Assertion failure with git cat-file --batch-command

I unexpectedly managed to hit this:
git: builtin/cat-file.c:387: print_object_or_die: Assertion
`data->info.typep' failed.
Aborted (core dumped)

(That's in print_object_or_die().)

Here's the bugreport.

Thank you for filling out a Git bug report!
Please answer the following questions to help us understand your issue.

What did you do before the bug happened? (Steps to reproduce your issue)

~$ mkdir foo
~$ cd foo
~/foo$ git init
Initialized empty Git repository in /home/alan/foo/.git/
~/foo (main)$ echo hello > hello
~/foo (main)$ git add hello
~/foo (main)$ git commit -m"first"
[main (root-commit) d62fc70] first
 1 file changed, 1 insertion(+)
 create mode 100644 hello
~/foo (main)$ git ls-tree HEAD
100644 blob ce013625030ba8dba906f756967f9e9ca394464a hello
~/foo (main)$ echo ce013625030ba8dba906f756967f9e9ca394464a | git
cat-file --batch="%(objectsize)"
6
hello

~/foo (main)$ echo info ce013625030ba8dba906f756967f9e9ca394464a | git
cat-file --batch-command="%(objectsize)"
6
~/foo (main)$ echo contents ce013625030ba8dba906f756967f9e9ca394464a |
git cat-file --batch-command="%(objecttype) %(objectsize)"
blob 6
hello

~/foo (main)$ echo contents ce013625030ba8dba906f756967f9e9ca394464a |
git cat-file --batch-command="%(objectsize)"
6
git: builtin/cat-file.c:387: print_object_or_die: Assertion
`data->info.typep' failed.
Aborted (core dumped)

What did you expect to happen? (Expected behavior)

cat-file prints the size of the blob and then the blob contents

What happened instead? (Actual behavior)

Assertion failure, core dump

What's different between what you expected and what actually happened?

The abort

Anything else you want to add:

I first observed this in 2.43.0, but it still seems to be present in
2.54.0.

Note that if I ask git cat-file --batch-command to include the
objecttype in the output it is fine (which gives me a workaround). Or
if I use git cat-file --batch.

IIUC git only fetches the metadata that it needs for each object, and
that is determined from the format. For --batch I guess the type is
always requested, since it is needed to print the object contents. But
for --batch-command that doesn't seem to happen.

I'm not sure what the correct fix is - always request the type in
--batch-command, or perhaps only if a "contents" command is issued?


Please review the rest of the bug report below.
You can delete any lines you don't wish to share.


[System Info]
git version:
git version 2.54.0
cpu: x86_64
no commit associated with this build
sizeof-long: 8
sizeof-size_t: 8
shell-path: /bin/sh
rust: disabled
gettext: enabled
libcurl: 8.5.0
zlib: 1.3
SHA-1: SHA1_DC
SHA-256: SHA256_BLK
default-ref-format: files
default-hash: sha1
uname: Linux 7.0.0-28-generic #28~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC
Wed Jul  1 15:50:57 UTC 2 x86_64
compiler info: gnuc: 13.3
libc info: glibc: 2.39
$SHELL (typically, interactive shell): /bin/bash


[Enabled Hooks]

Best wishes,

Alan