feat(ui): :connect command #34586

Add the `:connect <address>` command which connects the currently
running TUI to the server at the given address.

runtime/doc/gui.txt

@@ -87,6 +87,22 @@ Restart Nvim
                 event, this command is equivalent to `:qall`.
                 Note: Only works if the UI and server are on the same system.
 
+------------------------------------------------------------------------------
+Connect UI to a different server
+
+                                                *:connect*
+
+:connect {address}
+                Detaches the UI from the server it is currently attached to
+                and attaches it to the server at {address} instead.
+
+                Note: If the current UI hasn't implemented the "connect" UI
+                event, this command is equivalent to |:detach|.
+
+:connect! {address}
+                Same as |:connect| but it also stops the detached server if
+                no other UI is currently attached to it.
+
 ------------------------------------------------------------------------------
 GUI commands
 

runtime/doc/news.txt

@@ -297,6 +297,8 @@ TUI
 UI
 
 • |:restart| restarts Nvim and reattaches the current UI.
+• |:connect| dynamically connects the current UI to the server at the given
+  address.
 • |:checkhealth| shows a summary in the header for every healthcheck.
 • |ui-multigrid| provides composition information and absolute coordinates.
 • `vim._extui` provides an experimental commandline and message UI intended to

src/nvim/api/ui.c

@@ -319,6 +319,20 @@ bool remote_ui_restart(uint64_t channel_id, Error *err)
   return true;
 }
 
+// Send a connect UI event to the UI on the given channel
+void remote_ui_connect(uint64_t channel_id, char *server_addr, Error *err)
+{
+  RemoteUI *ui = get_ui_or_err(channel_id, err);
+  if (!ui) {
+    return;
+  }
+
+  MAXSIZE_TEMP_ARRAY(args, 1);
+  ADD_C(args, CSTR_AS_OBJ(server_addr));
+
+  push_call(ui, "connect", args);
+}
+
 // TODO(bfredl): use me to detach a specific ui from the server
 void remote_ui_stop(RemoteUI *ui)
 {

src/nvim/api/ui_events.in.h

@@ -27,6 +27,8 @@ void visual_bell(void)
   FUNC_API_SINCE(3);
 void flush(void)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL;
+void connect(Array args)
+  FUNC_API_SINCE(14) FUNC_API_REMOTE_ONLY FUNC_API_REMOTE_IMPL FUNC_API_CLIENT_IMPL;
 void restart(String progpath, Array argv)
   FUNC_API_SINCE(14) FUNC_API_REMOTE_ONLY FUNC_API_REMOTE_IMPL FUNC_API_CLIENT_IMPL;
 void suspend(void)

src/nvim/event/stream.c

@@ -146,7 +146,7 @@ void stream_close_handle(Stream *stream, bool rstream)
 static void rstream_close_cb(uv_handle_t *handle)
 {
   RStream *stream = handle->data;
-  if (stream->buffer) {
+  if (stream && stream->buffer) {
     free_block(stream->buffer);
   }
   close_cb(handle);
@@ -155,10 +155,10 @@ static void rstream_close_cb(uv_handle_t *handle)
 static void close_cb(uv_handle_t *handle)
 {
   Stream *stream = handle->data;
-  if (stream->close_cb) {
+  if (stream && stream->close_cb) {
     stream->close_cb(stream, stream->close_cb_data);
   }
-  if (stream->internal_close_cb) {
+  if (stream && stream->internal_close_cb) {
     stream->internal_close_cb(stream, stream->internal_data);
   }
 }

src/nvim/ex_cmds.lua

@@ -582,6 +582,12 @@ M.cmds = {
     addr_type = 'ADDR_OTHER',
     func = 'ex_menu',
   },
+  {
+    command = 'connect',
+    flags = bit.bor(BANG, WORD1, NOTRLCOM, NEEDARG),
+    addr_type = 'ADDR_NONE',
+    func = 'ex_connect',
+  },
   {
     command = 'copy',
     flags = bit.bor(RANGE, WHOLEFOLD, EXTRA, TRLBAR, CMDWIN, LOCK_OK, MODIFY),

src/nvim/ex_docmd.c

@@ -5649,6 +5649,32 @@ static void ex_detach(exarg_T *eap)
   }
 }
 
+/// ":connect"
+///
+/// Connects the current UI to a different server
+///
+/// ":connect <address>" detaches the current UI and connects to the given server.
+/// ":connect! <address>" stops the current server if no other UIs are attached, then connects to the given server.
+static void ex_connect(exarg_T *eap)
+{
+  bool stop_server = eap->forceit ? (ui_active() == 1) : false;
+
+  Error err = ERROR_INIT;
+  remote_ui_connect(current_ui, eap->arg, &err);
+
+  if (ERROR_SET(&err)) {
+    emsg(err.msg);
+    api_clear_error(&err);
+    return;
+  }
+
+  ex_detach(NULL);
+  if (stop_server) {
+    exiting = true;
+    getout(0);
+  }
+}
+
 /// ":mode":
 /// If no argument given, get the screen size and redraw.
 static void ex_mode(exarg_T *eap)

src/nvim/ui_client.c

@@ -281,6 +281,38 @@ void ui_client_event_raw_line(GridLineEvent *g)
                (const schar_T *)grid_line_buf_char, grid_line_buf_attr);
 }
 
