gh pr merge --auto -d does not delete the branch after merge

[arcivanov]

Describe the bug

A successful gh pr merge --auto -d does not delete the branch after a successful merge. It's unclear whether it's GH CLI problem or GH API.

Steps to reproduce the behavior

The PR in question that didn't have a branch auto-deleted is here: karellen/karellen-llvm#40
The branch was marked for auto-merge and auto-delete here: https://github.com/karellen/karellen-llvm/actions/runs/9048046223/job/24860694266#step:4:62 (line 61)

If this is not something that can be fixed in GH CLI and GH API the documentation update is necessary to note that it's not an expected behavior.

Expected vs actual behavior

Expected: PR auto-merge will be followed by auto-delete if delete is requested.
Actual: The PR is automatically merged but the branch remains.

Logs

Above in the action items.

[williammartin]

Reading the code this is intentional behaviour when you provide --auto because as far as I know there is no way to tell the API to remember to delete the branch when the PR is automatically merged.

cli/pkg/cmd/pr/merge/merge.go

Lines 448 to 450 in af02889

	if !m.deleteBranch || m.crossRepoPR || m.autoMerge {
	return nil
	}

However, it's not clear to me why we allow both of these flags to be provided at the same time if this is the behaviour, instead of erroring and saying "you can't do that". This seems to have been the behaviour since the --auto flag was introduced. I agree with you that it is confusing.

[andyfeller]

Is the suggestion that we need to fail early if these confliction options are specified?

Reviewing the code, I see we have other places we're checking for mutually exclusive options:

cli/pkg/cmd/pr/merge/merge.go

Lines 129 to 136 in af02889

	if err := cmdutil.MutuallyExclusive(
	"specify only one of `--auto`, `--disable-auto`, or `--admin`",
	opts.AutoMergeEnable,
	opts.AutoMergeDisable,
	opts.UseAdmin,
	); err != nil {
	return err
	}

Reading through the rest of the code, m.deleteBranch is not derived directly from options:

cli/pkg/cmd/pr/merge/merge.go

Lines 583 to 601 in af02889

	func deleteBranchSurvey(opts *MergeOptions, crossRepoPR, localBranchExists bool) (bool, error) {
	if !opts.IsDeleteBranchIndicated {
	var message string
	if opts.CanDeleteLocalBranch && localBranchExists {
	if crossRepoPR {
	message = "Delete the branch locally?"
	} else {
	message = "Delete the branch locally and on GitHub?"
	}
	} else if !crossRepoPR {
	message = "Delete the branch on GitHub?"
	}
	return opts.Prompter.Confirm(message, false)
	}
	return opts.DeleteBranch, nil
	}

[williammartin]

Is the suggestion that we need to fail early if these confliction options are specified?

Yes, I can't see any reason that we would want to proceed in this case. I can't see any code path that would allow for the branch to be deleted if --auto is provided.