feat(ui): ":%detach!" detaches all other UIs #39216

Problem:
Not easy for one UI to kick the others off a shared Nvim server.

Solution:
Treat `:%detach` as detach-other-UIs.

runtime/doc/api.txt

@@ -3863,6 +3863,20 @@ nvim_ui_try_resize_grid({grid}, {width}, {height})
       • {width}   (`integer`) The new requested width.
       • {height}  (`integer`) The new requested height.
 
+nvim__ui_detach({chan})                                    *nvim__ui_detach()*
+    WARNING: This feature is experimental/unstable.
+
+    Detaches the UI on channel `chan`.
+
+    Sets the channel's detach flag (so the server doesn't exit on stdio UIs),
+    sends an "error_exit" UI event, and closes the channel.
+
+    Attributes: ~
+        Since: 0.12.0
+
+    Parameters: ~
+      • {chan}  (`integer`) UI channel to disconnect.
+
 
 ==============================================================================
 Win_config Functions                                          *api-win_config*

runtime/doc/gui.txt

@@ -59,15 +59,21 @@ Use cases:
 ------------------------------------------------------------------------------
 Stop or detach the current UI
 
-                                                *:detach*
+                                      *:detach* *E5768*
-:detach
+:[range]detach
                 Detaches the current UI. Other UIs (if any) remain attached.
+                Fails with |E5768| if no UI is attached.
                 The server (typically `nvim --embed`) continues running as
                 a background process, and you can reattach to it later.
                 Before detaching, you may want to note the server address:
                 >vim
                     :echo v:servername
 <
+                When [range] covers the entire buffer (`%`, as in `:%detach`),
+                all other UIs are detached, keeping only the current one. The
+                command fails with |E16| for any other range. No-op if only
+                one UI is attached.
+
                 Note: The server closes the UI RPC channel, so :detach works
                 for any UI client. But if the client isn't expecting this, it
                 may (incorrectly) report an error.

runtime/doc/news.txt

@@ -223,6 +223,7 @@ EDITOR
 • |:restart| saves/restores the current session (window layout, buffers, …).
   • |:restart!| (with a bang "!") does not save/restore the session.
 • |ZR| restarts Nvim (|:restart|).
+• |:detach| with range "%" detaches all UIs except the current one.
 • |:uptime| displays uptime.
 • |:packupdate| and |:packdel| for managing |vim.pack|.
 • 'scrollback' is now also valid in |prompt-buffer| buffers to limit the

runtime/lua/vim/_core/server.lua

@@ -219,4 +219,24 @@ function M.ex_session_restart(eap, extra)
   end
 end
 
+--- Disconnects every UI except `keep_chan`, keeping the server running.
+---
+--- @param keep_chan integer Channel ID of the UI to preserve.
+--- @return integer # Number of UIs detached.
+function M.detach_others(keep_chan)
+  local uicount = #vim.api.nvim_list_uis()
+  for _, ui in ipairs(vim.api.nvim_list_uis()) do
+    if ui.chan and ui.chan ~= keep_chan then
+      vim.api.nvim__ui_detach(ui.chan)
+    end
+  end
+  local n = uicount - #vim.api.nvim_list_uis()
+  if n == 0 then
+    vim.api.nvim_echo({ { 'No other UIs are attached' } }, true, {})
+  else
+    vim.api.nvim_echo({ { ('Detached %d non-current UIs'):format(n) } }, true, {})
+  end
+  return n
+end
+
 return M

runtime/lua/vim/_meta/api.gen.lua

@@ -186,6 +186,16 @@ function vim.api.nvim__set_restart_on_crash(progpath, argv) end
 --- @return table<string,any> # Map of various internal stats.
 function vim.api.nvim__stats() end
 
+--- WARNING: This feature is experimental/unstable.
+---
+--- Detaches the UI on channel `chan`.
+---
+--- Sets the channel's detach flag (so the server doesn't exit on stdio UIs),
+--- sends an "error_exit" UI event, and closes the channel.
+---
+--- @param chan integer UI channel to disconnect.
+function vim.api.nvim__ui_detach(chan) end
+
 --- WARNING: This feature is experimental/unstable.
 ---
 --- @param str string

src/nvim/api/ui.c

@@ -17,6 +17,7 @@
 #include "nvim/autocmd_defs.h"
 #include "nvim/channel.h"
 #include "nvim/channel_defs.h"
+#include "nvim/errors.h"
 #include "nvim/eval/typval.h"
 #include "nvim/eval/vars.h"
 #include "nvim/event/defs.h"
@@ -40,6 +41,10 @@
 #include "nvim/types_defs.h"
 #include "nvim/ui.h"
 
