inspect.getframeinfo() cannot show first line

[sbt]

BPO	15812
Nosy	@pwaller, @berkerpeksag, @serhiy-storchaka
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	inspect_getframeinfo_line1.patch

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

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2017-01-02.03:59:36.628>
created_at = <Date 2012-08-29.14:54:39.228>
labels = ['3.7', 'type-bug', 'library']
title = 'inspect.getframeinfo() cannot show first line'
updated_at = <Date 2017-03-31.16:36:20.449>
user = 'https://bugs.python.org/sbt'

bugs.python.org fields:

activity = <Date 2017-03-31.16:36:20.449>
actor = 'dstufft'
assignee = 'none'
closed = True
closed_date = <Date 2017-01-02.03:59:36.628>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2012-08-29.14:54:39.228>
creator = 'sbt'
dependencies = []
files = ['27357']
hgrepos = []
issue_num = 15812
keywords = ['patch']
message_count = 11.0
messages = ['169387', '171638', '171640', '171641', '171643', '282427', '284452', '284453', '284471', '284516', '284517']
nosy_count = 6.0
nosy_names = ['Peter.Waller', 'python-dev', 'sbt', 'berker.peksag', 'serhiy.storchaka', 'Sam.Breese']
pr_nums = ['552']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue15812'
versions = ['Python 3.5', 'Python 3.6', 'Python 3.7']

[sbt]

When inspect.getframeinfo() tries to collect lines of context it never shows the first line (unless context is as big as the number of lines in the file).

The relevant code is

        start = lineno - 1 - context//2
        try:
            lines, lnum = findsource(frame)
        except IOError:
            lines = index = None
        else:
-->         start = max(start, 1)
            start = max(0, min(start, len(lines) - context))
            lines = lines[start:start+context]
            index = lineno - 1 - start

I think that

            start = max(start, 1)

should be replaced by

            start = max(start, 0)

For some reason getframeinfo() (and the functions which use it) don't seem to be tested by the testsuite...

[SamBreese]

Looking into this now. Should have a patch either later today or tommorow.

[SamBreese]

Also, would you mind posting an example? I'm having trouble replicating.

[SamBreese]

Nevermind, replicated it. Changing start = max(start, 1) to start = max(start, 0) DOES fix. Writing a test case now.

[SamBreese]

Here's a patch. Very, very simple, just changed that one line in inspect.py and wrote a highly primitive test case for inspect.getframeinfo. The test isn't actually testing the primary functionality right now, just this one bug. I can probably write more expansive coverage later, but in the interest of an expeditious reply I'm submitting now.

[pwaller]

I have just hit this bug and independently invented the exact fix of changing the zero for a one. Any chance of getting this merged?

[python-dev]

New changeset 15454cad5f27 by Berker Peksag in branch '3.5':
Issue bpo-15812: inspect.getframeinfo() now correctly shows the first line of a context
https://hg.python.org/cpython/rev/15454cad5f27

New changeset 410caf255a09 by Berker Peksag in branch '3.6':
Issue bpo-15812: Merge from 3.5
https://hg.python.org/cpython/rev/410caf255a09

New changeset 803c3c21c3bc by Berker Peksag in branch 'default':
Issue bpo-15812: Merge from 3.6
https://hg.python.org/cpython/rev/803c3c21c3bc

[berkerpeksag]

Thanks for the patch Sam and thanks for the ping Peter!

[serhiy-storchaka]

start is bounded to 0 twice.

    start = max(start, 0)
    start = max(0, min(start, len(lines) - context))

The first line can be just removed. Or two above lines can be rewritten as:

    start = min(start, len(lines) - context)
    start = max(start, 0)

[python-dev]

New changeset 2b6bdd6cd3f8 by Berker Peksag in branch '3.5':
Issue bpo-15812: Delete redundant max(start, 0)
https://hg.python.org/cpython/rev/2b6bdd6cd3f8

New changeset 7cbcee0c53e3 by Berker Peksag in branch '3.6':
Issue bpo-15812: Merge from 3.5
https://hg.python.org/cpython/rev/7cbcee0c53e3

New changeset 5b0dee884b0b by Berker Peksag in branch 'default':
Issue bpo-15812: Merge from 3.6
https://hg.python.org/cpython/rev/5b0dee884b0b

[berkerpeksag]

You're right. Thanks for the review, Serhiy!