Argument Clinic: inline parsing code for 1-argument functions

[serhiy-storchaka]

BPO	23867
Nosy	@vstinner, @larryhastings, @serhiy-storchaka, @ammaraskar, @tirkarthi
PRs	bpo-23867: Argument Clinic: inline parsing code for a single positional parameter. #9689
Dependencies	bpo-26305: Make Argument Clinic to generate PEP 7 conforming code bpo-26902: Argument Clinic incorrectly works with custom converter and renamed parameter
Files	clinic_meth_o_inline.patch clinic_meth_o_inline.patch

^{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 2018-12-25.14:57:41.640>
created_at = <Date 2015-04-04.14:24:36.243>
labels = ['type-feature', '3.8', 'expert-argument-clinic']
title = 'Argument Clinic: inline parsing code for 1-argument functions'
updated_at = <Date 2019-01-04.13:52:43.874>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2019-01-04.13:52:43.874>
actor = 'vstinner'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2018-12-25.14:57:41.640>
closer = 'serhiy.storchaka'
components = ['Argument Clinic']
creation = <Date 2015-04-04.14:24:36.243>
creator = 'serhiy.storchaka'
dependencies = ['26305', '26902']
files = ['38830', '42672']
hgrepos = []
issue_num = 23867
keywords = ['patch']
message_count = 10.0
messages = ['240074', '264596', '264629', '264631', '286788', '326979', '327493', '332507', '332511', '332978']
nosy_count = 5.0
nosy_names = ['vstinner', 'larry', 'serhiy.storchaka', 'ammar2', 'xtreak']
pr_nums = ['9689']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue23867'
versions = ['Python 3.8']

[serhiy-storchaka]

Proposed patch makes Argument Clinic to inline parsing code for most popular formats in functions with single positional argument. This makes parsing faster.

[serhiy-storchaka]

Synchronized with tip.

[larryhastings]

Why is this dependent on bpo-26305?

[serhiy-storchaka]

Because new generated code contains "if" statements and braces (and PEP-7 requires even more braces than current patch adds). The patch for bpo-26305 allows to repeat braces only twice instead of 4 times.

[vstinner]

I like the idea since I just proposed something similar in the issue bpo-29419, but it seems like your change removes the function name from error messages which can become much more obscure.

Maybe we should wrap all exceptions into a new TypeError which contains at least the function name, or even the parameter name/position. I mean chained exception to keep the original exception which contains more information.

The best would be to have all information in a single error message, but it is likely to be much more complex to implement, especially if you want to support arbitrary converter function, not only simple formats like i". So I think that two chained exceptions is a reasonable compromise. What do you think?

If we succeed to get the function name and the parameter name or position, the error messages will be MUCH MORE better than currently! And Argument Clinic allows us to implement this feature.

[serhiy-storchaka]

Thank you all for your comments. Addressed all comments, fixed few other bugs, added support for more convertors. I think this patch is completed.

This is just a first step. Next steps are adding support of multiple positional-only parameters, optional groups, and finally keyword parameters.

[vstinner]

I'm a little bit sad that the PR doesn't add new tests :-(

[serhiy-storchaka]

New changeset 32d96a2 by Serhiy Storchaka in branch 'master':
bpo-23867: Argument Clinic: inline parsing code for a single positional parameter. (GH-9689)
32d96a2

[serhiy-storchaka]

See bpo-35582 for next step.

[vstinner]

Nice optimization! I wanted to implement it, but then I forgot.