Slurm resource named clusters in docs, and cluster in getClusters

[jemus42]

I can't quite decide which way it is.

In clusterFunctionsSlurm.R, the getClusters function is defined which looks for a resource named cluster (singular).

batchtools/R/clusterFunctionsSlurm.R

Lines 38 to 42 in 1196047

	getClusters = function(reg) {
	clusters = filterNull(lapply(reg$resources$resources, "[[", "cluster"))
	if (length(clusters))
	return(stri_flatten(unique(as.character(clusters)), ","))
	return(character(0L))

The documentation of submitJobs refers to clusters (plural):

batchtools/R/submitJobs.R

Line 25 in 1196047

#' \item{clusters:}{Resource used for Slurm to select the set of clusters to run \code{sbatch}/\code{squeue}/\code{scancel} on.}

The problem:

if this resource / getClusters is NULL, there's no cluster specified and functions like findRunning() etc. will return an empty table despite jobs are running.
For months I was wondering why my queued Slurm jobs where listed as expired and I assumed I was doing something wrong or my template was outdated.
Took me a moment to figure out that I was accidentally correctly misspecifying clusters in my resources = list(...) call 🥴

EDIT: Oh, and the template I'm using relies on resources$clusters.

Suggested fix

I'm not sure. I was about to prepare a PR when I realized that I don't want to

• change the internal getClusters function to look for clusters instead of cluster because that will silently break peoples existing batchtools configs and they might not notice.
• change the docs for submitJobs to (wrongly?) suggest that the resource should be named cluster, implying that multiple clusters can not be specified (which I never tried)

At the very least I thought about introducing an assertion on provided resources to shield against this sort of thing, but I'm not sure how to go about that yet.