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bpo-38956: don't print BooleanOptionalAction's default twice #27672

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merged 4 commits into from Aug 16, 2021
Merged

bpo-38956: don't print BooleanOptionalAction's default twice #27672

merged 4 commits into from Aug 16, 2021

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@mhils
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@mhils mhils commented Aug 9, 2021 •
edited by bedevere-bot

This PR is a less intrusive fix to not double-print the default value when using argparse.BooleanOptionalAction with ArgumentDefaultsHelpFormatter. The original bug report (bpo-38956) was about removing the default entirely, but @rhettinger made a sensible point in #17447 (comment) that a default should always been shown here. While #17447 seems to work as intended, progress stalled a bit presumably because it's not entirely trivial to review. This PR proposes a more straightforward attempt to solve the problem, which can hopefully be reviewed more easily. If the maintainers ultimately prefers #17447 that is perfectly fine with me of course. 😃

In short, in this PR we make use of the fact that ArgumentDefaultsHelpFormatter already checks if the default is already included:

cpython/Lib/argparse.py

Line 693 in 2b496e7

if '%(default)' not in action.help:

This condition previously did not trigger because BooleanOptionalAction already did the string interpolation directly.

https://bugs.python.org/issue38956
@mhils mhils force-pushed the show-default branch from 884f08f to 94a32b8 Aug 9, 2021
@ambv ambv mentioned this pull request Aug 16, 2021
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@ambv ambv commented Aug 16, 2021

Confirmed that the test fails without the source change:

-   --taz, --no-taz  Whether to taz it (default: True)
+   --taz, --no-taz  Whether to taz it (default: True) (default: True)
?                                                ++++++++++++++++
    --quux QUUX      Set the quux (default: 42)

(that diffing algorithm is weird)

@ambv ambv merged commit 1512bc2 into python:main Aug 16, 2021
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@miss-islington
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@miss-islington miss-islington commented Aug 16, 2021

Thanks @mhils for the PR, and @ambv for merging it 🌮🎉.. I'm working now to backport this PR to: 3.9, 3.10.
🐍🍒⛄1�7🤖

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@miss-islington miss-islington commented Aug 16, 2021

Sorry, @mhils and @ambv, I could not cleanly backport this to 3.9 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 1512bc21d60f098a9e9f37b44a2f6a9b49a3fd4f 3.9

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@bedevere-bot bedevere-bot commented Aug 16, 2021

GH-27787 is a backport of this pull request to the 3.10 branch.

miss-islington added a commit to miss-islington/cpython that referenced this issue Aug 16, 2021
@mhils @miss-islington
bpo-38956: don't print BooleanOptionalAction's default twice (pythonG 1�7
e2920b1 
…H-27672)

Co-authored-by: Micky Yun Chan <michan@redhat.com>
(cherry picked from commit 1512bc2)

Co-authored-by: Maximilian Hils <git@maximilianhils.com>
ambv added a commit to ambv/cpython that referenced this issue Aug 16, 2021
@mhils @ambv
[3.9] bpo-38956: don't print BooleanOptionalAction's default twice (p 1�7
403abbc 
…ythonGH-27672)

Co-authored-by: Micky Yun Chan <michan@redhat.com>.
(cherry picked from commit 1512bc2)

Co-authored-by: Maximilian Hils <git@maximilianhils.com>
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@bedevere-bot bedevere-bot commented Aug 16, 2021

GH-27788 is a backport of this pull request to the 3.9 branch.

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@abadger abadger commented Aug 16, 2021

Hi, I don't think this was the right fix for this issue (or maybe better stated as... this is an incomplete fix that leaves two diverging code paths which should be consolidated). Please see https://bugs.python.org/issue44587 for my explanation of what I think should be done (Option 2 if we want to go the nonintrusive route). I have an implementation of option 2 vendored into one of my projects here: ansible-community/antsibull@67f6d1a#diff-f515d1b9734c55a77e0a94b093b41eb1102a986be60631df39ac1513895aba07 I can pull that out into a pr but I had been waiting on someone to confirm that Option 2 is really the desired outcome considering the architecture of argparse.

@mhils mhils deleted the show-default branch Aug 16, 2021
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@mhils mhils commented Aug 16, 2021 •
edited by bedevere-bot

Thanks @ambv! ❤️

@abadger: My intention with this PR was to unblock a somewhat stalled issue with changes that are trivial to review. bpo-44587 wasn't linked at bpo-38956 so I wasn't aware of it. The changes here shouldn't affect the usefulness of what you proposed, I'd suggest you go ahead and open a PR for your option 2. :)

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@abadger abadger commented Aug 17, 2021 •
edited by bedevere-bot

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@ambv ambv commented Aug 17, 2021

@abadger, this was merged because it's a rather trivial improvement over the status quo. I intend to also release this fix in 3.9.7 on August 30th. Your idea in BPO-44587 to further improve this while retaining displaying the default value is interesting. If you prepare a PR we can work with, we'll look into merging that as well.

ambv added a commit that referenced this issue Aug 17, 2021
@mhils @ambv
[3.9] bpo-38956: don't print BooleanOptionalAction's default twice (G 1�7
27fd313 
…H-27672) (GH-27788)

Co-authored-by: Micky Yun Chan <michan@redhat.com>.
(cherry picked from commit 1512bc2)

Co-authored-by: Maximilian Hils <git@maximilianhils.com>
miss-islington added a commit that referenced this issue Aug 17, 2021
@mhils @miss-islington
bpo-38956: don't print BooleanOptionalAction's default twice (GH-27672)
6f6648e 
Co-authored-by: Micky Yun Chan <michan@redhat.com>
(cherry picked from commit 1512bc2)

Co-authored-by: Maximilian Hils <git@maximilianhils.com>
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