Add support for error details

Some review needed.

ale_linters/elm/make.vim

@@ -25,6 +25,7 @@ function! ale_linters#elm#make#Handle(buffer, lines) abort
                     \    'col': l:error.region.start.column,
                     \    'type': (l:error.type ==? 'error') ? 'E' : 'W',
                     \    'text': l:error.overview,
+                    \    'detail': l:error.overview . "\n\n" . l:error.details
                     \})
                 endif
             endfor

autoload/ale/cursor.vim

@@ -93,3 +93,28 @@ function! ale#cursor#EchoCursorWarningWithDelay() abort
         let s:cursor_timer = timer_start(10, function('ale#cursor#EchoCursorWarning'))
     endif
 endfunction
+
+
+function! ale#cursor#ShowCursorDetail(...) abort
+    " Only show the details in normal mode, otherwise we will get problems.
+    if mode() !=# 'n'
+        return
+    endif
+
+    let l:buffer = bufnr('%')
+
+    if !has_key(g:ale_buffer_info, l:buffer)
+        return
+    endif
+
+    let l:pos = getcurpos()
+    let l:loclist = g:ale_buffer_info[l:buffer].loclist
+    let l:index = ale#util#BinarySearch(l:loclist, l:pos[1], l:pos[2])
+
+    if l:index >= 0
+        let l:loc = l:loclist[l:index]
+        if has_key(l:loc, 'detail')
+            echo l:loc.detail
+        endif
+    endif
+endfunction

autoload/ale/engine.vim

@@ -332,6 +332,10 @@ function! ale#engine#FixLocList(buffer, linter, loclist) abort
         \   'linter_name': a:linter.name,
         \}
 
+        if has_key(l:old_item, 'detail')
+            let l:item.detail = l:old_item.detail
+        endif
+
         if l:item.lnum == 0
             " When errors appear at line 0, put them at line 1 instead.
             let l:item.lnum = 1

plugin/ale.vim

@@ -208,6 +208,9 @@ command! ALEPreviousWrap :call ale#loclist_jumping#Jump('before', 1)
 command! ALENext :call ale#loclist_jumping#Jump('after', 0)
 command! ALENextWrap :call ale#loclist_jumping#Jump('after', 1)
 
+" A command for showing error details.
+command! ALEDetail :call ale#cursor#ShowCursorDetail()
+
 " A command for turning ALE on or off.
 command! ALEToggle :call s:ALEToggle()
 " A command for linting manually.
@@ -225,6 +228,7 @@ nnoremap <silent> <Plug>(ale_next) :ALENext<Return>
 nnoremap <silent> <Plug>(ale_next_wrap) :ALENextWrap<Return>
 nnoremap <silent> <Plug>(ale_toggle) :ALEToggle<Return>
 nnoremap <silent> <Plug>(ale_lint) :ALELint<Return>
+nnoremap <silent> <Plug>(ale_detail) :ALEDetail<Return>
 
 " Housekeeping
 

test/test_cursor_warnings.vader

@@ -10,7 +10,8 @@ Before:
   \       'nr': -1,
   \       'type': 'E',
   \       'col': 10,
-  \       'text': 'Missing semicolon. (semi)'
+  \       'text': 'Missing semicolon. (semi)',
+  \       'detail': 'Every statement should end with a semicolon'
   \     },
   \     {
   \       'lnum': 2,
@@ -84,3 +85,14 @@ Then(Check the cursor output):
   let g:lines = split(g:output, "\n")
 
   AssertEqual 'Missing radix parameter (radix)', g:lines[-1]
+
+Execute(Evaluate the cursor detail function at line 1):
+  :1
+  call ale#cursor#ShowCursorDetail()
+
+Then(Check the cursor output):
+  redir => g:output
+    :mess
+  redir END
+
+  AssertEqual "Every statement should end with a semicolon", g:output[-1]