+void ui_client_event_connect(Array args)
+{
+  if (args.size < 1 || args.items[0].type != kObjectTypeString) {
+    ELOG("Error handling UI event 'connect'");
+    return;
+  }
+
+  char *server_addr = args.items[0].data.string.data;
+  multiqueue_put(main_loop.fast_events, channel_connect_event, server_addr);
+}
+
+static void channel_connect_event(void **argv)
+{
+  char *server_addr = argv[0];
+
+  const char *err = "";
+  bool is_tcp = !!strrchr(server_addr, ':');
+  CallbackReader on_data = CALLBACK_READER_INIT;
+  uint64_t chan = channel_connect(is_tcp, server_addr, true, on_data, 50, &err);
+
+  if (!strequal(err, "")) {
+    ELOG("Error handling UI event 'connect': %s", err);
+    return;
+  }
+
+  ui_client_channel_id = chan;
+  ui_client_is_remote = true;
+  ui_client_attach(tui_width, tui_height, tui_term, tui_rgb);
+
+  ELOG("Connected to channel: %" PRId64, chan);
+}
+
 /// When a "restart" UI event is received, its arguments are saved here when
 /// waiting for the server to exit.
 static Array restart_args = ARRAY_DICT_INIT;

test/functional/terminal/tui_spec.lua

@@ -365,6 +365,123 @@ describe('TUI :restart', function()
   end)
 end)
 
+describe('TUI :connect', function()
+  if t.skip(is_os('win'), "relies on :detach which currently doesn't work on windows") then
+    return
+  end
+
+  it('leaves the current server running', function()
+    n.clear()
+    finally(function()
+      n.check_close()
+    end)
+
+    local server1 = new_pipename()
+    local screen = tt.setup_child_nvim({
+      '--listen',
+      server1,
+      '-u',
+      'NONE',
+    })
+
+    tt.feed_data(':connect\013')
+    screen:expect([[
+      ^                                                  |
+      ~                                                 |*3
+      [No Name]                       0,0-1          All|
+      E471: Argument required                           |
+      {5:-- TERMINAL --}                                    |
+    ]])
+
+    screen:detach()
+
+    local server2 = new_pipename()
+    local screen2 = tt.setup_child_nvim({
+      '--listen',
+      server2,
+      '-u',
+      'NONE',
+    })
+    tt.feed_data('iThis is server 2.\027')
+    tt.feed_data(':connect ' .. server1 .. '\013')
+
+    screen2:expect({
+      any = [[Process exited]],
+    })
+
+    local server1_session = n.connect(server1)
+    server1_session:request('nvim_command', 'qall!')
+
+    screen2:detach()
+
+    local server2_session = n.connect(server2)
+
+    local screen3 = tt.setup_child_nvim({
+      '--remote-ui',
+      '--server',
+      server2,
+    })
+    screen3:expect([[
+      This is server 2^.                                 |
+      ~                                                 |*3
+      {2:[No Name] [+]                   1,17           All}|
+                                                        |
+      {5:-- TERMINAL --}                                    |
+    ]])
+
+    screen3:detach()
+    server2_session:request('nvim_command', 'qall!')
+  end)
+  it('! stops the current server', function()
+    n.clear()
+    finally(function()
+      n.check_close()
+    end)
+
+    local server1 = new_pipename()
+    local screen1 = tt.setup_child_nvim({
+      '--listen',
+      server1,
+    })
+    tt.feed_data('iThis is server 1')
+
+    screen1:detach()
+
+    local server2 = new_pipename()
+    local screen2 = tt.setup_child_nvim({
+      '--listen',
+      server2,
+    })
+    tt.feed_data('\027:connect! ' .. server1 .. '\013')
+    screen2:expect([[
+      This is server 1^                                  |
+      ~                                                 |*3
+      [No Name] [+]                   1,17           All|
+      -- INSERT --                                      |
+      {5:-- TERMINAL --}                                    |
+    ]])
+
+    local server1_session = n.connect(server1)
+    server1_session:request('nvim_command', 'qall!')
+
+    screen2:detach()
+
+    local screen3 = tt.setup_child_nvim({
+      '--remote-ui',
+      '--server',
+      server2,
+    })
+    screen3:expect([[
+      Remote ui failed to start: connection refused     |
+                                                        |
+      [Process exited 1]^                                |
+                                                        |*3
+      {5:-- TERMINAL --}                                    |
+    ]])
+    screen3:detach()
+  end)
+end)
+
 if t.skip(is_os('win')) then
   return
 end