Allow doctest to find line number of __test__ strings if formatted as a triple quoted string.

[bitdancer]

BPO	24925
Nosy	@jneb, @bitdancer, @jayvdb, @CuriousLearner, @nasirhjafri
PRs	bpo-24925: _find_lineno now finds doctest __test__ string line numbers #17553
Files	doctest_find__test__.patch doctestfix.py: Simple addition for doctest

^{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/CuriousLearner'
closed_at = None
created_at = <Date 2015-08-24.16:20:04.640>
labels = ['easy', '3.8', 'type-bug', '3.7']
title = 'Allow doctest to find line number of __test__ strings if formatted as a triple quoted string.'
updated_at = <Date 2019-12-31.13:04:09.450>
user = 'https://github.com/bitdancer'

bugs.python.org fields:

activity = <Date 2019-12-31.13:04:09.450>
actor = 'jneb'
assignee = 'CuriousLearner'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2015-08-24.16:20:04.640>
creator = 'r.david.murray'
dependencies = []
files = ['40242', '47482']
hgrepos = []
issue_num = 24925
keywords = ['patch', 'easy']
message_count = 12.0
messages = ['249060', '253317', '253319', '313757', '313758', '314454', '330253', '330460', '334200', '334211', '358193', '359114']
nosy_count = 5.0
nosy_names = ['jneb', 'r.david.murray', 'jayvdb', 'CuriousLearner', 'nasirhjafri']
pr_nums = ['17553']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue24925'
versions = ['Python 3.4', 'Python 3.5', 'Python 3.6', 'Python 3.7', 'Python 3.8']

Linked PRs

• gh-69113: Fix doctest to report line numbers for __test__ strings #141624

[bitdancer]

Attached is a patch that enhances doctest discovery so that it can correctly report the line number for doctest errors in tests that are string values of the __test__ dictionary. It only works if the strings are formatted as triple quoted strings, but since that is the most common case I think it is worth doing.

I don't have a test for this...I think it will require a unit test rather than adding to the doctests, since it needs to check the reported line number and other changes to test_doctest.py would change the line numbers.

[jneb]

I am not as good in making nice patches, but that code can be improved upon a bit as follows:
<insert patch intro blurb here, same as original>

+ if isinstance(obj, str) and source_lines is not None:
+ # This will find __test__ string doctests if and only if the string
+ # contains any unique line.
+ for offset,line in enumerate(obj.splitlines(keepends=True):
+ if source_lines.count(line)==1:
+ lineno = source_lines.index(line)-offset
+ break

         # We couldn't find the line number.
         return None

I thing this will improve legibility and probably also speed under most circumstances.

[jneb]

Oops. Lousy editing, I should have used return instead of break.

These 6 lines can be inserted in lib/doctest at line 1100:
+ if isinstance(obj, str) and source_lines is not None:
+ # This will find __test__ string doctests if and only if the string
+ # contains any unique line.
+ for offset,line in enumerate(obj.splitlines(keepends=True):
+ if source_lines.count(line)==1:
+ return source_lines.index(line)-offset

And it works fine for me; the code is quite general and has predictable behaviour: any test string with a unique line in it will work.

[jneb]

I always use the following piece of code that can be trivially used to patch the source.
It basically looks for a using line in the test string and finds it in the source file. If there is a match, we know where we are. Otherwise it falls back to the "normal" way.

[jneb]

Oh wait, I already posted that so long ago I forgot about it.
Oops.
Sorry about the repetition, folks.

• Jurjen

[CuriousLearner]

Hey Jurjen,

Do you mind converting your patch in a Pull request please?

[CuriousLearner]

Hey R. David Murray,

Where do you think the unit test for doctest should be placed?

Should it be in test_doctest.py?

[bitdancer]

Without looking at doctest.py, yes. I believe the doctests in that file should be already plugged in to the unittest framework, so adding new testcase containing a non-doctest unit test should work fine.

[nasirhjafri]

Hi, Should I convert patch into PR?
Thanks

[jneb]

Yes. That would make me happy. In the meantime I learned how to use git, so maybe I'll do the pull request myself next time. Thanks for the work.