edge cases in broken templates give odd errors

[kadoban]

These are rather dumb, but I could still see them coming up in practice and it might not be the worst idea to handle them:

Blank Template

Steps to Reproduce

~$ touch blah.hsfiles
~$ stack new blah blah
Downloading template "blah" to create project "blah" in blah/ ...
/home/mud/blah/: getDirectoryContents: does not exist (No such file or directory)

Expected

An error message about the template being empty.

Template without .cabal

Steps to Reproduce

~$ printf "{-# START_FILE BOGUS #-}\n" > blah.hsfiles
~$ stack new blah blah
Downloading template "blah" to create project "blah" in blah/ ...
Writing default config file to: /home/mud/blah/stack.yaml
Basing on cabal files:

In order to init, you should have an existing .cabal file. Please try "stack new" instead

Expected

Either an inited package or (since that's probably not really sane without a .cabal file) a better error message about the template being broken. Edit: I just noticed that it works file with an empty .cabal file, so maybe it would make sense for stack.yaml to do the same thing when .cabal doesn't exist?

In particular it's kind of amusing, but not really helpful, that it tells you to run "stack new" when that's what you just tried.

If there's a real use for a template that doesn't include a .cabal file (I can't think of one, but maybe someone else can), it might be acceptable to just have a big warning about why init didn't do anything, and ideally remove the suggestion about "stack new".

Version

Version 0.1.10.1, Git revision 83ec40fc5fd6d300c73d23deb1f41d30168fc236 (2783 commits) x86_64

[mgsloan]

Makes sense to me, seems like a good thing to fix.

[kadoban]

I've got a fix for the first part (give a better error in case of a blank template) in 019dd75, I'm not entirely sure what to do about a missing .cabal file though. Options I can think of:

1. Give an error always if there is no .cabal file.
2. Make a --no-init option to stack new which will have it skip the init step. If initing is to be done, give an error if there is no .cabal file, otherwise maybe give a warning.
3. Just skip the init step automatically if there is no .cabal file.
4. "Fix" init so that it handles the case where there's no .cabal file similarly to how it handles the case where you have an empty .cabal file (it creates a stack.yaml, apparently just specifying the latest lts resolver, fine and doesn't really care that .cabal is empty).

I am not really sure what the desired outcome should be here, anyone have any thoughts? I originally thought it should just be an error, but I'm starting to wonder what it would actually hurt allowing that.

[mgsloan]

I'm in favor of option (1). My reasoning for each option:

(1) Seems fine, since it's unlikely that templates will intentionally lack a cabal file
(2) Let's wait until someone needs this, I don't think anyone will
(3) See reasoning for (1)
(4) "init" is useful for its handling of cabal files. People might initially misunderstand its usage if it succeeds in the absence of cabal files.

[kadoban]

Sounds like good reasoning to me, thanks.