Show errors and warnings for the 'smlnj' linter

[cwfoo]

Fixes #3953

[cwfoo]

@hsanson @benknoble Please take a look.

[hsanson]

Looks good. Appreciated if @benknoble can test this before merging it.

[benknoble]

I will take a look tonight if I can

[benknoble]

Working on a single file looked fine. Working on a CM-based project worked fine, partly because ALE only uses one or the other (and prefers CM when it can).

Here is a failure I found:

• Put val b = 1 in b.sml, then open a new file (save or don't) and put use "b.sml"; val a: bool = b. SML reports issues, but I couldn't see them in ALE (they show up as errors for the file = stdIn: the SML repl doesn't handle some kinds of output too well, so there are occasional spurious - and = prefixes).

On a related note, if the error isn't in the file I'm currently looking at, :lopen shows it (or :copen, if you use quickfix). But ale#statusline#Count(bufnr('%')) doesn't report them. Perhaps that changed recently, but I thought it used to be a total count, not just the ones specific to that buffer.

[cwfoo]

I could change the regex from ^\(- = \)\?stdIn$ to stdIn$ and hope that no one ever uses filenames ending with "stdIn" for their SML source files (which should have a ".sml" extension anyway). What do you think?

[benknoble]

Saw the new commit: did you try it out on the case I mentioned? I haven't yet.

[benknoble]

If @cwfoo can confirm their latest commit fixes the case I mentioned, then I approve.

[cwfoo]

@benknoble With the latest commit (i.e. "Change smlnj stdIn regex"), ALE would show Error: pattern and expression in val dec don't agree [tycon mismatch] on the first line of a.sml in your a.sml/b.sml example.

(I tried to test this yesterday, but I was bitten by a CM file that I left in my home directory some time ago. ALE really prefers CM!).

[benknoble]

@benknoble With the latest commit (i.e. "Change smlnj stdIn regex"), ALE would show Error: pattern and expression in val dec don't agree [tycon mismatch] on the first line of a.sml in your a.sml/b.sml example.

Great, than I think is ready to merge @hsanson

(I tried to test this yesterday, but I was bitten by a CM file that I left in my home directory some time ago. ALE really prefers CM!).

Well, that's because CM should be preferred :) actually, it's because if there's a CM file, than there's likely no other way to correctly (try to) compile the file with SML/NJ—simply running it may not work if depends on modules declared in the CM file. OTOH, invoking it via CM is guaranteed to work. Granted, the CM file finder is a little… eager… in that it looks upwards and takes the first one it finds (even with multiple in the same directory). If there is a better way to handle this, suggestions are welcome.

[hsanson]

Thanks for the contribution.