+#ifdef MSWIN
+# include "nvim/os/os_win_console.h"
+#endif
+
 #define BUF_POS(ui) ((size_t)((ui)->packer.ptr - (ui)->packer.startptr))
 
 #include "api/ui.c.generated.h"
@@ -108,6 +113,36 @@ void remote_ui_disconnect(uint64_t channel_id, Error *err, bool send_error_exit)
   remote_ui_destroy(ui);
 }
 
+/// Detaches the UI on channel `chan`.
+///
+/// Sets the channel's detach flag (so the server doesn't exit on stdio UIs),
+/// sends an "error_exit" UI event, and closes the channel.
+///
+/// @param chan  UI channel to disconnect.
+/// @param[out] err Error details, if any.
+void nvim__ui_detach(Integer chan, Error *err)
+  FUNC_API_SINCE(14)
+{
+  Channel *c = find_channel((uint64_t)chan);
+  VALIDATE(c != NULL, "%s", e_invchan, {
+    return;
+  });
+#ifdef MSWIN
+  bool detach_stdio = c->streamtype == kChannelStreamStdio;
+#endif
+  c->detach = true;
+  remote_ui_disconnect((uint64_t)chan, err, true);
+  if (ERROR_SET(err)) {
+    return;
+  }
+  channel_close((uint64_t)chan, kChannelPartAll, NULL);
+#ifdef MSWIN
+  if (detach_stdio) {
+    os_swap_to_hidden_console();
+  }
+#endif
+}
+
 #ifdef EXITFREE
 void remote_ui_free_all_mem(void)
 {

src/nvim/errors.h

@@ -164,6 +164,7 @@ EXTERN const char e_auabort[] INIT(= N_("E855: Autocommands caused command to ab
 EXTERN const char e_api_error[] INIT(= N_("E5555: API call: %s"));
 
 EXTERN const char e_fast_api_disabled[] INIT(= N_("E5560: %s must not be called in a fast event context"));
+EXTERN const char e_noui[] INIT(= N_("E5768: No UI attached"));
 
 EXTERN const char e_floatonly[] INIT(= N_("E5601: Cannot close window, only floating window would remain"));
 EXTERN const char e_floatexchange[] INIT(= N_("E5602: Cannot exchange or rotate float"));

src/nvim/ex_cmds.lua

@@ -742,8 +742,8 @@ M.cmds = {
   },
   {
     command = 'detach',
-    flags = TRLBAR,
+    flags = bit.bor(RANGE, TRLBAR),
-    addr_type = 'ADDR_NONE',
+    addr_type = 'ADDR_OTHER',
     func = 'ex_detach',
   },
   {

src/nvim/ex_docmd.c

@@ -5961,22 +5961,36 @@ static void ex_tabs(exarg_T *eap)
 ///
 /// Detaches the current UI.
 ///
-/// ":detach!" with bang (!) detaches all UIs _except_ the current UI.
+/// ":%detach" detaches all UIs _except_ the current UI.
 static void ex_detach(exarg_T *eap)
 {
   // come on pooky let's burn this mf down
-  if (eap && eap->forceit) {
+  if (!current_ui) {
-    emsg("bang (!) not supported yet");
+    emsg(_(e_noui));
+    return;
+  }
+
+  if (eap && eap->addr_count > 0) {
+    if (eap->line1 != 1 || eap->line2 != curbuf->b_ml.ml_line_count) {
+      emsg(_(e_invrange));
+      return;
+    }
+
+    typval_T lua_args[] = {
+      { .v_type = VAR_NUMBER, .vval.v_number = (varnumber_T)current_ui },
+      { .v_type = VAR_UNKNOWN },
+    };
+    typval_T rv = TV_INITIAL_VALUE;
+    nlua_call_typval("vim._core.server", "detach_others", lua_args, &rv);
+    ILOG("%%detach current_ui=%" PRIu64 " detached=%zu", current_ui,
+         (rv.v_type == VAR_NUMBER && rv.vval.v_number > 0)
+         ? (size_t)rv.vval.v_number : (size_t)0);
+    tv_clear(&rv);
   } else {
     // 1. Send "error_exit" UI-event (notification only).
     // 2. Perform server-side UI detach.
     // 3. Close server-side channel without self-exit.
 
