	bpo-31908: Fix output of cover files for trace module command-line tool #4205 [3.7] bpo-31908: Fix output of cover files for trace module command-line tool. (GH-4205) #6666 [3.6] bpo-31908: Fix output of cover files for trace module command-line tool. (GH-4205) #6667 [3.6] bpo-31908: Fix output of cover files for trace module command-line tool. (GH-4205) #6668 bpo-26818: Add a test to make sure the bug is fixed #8664 [3.7] bpo-26818: Add a test to make sure the bug is fixed (GH-8664) #8732

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-10-31.02:55:06.847>
labels = ['3.7', 'type-bug', 'library']
title = 'trace module cli does not write cover files'
updated_at = <Date 2018-08-11.06:28:37.697>
user = 'https://bugs.python.org/MichaelSelik'

bugs.python.org fields:

activity = <Date 2018-08-11.06:28:37.697>
actor = 'berker.peksag'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2017-10-31.02:55:06.847>
creator = 'Michael Selik'
dependencies = []
files = []
hgrepos = []
issue_num = 31908
keywords = ['patch']
message_count = 13.0
messages = ['305268', '305269', '305341', '305343', '305347', '305367', '306173', '315980', '315981', '315984', '323058', '323401', '323403']
nosy_count = 8.0
nosy_names = ['rhettinger', 'belopolsky', 'berker.peksag', 'serhiy.storchaka', 'selik', 'Michael Selik', 'ZackerySpytz', 'miss-islington']
pr_nums = ['4205', '6666', '6667', '6668', '8664', '8732']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue31908'
versions = ['Python 3.6', 'Python 3.7']

[MichaelSelik]

The trace module command-line utility doesn't write cover files. I've noticed this issue for some years now. It works fine in Python 2. When using Python 3, no ".cover" files are written, regardless of how "--coverdir" is specified.

mike on macbook in ~/
$ echo 'print("hello")' > foo.py

mike on macbook in ~/
$ python -m trace --count foo.py
hello

mike on macbook in ~/
$ ls *.cover
ls: *.cover: No such file or directory

My apologies if this is a duplicate bug. I searched the tracker and Google for a while, but couldn't find a relevant issue.

[rhettinger]

It worked in Python 3.4, but not afterwards.

[MichaelSelik]

The problem appears to be a mistake in commit f026dae

f026dae

This made the writing of cover files conditional on show_missing which is the option to mark lines which weren't executed with several angle brackets ">>>>>".

https://github.com/python/cpython/blob/3.5/Lib/trace.py#L326

mike on mac in ~/
$ python -m trace --count foo.py
hello

mike on mac in ~/
$ ls *.cover
ls: *.cover: No such file or directory

mike on mac in ~/
$ python -m trace --count -m foo.py
hello

mike on mac in ~/
$ ls *.cover
-rw-r--r--  1 mike  staff    22B Oct 31 15:40 foo.cover

[MichaelSelik]

While writing a patch for this, I noticed the lnotab parameter seems nearly unused. It's a dict, but is only used for its keys.

https://github.com/python/cpython/blob/master/Lib/trace.py#L333

Further, the choice to count unreached lines only when show_missing was set seems inconsistent.

https://github.com/python/cpython/blob/master/Lib/trace.py#L335

https://github.com/python/cpython/blob/master/Lib/trace.py#L280

[MichaelSelik]

Ok, pull request submitted:
#4205

[berkerpeksag]

I think the first part of your patch also fixes bpo-26818. Could you adapt the test there and add a test case for the problem in this issue?

[selik]

You're referring to something like this:

+ def test_count_and_summary(self):
+ name = TESTFN + '.py'
+ with open(name, 'w') as fd:
+ self.addCleanup(unlink, name)
+ fd.write("""\
+x = 1
+y = 2
+
+def f():
+ return x + y
+
+for i in range(10):
+ f()
+ """)
+ status, stdout, stderr = assert_python_ok('-m', 'trace', '-cs', name)
+ self.assertEqual(status, 0)
+ self.assertIn(b'lines cov% module (path)', stdout)
+ self.assertIn(('6 100%% %s (%s)' % (TESTFN, name)).encode(), stdout)
+

?

[serhiy-storchaka]

New changeset 47ab154 by Serhiy Storchaka (Michael Selik) in branch 'master':
bpo-31908: Fix output of cover files for trace module command-line tool. (GH-4205)
47ab154

[miss-islington]

New changeset e4eeb6e by Miss Islington (bot) in branch '3.7':
bpo-31908: Fix output of cover files for trace module command-line tool. (GH-4205)
e4eeb6e

[miss-islington]

New changeset a607f8b by Miss Islington (bot) in branch '3.6':
bpo-31908: Fix output of cover files for trace module command-line tool. (GH-4205)
a607f8b

[ZackerySpytz]

This change causes test_trace to leave a trace.cover file in the Lib directory (see bpo-34171).

[berkerpeksag]

New changeset c8b0dbc by Berker Peksag in branch 'master':
bpo-26818: Add a test to make sure the bug is fixed (GH-8664)
c8b0dbc