Add formatting_seq_sync, change formatting and formatting_sync

runtime/lua/vim/lsp/buf.lua

@@ -111,6 +111,39 @@ function M.completion(context)
   return request('textDocument/completion', params)
 end
 
+--@private
+--- If there is more than one client with formatting capability, asks the user
+--- which one to use.
+--
+--@returns The client to use for formatting
+local function get_formatting_client()
+  local clients = vim.tbl_values(vim.lsp.buf_get_clients());
+  clients = vim.tbl_filter(function (client)
+    return client.resolved_capabilities.document_formatting
+  end, clients)
+  -- better UX when choices are always in the same order (between restarts)
+  table.sort(clients, function (a, b) return a.name < b.name end)
+
+  if #clients > 1 then
+    local choices = {}
+    for k,v in ipairs(clients) do
+      table.insert(choices, string.format("%d %s", k, v.name))
+    end
+    local user_choice = vim.fn.confirm(
+      "Select a language server for formatting:",
+      table.concat(choices, "\n"),
+      0,
+      "Question"
+    )
+    if user_choice == 0 then return nil end
+    return clients[user_choice]
+  elseif #clients < 1 then
+    return nil
+  else
+    return clients[1]
+  end
+end
+
 --- Formats the current buffer.
 ---
 --@param options (optional, table) Can be used to specify FormattingOptions.
@@ -119,8 +152,11 @@ end
 --
 --@see https://microsoft.github.io/language-server-protocol/specification#textDocument_formatting
 function M.formatting(options)
+  local client = get_formatting_client()
+  if client == nil then return end
+
   local params = util.make_formatting_params(options)
-  return request('textDocument/formatting', params)
+  return client.request("textDocument/formatting", params)
 end
 
 --- Performs |vim.lsp.buf.formatting()| synchronously.
@@ -134,14 +170,58 @@ end
 ---
 --@param options Table with valid `FormattingOptions` entries
 --@param timeout_ms (number) Request timeout
+--@see |vim.lsp.buf.formatting_seq_sync|
 function M.formatting_sync(options, timeout_ms)
+  local client = get_formatting_client()
+  if client == nil then return end
+
   local params = util.make_formatting_params(options)
-  local result = vim.lsp.buf_request_sync(0, "textDocument/formatting", params, timeout_ms)
-  if not result or vim.tbl_isempty(result) then return end
-  local _, formatting_result = next(result)
-  result = formatting_result.result
-  if not result then return end
-  vim.lsp.util.apply_text_edits(result)
+  local result = client.request_sync("textDocument/formatting", params, timeout_ms)
+  if result and result.result then
+    util.apply_text_edits(result.result)
+  end
+end
+
+--- Formats the current buffer by sequentially requesting formatting from attached clients.
+---
+--- Useful when multiple clients with formatting capability are attached.
+---
+--- Since it's synchronous, can be used for running on save, to make sure buffer is formatted
+--- prior to being saved. {timeout_ms} is passed on to the |vim.lsp.client| `request_sync` method.
+--- Example:
+--- <pre>
+--- vim.api.nvim_command[[autocmd BufWritePre <buffer> lua vim.lsp.buf.formatting_seq_sync()]]
+--- </pre>
+---
+--@param options (optional, table) `FormattingOptions` entries
+--@param timeout_ms (optional, number) Request timeout
+--@param order (optional, table) List of client names. Formatting is requested from clients
+---in the following order: first all clients that are not in the `order` list, then
+---the remaining clients in the order as they occur in the `order` list.
+function M.formatting_seq_sync(options, timeout_ms, order)
+  local clients = vim.tbl_values(vim.lsp.buf_get_clients());
+
+  -- sort the clients according to `order`
+  for _, client_name in ipairs(order or {}) do
+    -- if the client exists, move to the end of the list
+    for i, client in ipairs(clients) do
+      if client.name == client_name then
+        table.insert(clients, table.remove(clients, i))
+        break
+      end
+    end
+  end
+
+  -- loop through the clients and make synchronous formatting requests
+  for _, client in ipairs(clients) do
+    if client.resolved_capabilities.document_formatting then
+      local params = util.make_formatting_params(options)
+      local result = client.request_sync("textDocument/formatting", params, timeout_ms)
+      if result and result.result then
+        util.apply_text_edits(result.result)
+      end
+    end
+  end
 end
 
 --- Formats a given range.