Fix 4141 - Stop press enter prompt on long diagnostic messages (#4144)

* Fix 4141 - Stop press enter prompt on long diagnostic messages

* Fix 4139 - Check for array before join truncated_echo

autoload/ale/cursor.vim

@@ -11,9 +11,9 @@ let g:ale_echo_msg_format = get(g:, 'ale_echo_msg_format', '%code: %%s')
 let s:cursor_timer = -1
 
 " A wrapper for echon so we can test messages we echo in Vader tests.
-function! ale#cursor#Echon(message) abort
+function! ale#cursor#Echom(message) abort
     " no-custom-checks
-    echon a:message
+    exec "norm! :echom a:message\n"
 endfunction
 
 function! ale#cursor#TruncatedEcho(original_message) abort
@@ -36,14 +36,7 @@ function! ale#cursor#TruncatedEcho(original_message) abort
         silent! setlocal shortmess+=T
 
         try
-            " echon will not display the message if it exceeds the width of
-            " the window
-            if &columns < strdisplaywidth(l:message)
-                " Truncate message longer than window width with trailing '...'
-                let l:message = l:message[:&columns - 5] . '...'
-            endif
-
-            call ale#cursor#Echon(l:message)
+            call ale#cursor#Echom(l:message)
         catch /^Vim\%((\a\+)\)\=:E523/
             " Fallback into manual truncate (#1987)
             let l:winwidth = winwidth(0)

autoload/ale/hover.vim

@@ -231,7 +231,11 @@ function! ale#hover#HandleLSPResponse(conn_id, response) abort
             \&& (l:set_balloons is 1 || l:set_balloons is# 'hover')
                 call balloon_show(join(l:lines, "\n"))
             elseif get(l:options, 'truncated_echo', 0)
-                call ale#cursor#TruncatedEcho(join(l:lines[0], '\n'))
+                if type(l:lines[0]) is# v:t_list
+                    call ale#cursor#TruncatedEcho(join(l:lines[0], '\n'))
+                else
+                    call ale#cursor#TruncatedEcho(l:lines[0])
+                endif
             elseif g:ale_hover_to_floating_preview || g:ale_floating_preview
                 call ale#floating_preview#Show(l:lines, {
                 \   'filetype': 'ale-preview.message',

test/test_cursor_warnings.vader

@@ -89,7 +89,7 @@ Before:
 
   let g:last_message = ''
 
-  function! ale#cursor#Echon(message) abort
+  function! ale#cursor#Echom(message) abort
     let g:last_message = a:message
   endfunction