Add support for diagnostics display funcref for more flexible integration

autoload/LanguageClient.vim

@@ -117,6 +117,14 @@ function! s:hasSnippetSupport() abort
     return 0
 endfunction
 
+function! s:getStringOrFuncref(name, default) abort
+  if type(get(g:, a:name, a:default)) is s:TYPE.funcref
+    return string(get(g:, a:name, a:default))
+  else
+    return get(g:, a:name, a:default)
+  endif
+endfunction
+
 function! s:getSelectionUI() abort
 	if type(get(g:, 'LanguageClient_selectionUI', v:null)) is s:TYPE.funcref
 		return 'funcref'
@@ -1236,11 +1244,11 @@ function! LanguageClient#handleVimLeavePre() abort
     endtry
 endfunction
 
-function! s:LanguageClient_FZFSinkLocation(line) abort
+function! g:LanguageClient_FZFSinkLocation(line) abort
     return LanguageClient#Notify('LanguageClient_FZFSinkLocation', [a:line])
 endfunction
 
-function! LanguageClient_FZFSinkCommand(selection) abort
+function! g:LanguageClient_FZFSinkCommand(selection) abort
     return LanguageClient#Notify('LanguageClient_FZFSinkCommand', {
                 \ 'selection': a:selection,
                 \ })

doc/LanguageClient.txt

@@ -207,7 +207,49 @@ Valid options: "off" | "messages" | "verbose"
 List used to fill diagnostic messages.
 
 Default: "Quickfix"
-Valid options: "Quickfix" | "Location" | "Disabled"
+Valid options: "Quickfix" | "Location" | "Disabled" | |Funcref|
+
+If you use a |Funcref|, the referenced function should have two arguments
+(filename, diagnostics). filename is the name of the file of which the
+diagnostics correspond to, and diagnostics is the list of diagnostics for said
+file. Those diagnostics are as specified in the LSP specification.
+
+For example, if you wanted to use `dense-analysis/ale` to display diagnostics
+instead of this plugin you could use something like this:
+
+```
+function! DisplayDiagnostics(filename, diagnostics) abort
+  let s:diagnostics = []
+
+  for d in a:diagnostics
+    let s:severity = 'I'
+    if d.severity == 1
+      let s:severity = 'E'
+    elseif d.severity == 2
+      let s:severity = 'W'
+    endif
+
+    call add(s:diagnostics, {
+      \ "filename": a:filename,
+      \ "text": d.message,
+      \ "lnum": d.range.start.line + 1,
+      \ "end_lnum": d.range.end.line + 1,
+      \ "col": d.range.end.character,
+      \ "end_col": d.range.end.character,
+      \ "type": s:severity,
+      \ })
+  endfor
+
+  call ale#other_source#ShowResults(bufnr('%'), 'LanguageClientNeovim', s:diagnostics)
+endfunction
+
+let g:LanguageClient_diagnosticsDisplayFuncref = function('DisplayDiagnostics')
+```
+
+Keep in mind that to complete the integration between `ale` and
+`LanguageClient-neovim` you need to add `LanguageClientNeovim` (or the name of
+the linter you used in the call to ShowResults) to the list of linters to be
+used in `ale`.
 
 2.10 g:LanguageClient_diagnosticsEnable    *g:LanguageClient_diagnosticsEnable*