With update_existing=false, evergreen ignores existing config file if the extension doesn't match the first one defined in filename_list

[detiber]

Describe the bug

It looks like a bug was introduced post 1.10.8 with the introduction of support for updating existing configs, when update_existing is false and the existing configuration file extension does not match the first one defined in filename_list:

evergreen/evergreen.py

Lines 82 to 89 in ff2f3ff

	existing_config = None
	filename_list = [".github/dependabot.yaml", ".github/dependabot.yml"]
	dependabot_filename_to_use = filename_list[0] # Default to the first filename
	for filename in filename_list:
	existing_config = check_existing_config(repo, filename, update_existing)
	if existing_config:
	dependabot_filename_to_use = filename
	break

evergreen/evergreen.py

Lines 210 to 234 in ff2f3ff

	def check_existing_config(repo, filename, update_existing):
	"""
	Check if the dependabot file already exists in the
	repository and return the existing config if it does
	Args:
	repo (github3.repos.repo.Repository): The repository to check
	filename (str): The dependabot configuration filename to check
	update_existing (bool): Whether to update existing dependabot configuration files
	Returns:
	github3.repos.contents.Contents | None: The existing config if it exists, otherwise None
	"""
	existing_config = None
	try:
	existing_config = repo.file_contents(filename)
	if existing_config.size > 0:
	if not update_existing:
	print(
	"Skipping " + repo.full_name + " (dependabot file already exists)"
	)
	return None
	except github3.exceptions.NotFoundError:
	pass
	return existing_config

Because check_existing_config eats the exception and returns None when the file doesn't exist and also returns None when the file exists AND update_existing=false, dependabot_filename_to_use is always filename_list[0], so if there is a pre-existing file with the name filename_list[1], then a PR will be created despite a dependabot config already being present.

This also results in the confusing job output:

Skipping org/repo (dependabot file already exists)
Checking org/repo for compatible package managers
	Created pull request https://github.com/org/repo/pull/41

To Reproduce

See above

Expected behavior

Dependabot not to create a PR when update_existing=false, a dependabot config already exists, and the existing file has any supported file extension, not just the default one.

Screenshots

No response

Additional context

I'd suggest that either:

• check_existing_config provide the caller a way to differentiate between the file not existing and it existing, but should not be updated
• refactor the calling code to handle testing for existing config vs whether to update the existing config, similar to below:

        for filename in filename_list:
            existing_config = check_existing_config(repo, filename)
            if existing_config:
                dependabot_filename_to_use = filename

        if existing_config and not update_existing:
            print(
                "Skipping " + repo.full_name + " (dependabot file already exists)"
            )
            continue

def check_existing_config(repo, filename, update_existing):
    """
    Check if the dependabot file already exists in the
    repository and return the existing config if it does

    Args:
        repo (github3.repos.repo.Repository): The repository to check
        filename (str): The dependabot configuration filename to check

    Returns:
        github3.repos.contents.Contents | None: The existing config if it exists, otherwise None
    """
    existing_config = None
    try:
        existing_config = repo.file_contents(filename)
        if existing_config.size > 0:
            return existing_config
        else:
            return None
    except github3.exceptions.NotFoundError:
        pass
    return existing_config

Do note, that I have not even verified the above code will parse, let alone function correctly.

[zkoppert]

@detiber Thanks for opening this bug report! I'm taking a look into this today.

[zkoppert]

Pull request open for review! Thanks again @detiber !

[detiber]

Thanks for the quick fix :)