#1889 Add support for automatically previewing messages based on the cursor position

autoload/ale/cursor.vim

@@ -1,4 +1,6 @@
+scriptencoding utf-8
 " Author: w0rp <devw0rp@gmail.com>
+" Author: João Paulo S. de Souza <joao.paulo.silvasouza@hotmail.com>
 " Description: Echoes lint message for the current line, if any
 
 " Controls the milliseconds delay before echoing a message.
@@ -37,12 +39,11 @@ function! ale#cursor#TruncatedEcho(original_message) abort
     endtry
 endfunction
 
-function! s:FindItemAtCursor() abort
-    let l:buf = bufnr('')
-    let l:info = get(g:ale_buffer_info, l:buf, {})
+function! s:FindItemAtCursor(buffer) abort
+    let l:info = get(g:ale_buffer_info, a:buffer, {})
     let l:loclist = get(l:info, 'loclist', [])
     let l:pos = getcurpos()
-    let l:index = ale#util#BinarySearch(l:loclist, l:buf, l:pos[1], l:pos[2])
+    let l:index = ale#util#BinarySearch(l:loclist, a:buffer, l:pos[1], l:pos[2])
     let l:loc = l:index >= 0 ? l:loclist[l:index] : {}
 
     return [l:info, l:loc]
@@ -56,7 +57,9 @@ function! s:StopCursorTimer() abort
 endfunction
 
 function! ale#cursor#EchoCursorWarning(...) abort
-    if !g:ale_echo_cursor
+    let l:buffer = bufnr('')
+
+    if !g:ale_echo_cursor && !g:ale_cursor_detail
         return
     endif
 
@@ -65,28 +68,39 @@ function! ale#cursor#EchoCursorWarning(...) abort
         return
     endif
 
-    if ale#ShouldDoNothing(bufnr(''))
+    if ale#ShouldDoNothing(l:buffer)
         return
     endif
 
-    let l:buffer = bufnr('')
-    let [l:info, l:loc] = s:FindItemAtCursor()
+    let [l:info, l:loc] = s:FindItemAtCursor(l:buffer)
 
-    if !empty(l:loc)
-        let l:format = ale#Var(l:buffer, 'echo_msg_format')
-        let l:msg = ale#GetLocItemMessage(l:loc, l:format)
-        call ale#cursor#TruncatedEcho(l:msg)
-        let l:info.echoed = 1
-    elseif get(l:info, 'echoed')
-        " We'll only clear the echoed message when moving off errors once,
-        " so we don't continually clear the echo line.
-        execute 'echo'
-        let l:info.echoed = 0
+    if g:ale_echo_cursor
+        if !empty(l:loc)
+            let l:format = ale#Var(l:buffer, 'echo_msg_format')
+            let l:msg = ale#GetLocItemMessage(l:loc, l:format)
+            call ale#cursor#TruncatedEcho(l:msg)
+            let l:info.echoed = 1
+        elseif get(l:info, 'echoed')
+            " We'll only clear the echoed message when moving off errors once,
+            " so we don't continually clear the echo line.
+            execute 'echo'
+            let l:info.echoed = 0
+        endif
+    endif
+
+    if g:ale_cursor_detail
+        if !empty(l:loc)
+            call s:ShowCursorDetailForItem(l:loc, {'stay_here': 1})
+        else
+            call ale#preview#CloseIfTypeMatches('ale-preview')
+        endif
     endif
 endfunction
 
 function! ale#cursor#EchoCursorWarningWithDelay() abort
-    if !g:ale_echo_cursor
+    let l:buffer = bufnr('')
+
+    if !g:ale_echo_cursor && !g:ale_cursor_detail
         return
     endif
 
@@ -104,7 +118,7 @@ function! ale#cursor#EchoCursorWarningWithDelay() abort
     " we should echo something. Otherwise we can end up doing processing
     " the echo message far too frequently.
     if l:pos != s:last_pos
-        let l:delay = ale#Var(bufnr(''), 'echo_delay')
+        let l:delay = ale#Var(l:buffer, 'echo_delay')
 
         let s:last_pos = l:pos
         let s:cursor_timer = timer_start(
@@ -114,24 +128,37 @@ function! ale#cursor#EchoCursorWarningWithDelay() abort
     endif
 endfunction
 
+function! s:ShowCursorDetailForItem(loc, options) abort
+    let l:stay_here = get(a:options, 'stay_here', 0)
+
+    let s:last_detailed_line = line('.')
+    let l:message = get(a:loc, 'detail', a:loc.text)
+    let l:lines = split(l:message, "\n")
+    call ale#preview#Show(l:lines, {'stay_here': l:stay_here})
+
+    " Clear the echo message if we manually displayed details.
+    if !l:stay_here
+        execute 'echo'
+    endif
+endfunction
+
 function! ale#cursor#ShowCursorDetail() abort
+    let l:buffer = bufnr('')
+
     " Only echo the warnings in normal mode, otherwise we will get problems.
     if mode() isnot# 'n'
         return
     endif
 
-    if ale#ShouldDoNothing(bufnr(''))
+    if ale#ShouldDoNothing(l:buffer)
         return
     endif
 
     call s:StopCursorTimer()
 
-    let [l:info, l:loc] = s:FindItemAtCursor()
+    let [l:info, l:loc] = s:FindItemAtCursor(l:buffer)
 
     if !empty(l:loc)
-        let l:message = get(l:loc, 'detail', l:loc.text)
-
-        call ale#preview#Show(split(l:message, "\n"))
-        execute 'echo'
+        call s:ShowCursorDetailForItem(l:loc, {'stay_here': 0})
     endif
 endfunction

autoload/ale/events.vim

@@ -131,13 +131,17 @@ function! ale#events#Init() abort
                 autocmd InsertLeave * call ale#Queue(0)
             endif
 
-            if g:ale_echo_cursor
+            if g:ale_echo_cursor || g:ale_cursor_detail
                 autocmd CursorMoved,CursorHold * if exists('*ale#engine#Cleanup') | call ale#cursor#EchoCursorWarningWithDelay() | endif
                 " Look for a warning to echo as soon as we leave Insert mode.
                 " The script's position variable used when moving the cursor will
                 " not be changed here.
                 autocmd InsertLeave * if exists('*ale#engine#Cleanup') | call ale#cursor#EchoCursorWarning() | endif
             endif
+
+            if g:ale_close_preview_on_insert
+                autocmd InsertEnter * if exists('*ale#preview#CloseIfTypeMatches') | call ale#preview#CloseIfTypeMatches('ale-preview') | endif
+            endif
         endif
     augroup END
 endfunction

autoload/ale/preview.vim

@@ -15,13 +15,13 @@ function! ale#preview#Show(lines, ...) abort
     setlocal modifiable
     setlocal noreadonly
     setlocal nobuflisted
-    let &l:filetype = get(l:options, 'filetype', 'ale-preview')
     setlocal buftype=nofile
     setlocal bufhidden=wipe
     :%d
     call setline(1, a:lines)
     setlocal nomodifiable
     setlocal readonly
+    let &l:filetype = get(l:options, 'filetype', 'ale-preview')
 
     if get(l:options, 'stay_here')
         wincmd p