Add initial support for workspace folders (#1265)

* add g:lsp_experimental_workspace_folders

* send client capabilities for workspaceFolders if g:lsp_experimental_workspace_folders is enabled

* fix g:lsp_experimental_workspace_folders missing s

* send workspaceFolders if workspaceFolder capability is defined via client

* add local copy add opened workspace folders

* Add support for workspace folders

* document Workspace folders

* add indent

* fix doc indent

autoload/lsp.vim

@@ -1,7 +1,8 @@
 let s:enabled = 0
 let s:already_setup = 0
 let s:Stream = lsp#callbag#makeSubject()
-let s:servers = {} " { lsp_id, server_info, init_callbacks, init_result, buffers: { path: { changed_tick } }
+" workspace_folders = { 'uri': { uri, name } }
+let s:servers = {} " { lsp_id, server_info, workspace_folders, init_callbacks, init_result, buffers: { path: { changed_tick } }
 let s:last_command_id = 0
 let s:notification_callbacks = [] " { name, callback }
 
@@ -167,10 +168,12 @@ function! lsp#register_server(server_info) abort
     if has_key(s:servers, l:server_name)
         call lsp#log('lsp#register_server', 'server already registered', l:server_name)
     endif
+    " NOTE: workspace_folders is dict for faster lookup instead of array
     let s:servers[l:server_name] = {
         \ 'server_info': a:server_info,
         \ 'lsp_id': 0,
         \ 'buffers': {},
+        \ 'workspace_folders': {},
         \ }
     call lsp#log('lsp#register_server', 'server registered', l:server_name)
     doautocmd <nomodeline> User lsp_register_server
@@ -565,7 +568,8 @@ function! lsp#default_get_supported_capabilities(server_info) abort
     \   },
     \   'workspace': {
     \       'applyEdit': v:true,
-    \       'configuration': v:true
+    \       'configuration': v:true,
+    \       'workspaceFolders': g:lsp_experimental_workspace_folders ? v:true : v:false,
     \   },
     \ }
 endfunction
@@ -598,6 +602,7 @@ function! s:ensure_init(buf, server_name, cb) abort
         let l:root_uri = lsp#utils#get_default_root_uri()
     endif
     let l:server['server_info']['_root_uri_resolved'] = l:root_uri
+    let l:server['workspace_folders'][l:root_uri] = { 'name': l:root_uri, 'uri': l:root_uri }
 
     if has_key(l:server_info, 'capabilities')
         let l:capabilities = l:server_info['capabilities']
@@ -616,6 +621,15 @@ function! s:ensure_init(buf, server_name, cb) abort
     \     'trace': 'off',
     \   },
     \ }
+    
+    let l:workspace_capabilities = get(l:capabilities, 'workspace', {})
+    if get(l:workspace_capabilities, 'workspaceFolders', v:false)
+        " TODO: extract folder name for l:root_uri
+        let l:server_info['workspaceFolders'] = [
+            \ { 'uri': l:root_uri, 'name': l:root_uri }
+            \ ]
+        let l:request['params']['workspaceFolders'] = l:server_info['workspaceFolders']
+    endif
 
     if has_key(l:server_info, 'initialization_options')
         let l:request.params['initializationOptions'] = l:server_info['initialization_options']
@@ -645,7 +659,6 @@ endfunction
 
 function! s:text_changes(buf, server_name) abort
     let l:sync_kind = lsp#capabilities#get_text_document_change_sync_kind(a:server_name)
-
     " When syncKind is None, return null for contentChanges.
     if l:sync_kind == 0
         return v:null
@@ -729,6 +742,10 @@ function! s:ensure_open(buf, server_name, cb) abort
         return
     endif
 
+    if lsp#capabilities#has_workspace_folders_change_notifications(a:server_name)
+        call s:workspace_add_folder(a:server_name)
+    endif
+
     call s:update_file_content(a:buf, a:server_name, lsp#utils#buffer#_get_lines(a:buf))
 
     let l:buffer_info = { 'changed_tick': getbufvar(a:buf, 'changedtick'), 'version': 1, 'uri': l:path }
@@ -748,6 +765,24 @@ function! s:ensure_open(buf, server_name, cb) abort
     call a:cb(l:msg)
 endfunction
 
+function! s:workspace_add_folder(server_name) abort
+    if !g:lsp_experimental_workspace_folders | return | endif
+    let l:server = s:servers[a:server_name]
+    let l:server_info = l:server['server_info']
+    let l:root_uri = has_key(l:server_info, 'root_uri') ?  l:server_info['root_uri'](l:server_info) : lsp#utils#get_default_root_uri()
+    if !has_key(l:server['workspace_folders'], l:root_uri)
+        let l:workspace_folder = { 'name': l:root_uri, 'uri': l:root_uri }
+        call lsp#log('adding workspace folder', a:server_name, l:workspace_folder)
+        call s:send_notification(a:server_name, {
+            \ 'method': 'workspace/didChangeWorkspaceFolders',
+            \ 'params': {
+            \    'added': [l:workspace_folder],
+            \  }
+            \ })
+        let l:server['workspace_folders'][l:root_uri] = l:workspace_folder
+    endif
+endfunction
+
 function! s:send_request(server_name, data) abort
     let l:lsp_id = s:servers[a:server_name]['lsp_id']
     let l:data = copy(a:data)
@@ -789,6 +824,7 @@ function! s:on_exit(server_name, id, data, event) abort
         if has_key(l:server, 'init_result')
             unlet l:server['init_result']
         endif
+        let l:server['workspace_folders'] = {}
         call lsp#stream(1, { 'server': '$vimlsp',
             \ 'response': { 'method': '$/vimlsp/lsp_server_exit', 'params': { 'server': a:server_name } } })
         doautocmd <nomodeline> User lsp_server_exit