TUI / GUI tooltip with content from ALEHover (#1556)

* Guard the ballooneval settings

* Mark main objectives to do to get nice Hover

* Make tweaks to make the tooltip work - See " XXX: comments

* Guard balloon_show call

* Use return instead of finish for functions

* ale#hover#show : Add optional arguments to specify arbtirary position

This change is requested to be able to call the function with mouse
position to enable hover information in vim's balloon

* ale#ballon#Disable : Remove feature guards

* ale#balloon : Show 'ALEHover' output on balloon if no diagnostic found

* ale#hover#HandleLSPResponse : remove the check for cursor position

This check prevented the 'ALEHover in balloon' feature, since mouse
position is almost never cursor position.

* ale#balloon#MessageForPos : Change the return of balloonexpr

balloonexpr evaluation now works even without balloon_show for basic
diagnostics, leaving the balloon_show call to ale#hover#Show, which can
then feature guard the call to avoid errors

* ale#hover#Response : Feature guard balloon_show calls

* ale#hover : always display 'Hover' information in messages

Also add a small comment to warn readers the different outputs the
ale#hover#Show will write to

* {LSP,TS}Response : use only variables from the Response

It is clearer that we only rely on l:options to get the relevant data to
build the LSP Response string

* hover#ShowDetails : fix an issue where not having focus broke balloons

The issue was caused by not using a buffer-specific version of getline()
to cap the value of the column sent in the message to LSP. Therefore a
cursor on column 10 in an inactive window could send a message with
column=0, if the active window had a buffer with too few lines

* {LSP,TS}Response : Remove redundant checks for balloon_show call

With the upcoming change in ale_set_balloons default value (see Pull
Request w0rp/ale#1565), this check will be useless

* balloonexpr? : Add a flag to separate hover#Show() calls

The goal of this flag is to make `:ALEHover` calls not pop a balloon
under the cursor, since the user has probably no interest in their
cursor while typing the command

The flag is a default argument which is overridden only in ballonexpr
call of ale#hover#Show, and stays set in the hover_map until the
callback for the LSP handles it.

There are no automated tests for this feature right now, and the nature
of the addition (one optional argument in the API) should make it
transparent to existing tests.

Since the differentiation is now possible, the check for moved cursor
has been put back in ale#hover#HandleLSPResponse

* ale#hover#hover_map : Protect accesses to hover_map

Using get() is safer than trying to access directly with ., as the tests
show.

* Raise timeout to try to get Appveyor happy

* Review : Fix comments

* Review : pass the optional argument 'called_from_balloonexpr' in a Dict

This optional dictionary has documentation just before the function
using it, ale#hover#Show, and allows easier extension in the future.

2 files changed, 72 insertions, 29 deletions

diff --git a/autoload/ale/balloon.vim b/autoload/ale/balloon.vim
index 552ced82..d36dd4f5 100644
--- a/autoload/ale/balloon.vim
+++ b/autoload/ale/balloon.vim
@@ -12,7 +12,13 @@ function! ale#balloon#MessageForPos(bufnr, lnum, col) abort
     let l:loclist = get(g:ale_buffer_info, a:bufnr, {'loclist': []}).loclist
     let l:index = ale#util#BinarySearch(l:loclist, a:bufnr, a:lnum, a:col)
 
-    return l:index >= 0 ? l:loclist[l:index].text : ''
+    " Show the diagnostics message if found, 'Hover' output otherwise
+    if l:index >= 0
+        return l:loclist[l:index].text
+    else
+        call ale#hover#Show(a:bufnr, a:lnum, a:col, {'called_from_balloonexpr': 1})
+        return ''
+    endif
 endfunction
 
 function! ale#balloon#Expr() abort
@@ -20,9 +26,22 @@ function! ale#balloon#Expr() abort
 endfunction
 
 function! ale#balloon#Disable() abort
-    set noballooneval balloonexpr=
+    set noballooneval noballoonevalterm
+    set balloonexpr=
 endfunction
 
 function! ale#balloon#Enable() abort
-    set ballooneval balloonexpr=ale#balloon#Expr()
+    if !has('balloon_eval') && !has('balloon_eval_term')
+        return
+    endif
+
+    if has('balloon_eval')
+        set ballooneval
+    endif
+
+    if has('balloon_eval_term')
+        set balloonevalterm
+    endif
+
+    set balloonexpr=ale#balloon#Expr()
 endfunction
diff --git a/autoload/ale/hover.vim b/autoload/ale/hover.vim
index 12af877d..3bf92488 100644
--- a/autoload/ale/hover.vim
+++ b/autoload/ale/hover.vim
@@ -24,7 +24,13 @@ function! ale#hover#HandleTSServerResponse(conn_id, response) abort
 
         if get(a:response, 'success', v:false) is v:true
         \&& get(a:response, 'body', v:null) isnot v:null
-            call ale#util#ShowMessage(a:response.body.displayString)
+            if get(l:options, 'hover_from_balloonexpr', 0)
+            \&& exists('*balloon_show')
+            \&& ale#Var(l:options.buffer, 'set_balloons')
+                call balloon_show(a:response.body.displayString)
+            else
+                call ale#util#ShowMessage(a:response.body.displayString)
+            endif
         endif
     endif
 endfunction
@@ -34,15 +40,18 @@ function! ale#hover#HandleLSPResponse(conn_id, response) abort
     \&& has_key(s:hover_map, a:response.id)
         let l:options = remove(s:hover_map, a:response.id)
 
