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:

quoted

From: Derrick Stolee <redacted>

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.

quoted

Helped-by: Jeff King [off-list ref]
Helped-by: Johannes Schindelin [off-list ref]
Helped-by: Szeder Gábor [off-list ref]
Signed-off-by: Derrick Stolee <redacted>
---
 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!

 

quoted

+		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