Don't call error when no tutorials are found

[byorgey]

If no tutorials are found, we currently simply crash with a call to error. I don't know how to reproduce, but one of my students somehow got Swarm installed and running but in such a way that it apparently could not find the data files, so it crashed with a message saying "No first tutorial found!".

We should instead somehow generate a nice error message explaining the problem.

See also #1494 .

[xsebek]

I don't know how to reproduce

Maybe they copied the data files but not the inner folders? 🤔 Something like:

mkdir -p ~/.local/share/swarm/data/scenarios; cp data/scenarios/* ~/.local/share/swarm/data/scenarios/
# cp: data/scenarios/Tutorials is a directory (not copied).

We should instead somehow generate a nice error message explaining the problem.

What if, in addition to adding the warning message to Messages, we made the Tutorials menu red and, when selected, opened a dialog popup explaining that the data files are missing?

It would be extra work, but we could reuse that for New Game when all data files are missing.

[byorgey]

Maybe they copied the data files but not the inner folders?

The student in question was definitely not that sophisticated in their use of the command line. They just cloned the repo and ran cabal run -O0 swarm:exe:swarm. This failed at first, e.g. because we had to install a few missing distro packages, but eventually it succeeded... but with no data files. We did various combinations of cabal clean, cabal build, cabal install but none of them fixed the issue. Eventually we just abandoned the repo and did cabal install swarm to download and build it from Hackage, which succeeded. Seems like ultimately some sort of bug in cabal but I wouldn't have the faintest idea how to go about reproducing, much less diagnosing, it.

Anyway, the ultimate point is that this can happen, so we should handle it gracefully.

What if, in addition to adding the warning message to Messages, we made the Tutorials menu red and, when selected, opened a dialog popup explaining that the data files are missing?

It would be extra work, but we could reuse that for New Game when all data files are missing.

That sounds like a nice idea!