-    if (!current_ui) {
-      emsg("UI not attached");
-      return;
-    }
-
     Channel *chan = find_channel(current_ui);
     if (!chan) {
       emsg(e_invchan);

test/functional/core/main_spec.lua

@@ -193,7 +193,7 @@ describe('vim._core', function()
 
     -- All `vim._core.*` modules are builtin.
     t.eq(
-      { 'ex_session_restart', 'rebind_after_restart', 'serverlist' },
+      { 'detach_others', 'ex_session_restart', 'rebind_after_restart', 'serverlist' },
       n.exec_lua([[local k = vim.tbl_keys(require('vim._core.server')); table.sort(k); return k]])
     )
     local expected = {

test/functional/terminal/tui_spec.lua

@@ -149,14 +149,16 @@ describe('TUI', function()
 end)
 
 describe('TUI :detach', function()
-  it('does not stop server', function()
+  local child_server, screen
+
+  local function setup_detach_child()
     n.clear()
     finally(function()
       n.check_close()
     end)
 
-    local child_server = new_pipename()
+    child_server = new_pipename()
-    local screen = tt.setup_child_nvim({
+    screen = tt.setup_child_nvim({
       '--listen',
       child_server,
       '-u',
@@ -169,6 +171,10 @@ describe('TUI :detach', function()
       nvim_set .. ' laststatus=2 background=dark',
     }, { env = env_notermguicolors })
     tt.override_screen_expect_for_conpty(screen)
+  end
+
+  it('does not stop server', function()
+    setup_detach_child()
 
     tt.feed_data('iHello, World')
     screen:expect([[
@@ -193,8 +199,8 @@ describe('TUI :detach', function()
       { child_session:request('nvim_command', 'detach!') }
     )
     eq(
-      { false, { 0, 'Vim(detach):E481: No range allowed: 1detach' } },
+      { false, { 0, 'Vim(detach):E16: Invalid range' } },
-      { child_session:request('nvim_command', '1detach') }
+      { child_session:request('nvim_command', '2detach') }
     )
     eq(
       { false, { 0, 'Vim(detach):E488: Trailing characters: foo: detach foo' } },
@@ -234,6 +240,72 @@ describe('TUI :detach', function()
       {5:-- TERMINAL --}                                    |
     ]])
   end)
+
+  it('% detaches other UIs', function()
+    setup_detach_child()
+    finally(function()
+      pcall(function()
+        local s = n.connect(child_server)
+        s:request('nvim_command', 'qall!')
+      end)
+    end)
+
+    tt.feed_data('iHello from detach!')
+    screen:expect({ any = vim.pesc('Hello from detach!^') })
+    tt.feed_data('\027')
+
+    local child_session = n.connect(child_server)
+    local _, uis_before = child_session:request('nvim_list_uis')
+    eq(1, #uis_before)
+    local tui_chan_id = uis_before[1].chan
+
+    -- :%detach with only 1 UI is a no-op.
+    tt.feed_data(':%detach\013')
+    screen:expect({ any = vim.pesc('No other UIs are attached') })
+    local _, uis_noop = child_session:request('nvim_list_uis')
+    eq(1, #uis_noop)
+
+    child_session:request('nvim_ui_attach', 50, 7, {})
+    local _, uis_attached = child_session:request('nvim_list_uis')
+    eq(2, #uis_attached)
+
+    tt.feed_data(':%detach\013')
+    screen:expect([[
+      Hello from detach^!                                |
+      {100:~                                                 }|*3
+      {3:[No Name] [+]                                     }|
+                                                        |
+      {5:-- TERMINAL --}                                    |
+    ]])
+
+    local verify_session = n.connect(child_server)
+    local _, uis_after = verify_session:request('nvim_list_uis')
+    eq(1, #uis_after)
+    eq(tui_chan_id, uis_after[1].chan)
+  end)
+
+  it('% detaches the original UI when invoked from a later UI', function()
+    setup_detach_child()
+    finally(function()
+      pcall(function()
+        local s = n.connect(child_server)
+        s:request('nvim_command', 'qall!')
+      end)
+    end)
+
+    screen:expect({ any = vim.pesc('[No Name]') })
+    local child_session = n.connect(child_server)
+    child_session:request('nvim_ui_attach', 50, 7, {})
+    local _, uis_before = child_session:request('nvim_list_uis')
+    eq(2, #uis_before)
+
+    eq({ true, vim.NIL }, { child_session:request('nvim_command', '%detach') })
+    screen:expect({ any = [[Process exited 0]] })
+
+    local status, uis_after = child_session:request('nvim_list_uis')
+    ok(status)
+    eq(1, #uis_after)
+  end)
 end)
 
 describe('TUI :restart', function()