[llvm-dev] Python 2 compatibility for utility scripts

[Nico Weber via llvm-dev]

How do you define "non-critical"? That seems like a rule that's hard to
apply consistently.

In this case, they're covered by tests, so they're considered somewhat
critical I suppose.

I personally have no problem if we make the decision to drop Py 2 support
across the board, but allowing a mix seems confusing to me.

If we do want to drop Py 2 support, we should probably use the same process
we use for bumping C++ or CMake versions: List advantages and costs, and
evaluate based on that. Since Py 2 is still the only installed Python on
fairly recent OS versions, I weakly feel that dropping support for it is
premature, but I don't care all that much. I do care that the community has
a "yes" or "no" answer to the question "do we support Python 2?".

On Tue, Dec 17, 2019 at 9:18 AM James Y Knight <jyknight at google.com> wrote:

> IMO, having non-critical utility scripts require python 3 should be
> allowed now. But, not yet for any scripts which are critical to build or
> test the distributed components.
>
> If we need to spend some time to fix the test runner to allow properly
> skipping tests of python3-only components when python3 isn't available,
> that seems entirely worthwhile, since we only need to do that once.
>
>
>
> On Tue, Dec 17, 2019, 7:43 AM Nico Weber via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> On Tue, Dec 17, 2019 at 5:12 AM Serge Guelton <sguelton at redhat.com>
>> wrote:
>>
>>> At the beginning of the year, I've landed a large set of patches to
>>> support both Python 2 and Python3 in most Python scripts. Looks like I
>>> missed some of them :-)
>>> At that time, backward portability with Python2 was still relevant, and
>>> I suspect it will still be the case for a few distributions that ship
>>> Python2 by default. That being said, Even RHEL8 uses Python3 by default, so
>>> at some point we may be able to drop the compatibility stuff.
>>> Until then, I'd argue for maintaining compatibility as it's not a
>>> tremendous task.
>>>
>>
>> This is my feeling as well. In yesterday's instance, I lost more time to
>> fixing bugs in the py3 detection logic on systems that don't have it than
>> it took me to make the script just run fine with both Python 2 and 3.
>>
>> On macOS, I think 10.15 is the first version that ships with python3, and
>> that was released just 2 months ago.
>>
>>
>>>
>>> On Tue, Dec 17, 2019 at 10:54 AM James Henderson via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> I personally only use Python 3 reluctantly. I've yet to encounter a
>>>> situation where I actually preferred Python 3. That being said, given the
>>>> decision to retire Python 2.7 (*grumble* *grumble*), I'll probably be
>>>> forced sometime in the new year to uninstall it by somebody in charge of
>>>> security somewhere. I certainly don't see a personal need to have all
>>>> scripts support Python 2, unless they are used in the build/test pipeline
>>>> somewhere (i.e. get touched by a fresh check-all).
>>>>
>>>> On Tue, 17 Dec 2019 at 05:31, Fangrui Song via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>
>>>>> https://reviews.llvm.org/D71565 intends to update
>>>>> llvm/utils/update_cc_test_checks.py to work with Python 2.
>>>>>
>>>>> In the original review, I suggested that we don't add Python 2
>>>>> compatibility for new features because Python 2.7 is retiring and some
>>>>> Linux distributions are even deprecating/removing Python 2 support. My
>>>>> feeling is:
>>>>>
>>>>> If some utilities do not support Python 2, we should probably not
>>>>> bother
>>>>> making them Python 2 compatible. Maintaining Python 2/3 compatibility
>>>>> may not worth the efforts. "utilities" include some command line tools
>>>>> under llvm/utils, which are not part of instructure like lit. What do
>>>>> people think?
>>>>>
>>>>> BTW, what's the Python 3 support status of build bots? Are there any
>>>>> running Python 3?
>>>>> _______________________________________________
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>>>>> llvm-dev at lists.llvm.org
>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>
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>
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