Add 'intero' filetype, use for syntax highlighting

[jez]

Following up from #64, I've pulled a few changes together into an MVP of syntax highlighting an intero terminal buffer:

• Haskell code is highlighted
• GHCi :foo commands are highlighted

It doesn't do much context-aware highlighting for individual commands yet, because I didn't know which ones were worth supporting. I mostly just use :t, :i, :type-at, and :l, which are all pretty well supported without much effort.

[jez]

Updated: screenshot in description.

[rdnetto]

Awesome! :)

One nit: it only highlights the > in the prompt instead of everything before it, and then only if you have typed something on the same line.

This doesn't really matter though, as if it contains escape codes they get passed through anyway, and I suspect most users will do this anyway to get a coloured prompt when using stack ghci. So if you're not fussed about that, I'm happy to merge it.

[jez]

Oh that’s a good catch! I’ll poke around at that before we merge. On Sat, Jan 27, 2018 at 8:00 PM rdnetto notifications@github.com wrote:

Awesome! :)

One nit: it only highlights the > in the prompt instead of everything before it, and then only if you have typed something on the same line.

This doesn't really matter though, as if it contains escape codes they get passed through anyway, and I suspect most users will do this anyway to get a coloured prompt when using stack ghci. So if you're not fussed about that, I'm happy to merge it.

[image: intero_syntax] https://user-images.githubusercontent.com/1973389/35478809-4b223b38-043b-11e8-9f6f-964ce8c48ad6.png

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[parsonsmatt]

@jez Any progress on that point?

[jez]

Ah, sorry for the radio silence on this! I haven't had much time lately, but today I do! I'll take another look at this and hopefully we can merge today or tomorrow.

[parsonsmatt]

No worries, I haven't been able to put much energy into this either :) Thanks!

[jez]

Solarized Light	Solarized Dark

Actual colors will differ based on your installed colorscheme.

It's possible to override the default colors here by setting values for the color groups in your vimrc (i.e., we only provide default mappings if none are specified earlier—see comment about this in the code).

Features exemplified in the screenshots:

• various GHCi commands (:kind, :type-at, :load)
• some GHC output (loading modules, expected/actual errors, probable cause errors)
• Haskell syntax on a GHCi prompt line
  • This is very rudimentary right now. Anything contained within brackets is not highlighted. I have some idea about the cause, but I see no obvious solution.

This is just a start! Future work:

• [ ] Only highlight recognized GHCi commands (right now, we highlight anything after a :, even if the command is invalid).
• [ ] More highlighting for GHC output to make it easier to parse error messages.
• [ ] Fix the "no highlighting within brackets" bug.

Also: @rdnetto I think that I fixed the issue you were seeing where part of your prompt was getting highlighted as if it were Haskell syntax. I'd love it if you could confirm this!

[jez]

Just added one more potential thing to highlight on GHCi output.

@parsonsmatt @rdnetto bump on this?

[parsonsmatt]

Screenshots?

EDIT: Ah, you already posted some! If you're happy with this, then I am good to merge.