Add a way to preconfigure callbacks for lang servers

autoload/langserver/default.vim

@@ -1,4 +1,6 @@
-let s:langserver_executabe = 'langserver-go'
+let s:preconfigured_location = expand('<sfile>:h') . '/../../preconfigured/'
+let s:callbacks_name = '/callbacks.vim'
+
 
 ""
 " Get the default command for starting the server
@@ -30,3 +32,23 @@ function! langserver#default#cmd(...) abort
   echoerr 'Please consult the documentation for how to configure the langserver'
   return l:bad_cmd
 endfunction
+
+function! langserver#default#extension_callbacks(...) abort
+  if a:0 > 0
+    let l:filetype_key = langserver#util#get_executable_key(a:1)
+  else
+    let l:filetype_key = langserver#util#get_executable_key(&filetype)
+  endif
+
+  if has_key(g:langserver_executables, l:filetype_key)
+    let l:location = s:preconfigured_location . g:langserver_executables[l:filetype_key]['name']
+    let l:file_to_source = l:location . s:callbacks_name
+    if isdirectory(l:location) && filereadable(l:file_to_source)
+      execute('source ' . l:file_to_source)
+      let l:subbed = substitute(g:langserver_executables[l:filetype_key]['name'], '/', '_', 'g')
+      return Preconfigured_{l:subbed}()
+    else
+      return {}
+    endif
+  endif
+endfunction

preconfigured/freebroccolo/ocaml-language-server/callbacks.vim

@@ -0,0 +1,20 @@
+function! s:give_word_at_position(context) abort
+  "  'params': 
+  "      {'uri': 'file:///home/tj/Downloads/example-ocaml-merlin/src/main.ml',
+  "      'position': {'character': 9, 'line': 6}
+  "      }
+  if !has_key(a:context, 'uri') || !has_key(a:context, 'position')
+    " TODO: Log an error?
+    return
+  endif
+
+  let l:loc_bufnr = bufnr(langserver#util#get_filename(langserver#util#get_lsp_id(), a:context.uri))
+  let l:loc_line = langserver#util#get_line(l:loc_bufnr, a:context.uri, a.position.line - 1)
+
+  call langserver#log#log('error', 'LOC LINE: ' . l:loc_line, v:true)
+endfunction
+
+
+let s:register_callbacks = {
+      \ 'reason.client.giveWordAtPosition': function('s:give_word_at_position'),
+      \ }

preconfigured/test/test/callbacks.vim

@@ -0,0 +1,9 @@
+function! s:test_function(context) abort
+  return 'tested ' . a:context['var'] . '!' 
+endfunction
+
+function! Preconfigured_test_test() abort
+  return {
+        \ 'method_name': function('s:test_function'),
+        \ }
+endfunction

tests/test_defaults.vader

@@ -53,7 +53,7 @@ Execute (Testing executable function as cmd with cs list):
 
   let g:langserver_executables = {
         \ 'example,this,that,the_other': {
-              \ 'name': 'sourcegraph/langserver-go',
+              \ 'name': 'this/langserver',
               \ 'cmd': function('s:set_global_var'),
               \ },
         \ }
@@ -63,4 +63,22 @@ Execute (Testing executable function as cmd with cs list):
 
   let g:langserver_executables = g:__temp_exec
 
+Execute (Getting predefined settings):
+  " Pass
+
+Execute (Getting predefined functions and passing args):
+  let g:__temp_exec = get(g:, 'langserver_executables', {})
+
+  let g:langserver_executables = {
+        \ 'testing': {
+              \ 'name': 'test/test',
+              \ 'cmd': ['echo', '"hello"'],
+              \ },
+        \ }
+
+  let test_functions = langserver#default#extension_callbacks('testing')
+  AssertEqual 'tested foo!', call(test_functions['method_name'], [{'var': 'foo'}])
+
+  let g:langserver_executables = g:__temp_exec
+