-        let l:buffer = bufnr('')
-        let [l:line, l:column] = getcurpos()[1:2]
-        let l:end = len(getline(l:line))
-
-        if l:buffer isnot l:options.buffer
-        \|| l:line isnot l:options.line
-        \|| min([l:column, l:end]) isnot min([l:options.column, l:end])
-            " Cancel display the message if the cursor has moved.
-            return
+        " If the call did __not__ come from balloonexpr...
+        if !get(l:options, 'hover_from_balloonexpr', 0)
+            let l:buffer = bufnr('')
+            let [l:line, l:column] = getcurpos()[1:2]
+            let l:end = len(getline(l:line))
+
+            if l:buffer isnot l:options.buffer
+            \|| l:line isnot l:options.line
+            \|| min([l:column, l:end]) isnot min([l:options.column, l:end])
+                " ... Cancel display the message if the cursor has moved.
+                return
+            endif
         endif
 
         " The result can be a Dictionary item, a List of the same, or null.
@@ -71,21 +80,24 @@ function! ale#hover#HandleLSPResponse(conn_id, response) abort
             let l:str = substitute(l:str, '^\s*\(.\{-}\)\s*$', '\1', '')
 
             if !empty(l:str)
-                call ale#util#ShowMessage(l:str)
+                if get(l:options, 'hover_from_balloonexpr', 0)
+                \&& exists('*balloon_show')
+                \&& ale#Var(l:options.buffer, 'set_balloons')
+                    call balloon_show(l:str)
+                else
+                    call ale#util#ShowMessage(l:str)
+                endif
             endif
         endif
     endif
 endfunction
 
-function! s:ShowDetails(linter) abort
-    let l:buffer = bufnr('')
-    let [l:line, l:column] = getcurpos()[1:2]
-
+function! s:ShowDetails(linter, buffer, line, column, opt) abort
     let l:Callback = a:linter.lsp is# 'tsserver'
     \   ? function('ale#hover#HandleTSServerResponse')
     \   : function('ale#hover#HandleLSPResponse')
 
-    let l:lsp_details = ale#linter#StartLSP(l:buffer, a:linter, l:Callback)
+    let l:lsp_details = ale#linter#StartLSP(a:buffer, a:linter, l:Callback)
 
     if empty(l:lsp_details)
         return 0
@@ -95,34 +107,46 @@ function! s:ShowDetails(linter) abort
     let l:root = l:lsp_details.project_root
 
     if a:linter.lsp is# 'tsserver'
+        let l:column = a:column
+
         let l:message = ale#lsp#tsserver_message#Quickinfo(
-        \   l:buffer,
-        \   l:line,
+        \   a:buffer,
+        \   a:line,
         \   l:column
         \)
     else
         " Send a message saying the buffer has changed first, or the
         " hover position probably won't make sense.
-        call ale#lsp#Send(l:id, ale#lsp#message#DidChange(l:buffer), l:root)
+        call ale#lsp#Send(l:id, ale#lsp#message#DidChange(a:buffer), l:root)
 
-        let l:column = min([l:column, len(getline(l:line))])
+        let l:column = min([a:column, len(getbufline(a:buffer, a:line)[0])])
 
-        let l:message = ale#lsp#message#Hover(l:buffer, l:line, l:column)
+        let l:message = ale#lsp#message#Hover(a:buffer, a:line, l:column)
     endif
 
     let l:request_id = ale#lsp#Send(l:id, l:message, l:root)
 
     let s:hover_map[l:request_id] = {
-    \   'buffer': l:buffer,
-    \   'line': l:line,
+    \   'buffer': a:buffer,
+    \   'line': a:line,
     \   'column': l:column,
+    \   'hover_from_balloonexpr': get(a:opt, 'called_from_balloonexpr', 0),
     \}
 endfunction
 
-function! ale#hover#Show() abort
-    for l:linter in ale#linter#Get(&filetype)
+" Obtain Hover information for the specified position
+" Pass optional arguments in the dictionary opt.
+" Currently, only one key/value is useful:
+"   - called_from_balloonexpr, this flag marks if we want the result from this
+"     ale#hover#Show to display in a balloon if possible
+"
+" Currently, the callbacks displays the info from hover :
+" - in the balloon if opt.called_from_balloonexpr and balloon_show is detected
+" - as status message otherwise
+function! ale#hover#Show(buffer, line, col, opt) abort
+    for l:linter in ale#linter#Get(getbufvar(a:buffer, '&filetype'))
         if !empty(l:linter.lsp)
-            call s:ShowDetails(l:linter)
+            call s:ShowDetails(l:linter, a:buffer, a:line, a:col, a:opt)
         endif
     endfor
 endfunction