Subject: Re: [PATCH v2 1/3] stash: add test to ensure reflog --rewrite --updatref behavior

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Fri, 25 Feb 2022 12:45:19 +0100

On Thu, Feb 24 2022, John Cai wrote:

> Hi Ævar,
>
> On 23 Feb 2022, at 16:50, Ævar Arnfjörð Bjarmason wrote:
>
>> On Wed, Feb 23 2022, Junio C Hamano wrote:
>>
>>> Ævar Arnfjörð Bjarmason <[email-masked]> writes:
>>>
>>>> This test was already a bit broken in needing the preceding tests, but
>>>> it will break now if REFFILES isn't true, which you can reproduce
>>>> e.g. with:
>>>>
>>>>     ./t3903-stash.sh --run=1-16,18-50 -vixd
>>>>
>>>> Perhaps the least sucky solution to that is:
>>>>
>>>> diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
>>>> index ec9cc5646d6..1d11c9bda20 100755
>>>> --- a/t/t3903-stash.sh
>>>> +++ b/t/t3903-stash.sh
>>>> @@ -205,13 +205,19 @@ test_expect_success 'drop stash reflog updates refs/stash with rewrite' '
>>>>  	cat >expect <<-EOF &&
>>>>  	$(test_oid zero) $oid
>>>>  	EOF
>>>> -	test_cmp expect actual
>>>> +	test_cmp expect actual &&
>>>> +	>dropped-stash
>>>>  '
>>>
>>> If "git stash drop", invoked in earlier part of this test before the
>>> precontext, fails, then test_cmp would fail and we leave
>>> dropped-stash untouched, even though we did run "git stash drop"
>>> already.
>>
>> Yes, that's an edge case that's exposed here, but which I thought wasn't
>> worth bothering with. I.e. if you get such a failure on test N getting
>> N+1 failing as well isn't that big of a deal.
>>
>> The big deal is rather that we know we're adding a REFFILES dependency
>> to this, which won't run this at all, which will make the "stash pop"
>> below fail.
>>
>>> Why does the next test need to depend on what has happened earlier?
>>
>> They don't need to, and ideally wouldn't, but most of our test suite has
>> this issue already. Try e.g. running it with:
>>
>>     prove t[0-9]*.sh :: --run=10-20 --immediate
>>
>> And for this particular file running e.g. this on master:
>>
>>     ./t3903-stash.sh --run=1-10,30-40
>>
>> Will fail 7 tests in the 30-40 range.
>>
>> So while it's ideal that we can combine tests with arbitrary --run
>> parameters, i.e. all tests would tear down fully, not depend on earlier
>> tests etc. we're really far from that being the case in practice.
>>
>> So insisting on some general refactoring of this file as part of this
>> series seems a bit overzelous, which is why I'm suggesting the bare
>> minimum to expect and work around the inevitable REFFILES failure, as
>> Han-Wen is actively working in that area.
>
> Curious what your thoughts are on an effort to isolate these tests from each other.
> I like your approach in t/t1417 in creating a test repo and copying it over each time.
> Something like this?

That looks good to me if you're willing to do that legwork, probably
better in a preceding cleanup commit.

> diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
> index ac345eced8cb..40254f8dc99c 100755
> --- a/t/t3903-stash.sh
> +++ b/t/t3903-stash.sh
> @@ -41,7 +41,9 @@ diff_cmp () {
>         rm -f "$1.compare" "$2.compare"
>  }
>
> -test_expect_success 'stash some dirty working directory' '
> +test_expect_success 'setup' '
> +       git init repo &&
> +       cd repo &&
>         echo 1 >file &&
>         git add file &&
>         echo unrelated >other-file &&
> @@ -54,48 +56,54 @@ test_expect_success 'stash some dirty working directory' '
>         test_tick &&
>         git stash &&
>         git diff-files --quiet &&
> -       git diff-index --cached --quiet HEAD
> +       git diff-index --cached --quiet HEAD &&
> +       cat >expect <<-EOF &&

nit: you can add \ to that, i.e. <<-\EOF. Helps readability, i.e.  it's
obvious right away that no variables are in play..

> +       diff --git a/file b/file
> +       index 0cfbf08..00750ed 100644
> +       --- a/file
> +       +++ b/file
> +       @@ -1 +1 @@
> +       -2
> +       +3
> +       EOF
> +       cd ../
>  '
>
> -cat >expect <<EOF
> -diff --git a/file b/file
> -index 0cfbf08..00750ed 100644
> ---- a/file
> -+++ b/file
> -@@ -1 +1 @@
> --2
> -+3
> -EOF
> +test_stash () {
> +       cp -R repo copy &&
> +       cd copy &&
> +       test_expect_success "$@" &&
> +       cd ../ &&
> +       rm -rf copy
> +}
>
>
> -test_expect_success 'parents of stash' '
> +test_stash 'parents of stash' '
>         test $(git rev-parse stash^) = $(git rev-parse HEAD) &&
>         git diff stash^2..stash >output &&
>         diff_cmp expect output
>  '

For this sort of thing I think it's usually better to override
"test_expect_success" as a last resort, i.e. to have that
"test_setup_stash_copy" just be a "setup_stash" or whatever function
called from within your test_expect_success.

And instead of the "rm -rf" later, just do:

    test_when_finished "rm -rf copy" &&
    cp -R repo copy &&
    [...]

The test still needs to deal with the sub-repo, but it could cd or use
"-C".

It's bad to add "cd .." in a &&-chain, because if earlier steps fail
we're in the wrong directory for the next test, so either -C or a
sub-shell...

> Not sure if it's worth it though?

Maybe not, which is why I suggested upthread to maybe go for some
smallest possible change here and focus on the lib-ificitaion :)

>
>
>>
>>>>  test_expect_success 'stash pop' '
>>>>  	git reset --hard &&
>>>>  	git stash pop &&
>>>> -	test 9 = $(cat file) &&
>>>> +	if test -e dropped-stash
>>>> +	then
>>>> +		test 9 = $(cat file)
>>>> +	else
>>>> +		test 3 = $(cat file)
>>>> +	fi &&
>>>>  	test 1 = $(git show :file) &&
>>>>  	test 1 = $(git show HEAD:file) &&
>>>>  	test 0 = $(git stash list | wc -l)