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Re: [PATCH v2 27/29] pack-objects: fix buggy warning about threads




On Mon, May 15, 2017 at 10:59 AM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> Ævar Arnfjörð Bjarmason  <avarab@xxxxxxxxx> writes:
>
>> Fix a buggy warning about threads under NO_PTHREADS=YesPlease. Due to
>> re-using the delta_search_threads variable for both the state of the
>> "pack.threads" config & the --threads option, setting "pack.threads"
>> but not supplying --threads would trigger the warning for both
>> "pack.threads" & --threads.
>>
>> Solve this bug by resetting the delta_search_threads variable in
>> git_pack_config(), it might then be set by --threads again and be
>> subsequently warned about, as the test I'm changing here asserts.
>>
>> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
>> ---
>>  builtin/pack-objects.c | 4 +++-
>>  t/t5300-pack-object.sh | 3 +--
>>  2 files changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
>> index 0fe35d1b5a..f1baf05dfe 100644
>> --- a/builtin/pack-objects.c
>> +++ b/builtin/pack-objects.c
>> @@ -2472,8 +2472,10 @@ static int git_pack_config(const char *k, const char *v, void *cb)
>>                       die("invalid number of threads specified (%d)",
>>                           delta_search_threads);
>>  #ifdef NO_PTHREADS
>> -             if (delta_search_threads != 1)
>> +             if (delta_search_threads != 1) {
>>                       warning("no threads support, ignoring %s", k);
>> +                     delta_search_threads = 0;
>> +             }
>>  #endif
>>               return 0;
>>       }
>> diff --git a/t/t5300-pack-object.sh b/t/t5300-pack-object.sh
>> index 1629fa80b0..0ec25c4966 100755
>> --- a/t/t5300-pack-object.sh
>> +++ b/t/t5300-pack-object.sh
>> @@ -445,8 +445,7 @@ test_expect_success !PTHREADS,C_LOCALE_OUTPUT 'pack-objects --threads=N or pack.
>>       git -c pack.threads=2 pack-objects --stdout --all </dev/null >/dev/null 2>err &&
>>       cat err &&
>>       grep ^warning: err >warnings &&
>> -     test_line_count = 2 warnings &&
>> -     grep -F "no threads support, ignoring --threads" err &&
>> +     test_line_count = 1 warnings &&
>>       grep -F "no threads support, ignoring pack.threads" err &&
>>       git -c pack.threads=2 pack-objects --threads=4 --stdout --all </dev/null >/dev/null 2>err &&
>>       grep ^warning: err >warnings &&
>
> Commenting on both 26 and 27.
>
> The usual way we document a known breakage to be fixed is to write a
> test that checks for the desired outcome with test_expect_failure,
> and when a patch corrects the behaviour we just flip it to expect
> success instead.  On the other hand, when we document a behaviour
> that is accepted/acceptable we would have a test that checks for the
> then-accepted behaviour with test_expect_success, and a patch that
> improves the behaviour would update the expectation.
>
> This follows the second pattern, even though the log message for the
> patches claim this is about an existing bug and its fix.
>
> Now, I am not saying (at least not yet) that 26 & 27 violates the
> established practice and they must be changed to expect seeing only
> one line of output in warnings with test_expect_failure in patch 26
> which is flipped to test_expect_success in patch 27.  Yes, it does
> not follow the usual pattern, but it gives a good food-for-thought.
>
> Perhaps our usual pattern may be suboptimal in illustrating in what
> way the current behaviour is not desirable, and the way these two
> patches document the current breakage and then documents the fixed
> behaviour may be a better example to follow?  With our usual way, it
> is not apparent until you actually run the tests with the current
> code what the questionable current behaviour is, but with the way
> patch 26 is written, we can tell that two warnings are given,
> instead of one.
>
> I dunno.  What do others think?

I think it makes sense to make use of test_expect_failure here. I'll
do that in v3.