Edge cases: No revdep, Pkg checked not installed, Pkg not on CRAN

[coatless]

Listing the edge cases in one issue as they have the same underlying error message and I'm trying to exceed 200 words 😎

Issues

1. Package lacks reverse dependencies. c.f. pkgKitten
2. Package not installed, could be from a typo et cetera. Would be nice if there was a warning...
3. Package not on CRAN

Error Diagnostics

All edge cases give warnings like:

inqueue <- enqueueJobs("pkgKitten", ".")
# Error: title is not a string (length 1 character)

outqueue <- dequeueJobs("pkgKitten", ".")
# NA_NA started at 2018-01-23 00:01:13 Warning in download.packages(tok[1], ".", quiet = TRUE) : 
# no package ‘NA’ at the repositories

Protection

Largely the case since:

Empty data.table (0 rows) of 2 cols: Package,Version

will be empty during:

prrd/R/enqueue.R

Lines 36 to 40 in e936686

	for (i in 1:n) {
	ttl <- paste0(work[i,Package])
	msg <- paste(work[i,Package], work[i, Version], sep="_")
	publish(q, title = ttl, message = msg)
	}

I think one bit we discussed was adding with = FALSE (data.table's drop = FALSE) inside the work subset

[eddelbuettel]

Part is fixiing 1:n for the loop to seq_len(nrow(work)) but that still needs special for empty, and single row.

[eddelbuettel]

"Package not on CRAN" is not valid; you may have different options(repos) -- we have a local-to-work drat repo at work. "Somewhere in available.packages() output" is a better test.

[eddelbuettel]

"Not installed" is not valid I think.

[eddelbuettel]

This really reduced down to one additional check, and that I made. The n=1 case is taken care of by data.table.

[coatless]

Great! I'll give it a whirl and see if I can break it more 😃