Use haskell-check-command for flymake-init

[andrewsw]

Instead of the default nil of haskell-saved-check-command, uses
haskell-check-command to ensure we have something reasonable to run.

Fixes #384

[purcell]

Great, but this isn't just the default: I think we'd want something like (or haskell-saved-check-command haskell-check-command) so that the user's command takes precedence once set. Could you amend this PR accordingly?

P.S. Also look into Flycheck if you haven't already. It renders flymake obsolete. :-)

[andrewsw]

I experimented with your proposed change and it doesn't necessarily work the way one would expect.

haskell-saved-check-command will be set by use of haskell-check, which is great, but haskell-check doesn't infer the file name. So to use haskell-check, you have to provide not only the command to run, but also it's arguments and the target file name which is all stored in haskell-saved-check-command. This is great for obvious reasons, when using haskell-check, but not so good for flymake because flymake assumes it only has the checking command and not the target -- constructing the target temporary file and appending it's name to the end of the command.

In the end, either there has to be a lot more machinery in place to make fuzzy attempts at removing the target filename from haskell-saved-check-command when using it in flymake, or do something completely different. How about I make another variable... haskell-flymake-check-command to disambiguate the uses?

And yes, I'll investigate flycheck at some point. If flymake is obsolete, maybe it should be removed from haskell-mode?

[andrewsw]

updated with my suggestion.

[purcell]

If flymake is obsolete, maybe it should be removed from haskell-mode?

Yes, possibly, though flycheck doesn't work with Emacs 23, which haskell-mode still nominally supports.

[chrisdone]

If it's of interest I'm going to add flycheck support to haskell-interactive-mode this weekend, after merging in #381.

[purcell]

I'm going to add flycheck support to haskell-interactive-mode this weekend

How will that work? You mean the interactive expressions will get flychecked as they are typed?

[chrisdone]

I mean checking files using the haskell-process module.

[purcell]

Aha, so that will be a custom flycheck checker which hooks into the haskell-process machinery? Sounds like it could be a nice alternative to the flycheck-haskell code.

Presumably this would then live in a separate repo and be a package which would depend on both haskell-mode and flycheck?

[chrisdone]

Yeah, probably.

[gracjan]

@chrisdone ? @purcell ? Can/should this pull by @andrewsw be merged?

[purcell]

Not in its current form, I'd say. This change removes haskell-saved-check-command from the picture, but that var is still set from elsewhere, and some people will likely be accustomed to running the checker explicitly first in order to set it.

I'd suggest that when running the check manually, the default command should be taken from this new haskell-flymake-check-command variable, and that haskell-saved-check-command should still be used (if set) as the flymake command.

[gracjan]

@andrewsw: Are you able to change your commit so that it conforms to what @purcell says?

[andrewsw-janrain]

@gracjan , yes probably. Sorry, I've been heavily distracted at work and hadn't gotten back to it. I'll try this weekend, but won't object if someone beats me to it.

[gracjan]

It seems that this one is stalled. If anybody finds time to push this forward do no hesitate to reopen or create a new pull request.