Support additional lint levels beyond warning and error

[euclio]

Some linters emit low-severity messages or additional information that is not considered a warning or an error. It would be useful to be able to represent these within ALE. For example, Neomake has 4 levels (error, warning, message, info).

[w0rp]

We'll have to look into this. I started initially only supporting the two flags that loclist supports, 'E' and 'W'`. We can add arbitrary keys into the loclist items, so maybe we could store more information on the objects for use in the statusline, etc.

[blueyed]

Does the loclist really support only "E" and "W"?

Related: neomake/neomake#584

[w0rp]

I just had a look at :help setqflist(), which is where :help setloclist() sends you. It says only this.

type    single-character error type, 'E', 'W', etc.

I guess by "etc." you can set other error types as long as you use a single character.

[blueyed]

Yep.

[euclio]

I'd like to try implementing this. Should I just add support for info and message levels?

[w0rp]

Yeah, go for it. Some work will need to be done for each linter, where the different error levels are available, and some work will be needed for signs, the statusline, etc.

[w0rp]

Type 'I' for "info", and style errors and warnings through sub_type 'style' are now supported for signs, but nothing else yet. Everything else still needs to be adjusted.

[w0rp]

I just pushed a commit so the status lines will continue to work if the other problem types are set. Now ale#statusline#Count() returns a Dictionary containing the keys total, error, warning, info, style_error, and style_warning, mapping to the counts for each. Two extra keys 0 and 1 are set so the Dictionary will continue to function with the airline extension here: https://github.com/vim-airline/vim-airline/blob/06351e86df61b79bd00971d6c2f33c286a048b22/autoload/airline/extensions/ale.vim#L11 The sum of error and style_error are set for 0, and the sum of warning, style_warning, and info are set for 1.

So the status functions should now tolerate the new problem types, and produce the current output.

[w0rp]

I pushed a commit for setting different syntax highlights for "info" items, style warnings, and style errors. Info and style warnings map to the highlights for warnings for now, and style errors map to the error highlights.

[w0rp]

Other types should be supported everywhere now. Individual linters will need to be updated to do something meaningful. Some better defaults can be set for highlights, etc., later. The new highlight groups have been documented.

I'll think about a new statusline format, which will also fix #323.