Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

Git submodule fials if branch not present

Open
#1,361 0 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
58/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Stale
Tech stack
git, python
Domain
devtools

Research direction

Start in pygit2/submodules.py at the Submodule.branch property and inspect how C.git_submodule_branch returns an unset branch. Verify the behavior for a submodule without a configured branch and confirm that accessing the property no longer raises the reported NULL cdata RuntimeError.

Written by the indexing model from the issue text.

Description

In case if I want to check if branch was provided to submodule and it is not provided I got error

  if sm.branch:
      name = f"{sm.branch}/{sm.name}"
  else:
      name = f"{sm.name}"

File "/app/venv/lib/python3.11/site-packages/pygit2/submodules.py", line 148, in branch return ffi.string(branch).decode('utf-8') ^^^^^^^^^^^^^^^^^^ RuntimeError: cannot use string() on <cdata 'char *' NULL>

It looks like there is missing check if branch is actually set

class Submodule:
...

@property
def branch(self):
    """Branch that is to be tracked by the submodule."""
    branch = C.git_submodule_branch(self._subm)
    return ffi.string(branch).decode('utf-8')

I think it should be like this

@property
def branch(self):
    """Branch that is to be tracked by the submodule."""
    branch = C.git_submodule_branch(self._subm)
    if branch:
        return ffi.string(branch).decode('utf-8')
Dominant language
Python
Stars
1.7k
Forks
408
Avg merge
2d 57m
Merged PRs (30d)
7

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from libgit2/pygit2

All issues in libgit2/pygit2

Similar issues

More Python issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.