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From: Derrick Stolee <stolee@gmail.com>
To: "SZEDER Gábor" <szeder.dev@gmail.com>,
	"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, johannes.schindelin@gmx.de, peff@peff.net,
	Derrick Stolee <dstolee@microsoft.com>,
	Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH v2 1/2] t5510-fetch.sh: demonstrate fetch.writeCommitGraph bug
Date: Wed, 23 Oct 2019 16:46:42 -0400	[thread overview]
Message-ID: <a9ba6007-aeb9-96b4-9436-8e956798be59@gmail.com> (raw)
In-Reply-To: <20191023141813.GA26017@szeder.dev>

On 10/23/2019 10:18 AM, SZEDER Gábor wrote:
> On Wed, Oct 23, 2019 at 01:01:34PM +0000, Derrick Stolee via GitGitGadget wrote:
>> From: Derrick Stolee <dstolee@microsoft.com>
>>
>> While dogfooding, Johannes found a bug in the fetch.writeCommitGraph
>> config behavior. His example initially happened during a clone with
>> --recurse-submodules, we found that this happens with the first fetch
>> after cloning a repository that contains a submodule:
>>
>> 	$ git clone <url> test
>> 	$ cd test
>> 	$ git -c fetch.writeCommitGraph=true fetch origin
>> 	Computing commit graph generation numbers: 100% (12/12), done.
>> 	BUG: commit-graph.c:886: missing parent <hash1> for commit <hash2>
>> 	Aborted (core dumped)
>>
>> In the repo I had cloned, there were really 60 commits to scan, but
>> only 12 were in the list to write when calling
>> compute_generation_numbers(). A commit in the list expects to see a
>> parent, but that parent is not in the list.
>>
>> A follow-up will fix the bug, but first we create a test that
>> demonstrates the problem.
>>
>> I used "test_expect_failure" for the entire test instead of
>> "test_must_fail" only on the command that I expect to fail. This is
>> because the BUG() returns an exit code so test_must_fail complains.
> 
> I don't think this paragraph is necessary; using 'test_expect_failure'
> is the way to demonstrate a known breakage.
> 
> 'test_must_fail' should only be used when the failure is the desired
> behavior of a git command.  (I used the word "desired" here, because
> you just used the word "expect" above in the sense that "I expect it
> to fail, because I know it's buggy, and I want to demonstrate that
> bug")

I guess that I prefer pointing out which line of the test fails, and
making that part of the test (that must otherwise pass). However, you
are right that test_expect_failure does a good job of communicating that
the test script shows an existing bug. Those are not always cleaned up
immediately, but at least we can find them easily.

>> Helped-by: Jeff King <peff@peff.net>
>> Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
>> Helped-by: Szeder Gábor <szeder.dev@gmail.com>
>> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
>> ---
>>  t/t5510-fetch.sh | 17 +++++++++++++++++
>>  1 file changed, 17 insertions(+)
>>
>> diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
>> index ecabbe1616..e8ae3af0b6 100755
>> --- a/t/t5510-fetch.sh
>> +++ b/t/t5510-fetch.sh
>> @@ -583,6 +583,23 @@ test_expect_success 'fetch.writeCommitGraph' '
>>  	)
>>  '
>>  
>> +test_expect_failure 'fetch.writeCommitGraph with submodules' '
>> +	pwd="$(pwd)" &&
>> +	git clone dups super &&
>> +	(
>> +		cd super &&
>> +		git submodule add "file://$pwd/three" &&
> 
> Nits: couldn't the URL simply be file://$TRASH_DIRECTORY/three ?

True, that would be better. Thanks!

 
>> +		git commit -m "add submodule"
>> +	) &&
>> +	git clone "super" writeError &&
> 
> There is a write error now, because we have a bug, but after the next
> patch the bug will be fixed and we won't have a write error anymore.

Good point.

Thanks!
-Stolee

  reply	other threads:[~2019-10-23 20:46 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-22 17:28 [PATCH 0/1] [v2.24.0-rc0 BUG] fetch.writeCommitGraph fails on first fetch Derrick Stolee via GitGitGadget
2019-10-22 17:28 ` [PATCH 1/1] commit-graph: fix writing first commit-graph during fetch Derrick Stolee via GitGitGadget
2019-10-22 20:33   ` Jeff King
2019-10-22 21:45     ` Jeff King
2019-10-22 23:35       ` SZEDER Gábor
2019-10-23  0:35         ` Derrick Stolee
2019-10-23  0:48           ` Jeff King
2019-10-23  1:22             ` Jeff King
2019-10-23 13:01 ` [PATCH v2 0/2] [v2.24.0-rc0 BUG] fetch.writeCommitGraph fails on first fetch Derrick Stolee via GitGitGadget
2019-10-23 13:01   ` [PATCH v2 1/2] t5510-fetch.sh: demonstrate fetch.writeCommitGraph bug Derrick Stolee via GitGitGadget
2019-10-23 14:18     ` SZEDER Gábor
2019-10-23 20:46       ` Derrick Stolee [this message]
2019-10-24 12:18     ` SZEDER Gábor
2019-10-23 13:01   ` [PATCH v2 2/2] commit-graph: fix writing first commit-graph during fetch Derrick Stolee via GitGitGadget
2019-10-23 15:04     ` SZEDER Gábor
2019-10-24 10:39       ` Derrick Stolee
2019-10-30 14:31         ` SZEDER Gábor
2019-10-24 12:18   ` [PATCH v3 0/2] [v2.24.0-rc0 BUG] fetch.writeCommitGraph fails on first fetch Derrick Stolee via GitGitGadget
2019-10-24 12:18     ` [PATCH v3 1/2] t5510-fetch.sh: demonstrate fetch.writeCommitGraph bug Derrick Stolee via GitGitGadget
2019-10-24 12:18     ` [PATCH v3 2/2] commit-graph: fix writing first commit-graph during fetch Derrick Stolee via GitGitGadget
2019-10-24 13:40     ` [PATCH v4 0/2] [v2.24.0-rc0 BUG] fetch.writeCommitGraph fails on first fetch Derrick Stolee via GitGitGadget
2019-10-24 13:40       ` [PATCH v4 1/2] t5510-fetch.sh: demonstrate fetch.writeCommitGraph bug Derrick Stolee via GitGitGadget
2019-10-24 13:40       ` [PATCH v4 2/2] commit-graph: fix writing first commit-graph during fetch Derrick Stolee via GitGitGadget

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