Correct stacklevel of warnings when compile regular expressions

[serhiy-storchaka]

BPO	30375
Nosy	@ezio-melotti, @serhiy-storchaka
PRs	bpo-30375: Correct the stacklevel of regex compiling warnings. #1595 [3.6] bpo-30375: Correct the stacklevel of regex compiling warnings. (GH-1595) #1604 [3.5] bpo-30375: Correct the stacklevel of regex compiling warnings. (GH-1595) #1605 [2.7] bpo-30375: Correct the stacklevel of regex compiling warnings. (#1595) #1648

^{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 = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2017-05-18.10:46:58.638>
created_at = <Date 2017-05-15.19:47:50.166>
labels = ['expert-regex', 'type-bug', 'library', '3.7']
title = 'Correct stacklevel of warnings when compile regular expressions'
updated_at = <Date 2017-05-18.10:46:58.637>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2017-05-18.10:46:58.637>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2017-05-18.10:46:58.638>
closer = 'serhiy.storchaka'
components = ['Library (Lib)', 'Regular Expressions']
creation = <Date 2017-05-15.19:47:50.166>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 30375
keywords = []
message_count = 5.0
messages = ['293736', '293758', '293768', '293769', '293918']
nosy_count = 3.0
nosy_names = ['ezio.melotti', 'mrabarnett', 'serhiy.storchaka']
pr_nums = ['1595', '1604', '1605', '1648']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue30375'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6', 'Python 3.7']

[serhiy-storchaka]

When compile a regular expression with groups or conditionals emitted warnings point on lines in the re module implementation rather than the line in user code.

>>> import re
>>> re.compile('x(?i)')
__main__:1: DeprecationWarning: Flags not at the start of the expression x(?i)
re.compile('x(?i)', re.IGNORECASE)
>>> re.compile('(x(?i))')
/home/serhiy/py/cpython/Lib/re.py:281: DeprecationWarning: Flags not at the start of the expression (x(?i))
  p = sre_compile.compile(pattern, flags)
re.compile('(x(?i))', re.IGNORECASE)
>>> re.compile('((x(?i)))')
/home/serhiy/py/cpython/Lib/sre_parse.py:889: DeprecationWarning: Flags not at the start of the expression ((x(?i)))
  p = _parse_sub(source, pattern, flags & SRE_FLAG_VERBOSE, False)
re.compile('((x(?i)))', re.IGNORECASE)

Proposed patch fixes this:

>>> import re
>>> re.compile('x(?i)')
__main__:1: DeprecationWarning: Flags not at the start of the expression x(?i)
re.compile('x(?i)', re.IGNORECASE)
>>> re.compile('(x(?i))')
__main__:1: DeprecationWarning: Flags not at the start of the expression (x(?i))
re.compile('(x(?i))', re.IGNORECASE)
>>> re.compile('((x(?i)))')
__main__:1: DeprecationWarning: Flags not at the start of the expression ((x(?i)))
re.compile('((x(?i)))', re.IGNORECASE)

[serhiy-storchaka]

New changeset c7ac728 by Serhiy Storchaka in branch 'master':
bpo-30375: Correct the stacklevel of regex compiling warnings. (bpo-1595)
c7ac728

[serhiy-storchaka]

New changeset 73fb45d by Serhiy Storchaka in branch '3.6':
[3.6] bpo-30375: Correct the stacklevel of regex compiling warnings. (GH-1595) (bpo-1604)
73fb45d

[serhiy-storchaka]

New changeset 24b5ed2 by Serhiy Storchaka in branch '3.5':
[3.5] bpo-30375: Correct the stacklevel of regex compiling warnings. (GH-1595) (bpo-1605)
24b5ed2

[serhiy-storchaka]

New changeset dfcfc91 by Serhiy Storchaka in branch '2.7':
[2.7] bpo-30375: Correct the stacklevel of regex compiling warnings. (bpo-1595) (bpo-1648)
dfcfc91