Subject: Re: [GSoC][PATCH v3 2/3] t0000: avoid using pipes

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Sun, 24 Mar 2019 20:04:34 +0100

On Sun, Mar 24 2019, jonathan chang wrote:

> On Mon, Mar 18, 2019 at 12:47 AM Ævar Arnfjörð Bjarmason
> <[email-masked]> wrote:
>>
>>
>> On Sun, Mar 17 2019, Jonathan Chang wrote:
>>
>> > The exit code of the upstream in a pipe is ignored thus we should avoid
>> > using it. By writing out the output of the git command to a file, we can
>> > test the exit codes of both the commands.
>> >
>> > Signed-off-by: Jonathan Chang <[email-masked]>
>> > ---
>> >  t/t0000-basic.sh | 28 ++++++++++++++--------------
>> >  1 file changed, 14 insertions(+), 14 deletions(-)
>> >
>> > diff --git a/t/t0000-basic.sh b/t/t0000-basic.sh
>> > index 53821f5817..47666b013e 100755
>> > --- a/t/t0000-basic.sh
>> > +++ b/t/t0000-basic.sh
>> > @@ -1118,27 +1118,25 @@ P=$(test_oid root)
>> >
>> >  test_expect_success 'git commit-tree records the correct tree in a commit' '
>> >       commit0=$(echo NO | git commit-tree $P) &&
>> > -     tree=$(git show --pretty=raw $commit0 |
>> > -              sed -n -e "s/^tree //p" -e "/^author /q") &&
>> > +     git show --pretty=raw $commit0 >actual &&
>> > +     tree=$(sed -n -e "s/^tree //p" -e "/^author /q" actual) &&
>> >       test "z$tree" = "z$P"
>>
>> This change is an improvement just changing the "git" invocations. But I
>> wonder as we're reviewing this / churning this if we couldn't also
>> modernize this style to just:
>>
>>     git .. >tmp &&
>>     sed -n -e <tmp >actual &&
>>     test_must_be_empty actual
>
> Do you mean something like this:
>
> -       git show --pretty=raw $commit0 >actual &&
> -       tree=$(sed -n -e "s/^tree //p" -e "/^author /q" actual) &&
> -       test "z$tree" = "z$P"
> +       git show --pretty=raw $commit0 >tmp &&
> +       sed -n -e "/$P/d" -e "s/^tree //p" -e "/^author /q" tmp >actual &&
> +       test_must_be_empty actual
>
> It works. But the semantic is different if we use test_must_be_empty.
> I wonder if you mean test_cmp because I found some commits[1 2 3]
> that changes 'test "z...' to use test_cmp with 'git log -G 'test "z' --oneline'
> and git-show. However, they are all around 2013, so I'm not so sure
> this is what you mean either.
>
> I did found some use of sed's 'd' function in conjunction with
> test_must_be_empty, using:
>   git grep -A 5 'sed .*/d' | grep -B 5 'test_must_be_empty'
> However, they don't use parameter expansion in sed.
>
> There are some places where parameter expansion is used in sed, but
> that would require test_cmp in this case, and would need to write to
> another file to compare.
>
> Maybe this 'test "z$A" = "z$B"' syntax is fine, yet most of the existing
> usages are added around 12 years ago according git-blame I saw on
> github.
>
>
> [1]: 03c893cbf9 ("t1006: modernize output comparisons", 2013-07-10)
> [2]: 848575d833 ("push test: simplify check of push result", 2013-03-18)
> [3]: ed838e6615 ("t1300: style updates", 2012-10-23)

Yeah there's many ways to do it. Generally we've been moving to the
"test_*" wrapper that e.g. given X lines print out an explanation that
we were expecting Y instead.

>> > @@ -1162,12 +1161,13 @@ test_expect_success 'very long name in the index handled sanely' '
>> >       >path4 &&
>> >       git update-index --add path4 &&
>> >       (
>> > -             git ls-files -s path4 |
>> > -             sed -e "s/      .*/     /" |
>> > +             git ls-files -s path4 >actual &&
>> > +             sed -e "s/      .*/     /" actual |
>> >               tr -d "\012" &&
>> >               echo "$a"
>> >       ) | git update-index --index-info &&
>> > -     len=$(git ls-files "a*" | wc -c) &&
>> > +     git ls-files "a*" >actual &&
>> > +     len=$(wc -c <actual) &&
>> >       test $len = 4098
>>
>> Ditto. Maybe the initial author wanted to avoid writing out 4k lines,
>> but now that we're doing so anyway...
>
> This is 'wc -c', so I think I don't have to modify it?

Yes, that's a brainfart of mine. Although as an aside I have a WIP
series that adds test_byte_count which can be used for these types of
cases.

> By the way, I found 2 lines that can be changed to use test_must_be_empty
> in t0000-basic.sh. I paste the diff below:
> ---
> @@ -51,7 +51,7 @@ test_expect_success 'verify that the running shell
> supports "local"' '
>
>  test_expect_success '.git/objects should be empty after git init in
> an empty repo' '
>         find .git/objects -type f -print >should-be-empty &&
> -       test_line_count = 0 should-be-empty
> +       test_must_be_empty should-be-empty
>  '
>
>  # also it should have 2 subdirectories; no fan-out anymore, pack, and info.
> @@ -1110,7 +1110,7 @@ test_expect_success 'git update-index --refresh
> should succeed' '
>
>  test_expect_success 'no diff after checkout and git update-index --refresh' '
>         git diff-files >current &&
> -       cmp -s current /dev/null
> +       test_must_be_empty current
>  '