feat(tui): builtin UI (TUI) sets client info #30397

Problem:
The default builtin UI client does not declare its client info. This
reduces discoverability and makes it difficult for plugins to identify
the UI.

Solution:
- Call nvim_set_client_info after attaching, as recommended by `:help dev-ui`.
- Also set the "pid" field.
- Also change `ui_active()` to return a count. Not directly relevant to
  this commit, but will be useful later.

13 files changed, 164 insertions, 44 deletions

diff --git a/runtime/doc/api.txt b/runtime/doc/api.txt
index a7b59f20bc..45c6168e3d 100644
--- a/runtime/doc/api.txt
+++ b/runtime/doc/api.txt
@@ -779,7 +779,7 @@ nvim_get_chan_info({chan})                              *nvim_get_chan_info()*
       • {chan}  channel_id, or 0 for current channel
 
     Return: ~
-        Dictionary describing a channel, with these keys:
+        Channel info dict with these keys:
         • "id" Channel id.
         • "argv" (optional) Job arguments list.
         • "stream" Stream underlying the channel.
@@ -792,11 +792,11 @@ nvim_get_chan_info({chan})                              *nvim_get_chan_info()*
           • "terminal" |terminal| instance interprets ASCII sequences.
           • "rpc" |RPC| communication on the channel is active.
         • "pty" (optional) Name of pseudoterminal. On a POSIX system this is a
-          device path like "/dev/pts/1". If the name is unknown, the key will
-          still be present if a pty is used (e.g. for conpty on Windows).
-        • "buffer" (optional) Buffer with connected |terminal| instance.
+          device path like "/dev/pts/1". If unknown, the key will still be
+          present if a pty is used (e.g. for conpty on Windows).
+        • "buffer" (optional) Buffer connected to |terminal| instance.
         • "client" (optional) Info about the peer (client on the other end of
-          the RPC channel), if provided by it via |nvim_set_client_info()|.
+          the RPC channel), which it provided via |nvim_set_client_info()|.
 
 nvim_get_color_by_name({name})                      *nvim_get_color_by_name()*
     Returns the 24-bit RGB value of a |nvim_get_color_map()| color name or
@@ -1285,6 +1285,7 @@ nvim_set_client_info({name}, {version}, {type}, {methods}, {attributes})
                         inclusive.
       • {attributes}  Arbitrary string:string map of informal client
                       properties. Suggested keys:
+                      • "pid": Process id.
                       • "website": Client homepage URL (e.g. GitHub
                         repository)
                       • "license": License description ("Apache 2", "GPLv3",
diff --git a/runtime/doc/gui.txt b/runtime/doc/gui.txt
index 69e251e657..f0f2334ff6 100644
--- a/runtime/doc/gui.txt
+++ b/runtime/doc/gui.txt
@@ -6,14 +6,38 @@
 
 Nvim Graphical User Interface				*gui* *GUI*
 
+Any client that supports the Nvim |ui-protocol| can be used as a UI for Nvim.
+And multiple UIs can connect to the same Nvim instance! The terms "UI" and
+"GUI" are often used interchangeably because all Nvim UI clients have the same
+potential capabilities; the "TUI" refers to a UI client that outputs to your
+terminal, whereas a "GUI" outputs directly to the OS graphics system.
+
+Except where noted, this document describes UI capabilities available to both
+TUI and GUI (assuming the UI supports the given feature). See |TUI| for notes
+specific to the terminal UI. Help tags with the "gui-" prefix refer to UI
+features, whereas help tags with the "ui-" prefix refer to the |ui-protocol|.
+
+Nvim provides a default, builtin UI (the |TUI|), but there are many other
+(third-party) GUIs that you can use instead:
+
+- Firenvim (Nvim in your web browser!) https://github.com/glacambre/firenvim
+- vscode-neovim (Nvim in VSCode!) https://github.com/vscode-neovim/vscode-neovim
+- Neovide https://neovide.dev/
+- Goneovim https://github.com/akiyosi/goneovim
+- Nvy https://github.com/RMichelsen/Nvy
+- Neovim-Qt (Qt5) https://github.com/equalsraf/neovim-qt
+- VimR (macOS) https://github.com/qvacua/vimr
+- Others https://github.com/neovim/neovim/wiki/Related-projects#gui
+
                                       Type |gO| to see the table of contents.
 
 ==============================================================================
-Starting the GUI				*gui-start* *E229* *E233*
+Starting the GUI				*gui-config* *gui-start*
 
 				*ginit.vim* *gui-init* *gvimrc* *$MYGVIMRC*
 For GUI-specific configuration Nvim provides the |UIEnter| event.  This
-happens after other |initialization|s, like reading your vimrc file.
+happens after other |initialization|s, or whenever a UI attaches (multiple UIs
+can connect to any Nvim instance).
 
 Example: this sets "g:gui" to the value of the UI's "rgb" field:    >
 	:autocmd UIEnter * let g:gui = filter(nvim_list_uis(),{k,v-> v.chan==v:event.chan})[0].rgb
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index 515aef753d..1d95886356 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -189,6 +189,9 @@ TREESITTER
 
 TUI
 
+• The builtin UI declares info |nvim_set_client_info()| on its channel. See
+  |startup-tui|. To see the current UI info, try this: >
+    :lua =vim.api.nvim_get_chan_info(vim.api.nvim_list_uis()[1].chan)
 • |log| messages written by the builtin UI client (TUI, |--remote-ui|) are
   now prefixed with "ui" instead of "?".
 
diff --git a/runtime/doc/tui.txt b/runtime/doc/tui.txt
index d2af878239..9493f91b1e 100644
--- a/runtime/doc/tui.txt
+++ b/runtime/doc/tui.txt
@@ -6,28 +6,45 @@
 
 Terminal UI						*TUI* *tui*
 
-Nvim uses a list of terminal capabilities to display its user interface
-(except in |--embed| and |--headless| modes). If that information is wrong,
-the screen may be messed up or keys may not be recognized.
+By default when you run `nvim` (without |--embed| or |--headless|) it starts
+the builtin "terminal UI" (TUI). This default UI is optional: you can run Nvim
+as a "headless" server, or you can use a |GUI|.
 
                                       Type |gO| to see the table of contents.
 
 ==============================================================================
-Startup						*startup-terminal*
+Startup					*startup-tui* *startup-terminal*
+
+Nvim has a client-server architecture: by default when you run `nvim`, this
+starts the builtin UI client, which starts a `nvim --embed` server (child)
+process that the UI client connects to. After attaching to the server, the UI
+client calls |nvim_set_client_info()| (as recommended for all UIs |dev-ui|)
+and sets these fields on its channel: >
+
+  client = {
+    attributes = {
+      license = 'Apache 2',
+      pid = …,
+      website = 'https://neovim.io',
+    },
+    name = 'nvim-tui',
+    type = 'ui',
+    version = { … },
+  }
 
 Nvim guesses the terminal type when it starts (except in |--embed| and
 |--headless| modes). The |$TERM| environment variable is the primary hint that
 determines the terminal type.
 
 					*terminfo* *E557* *E558* *E559*
-The terminfo database is used if available.
-
-The Unibilium library (used by Nvim to read terminfo) allows you to override
-the system terminfo with one in $HOME/.terminfo/ directory, in part or in
-whole.
-
-Building your own terminfo is usually as simple as running this as
-a non-superuser:
+To display its user interface, Nvim reads a list of "terminal capabilities"
+from the system terminfo database (or builtin defaults if terminfo is not
+found). If that information is wrong, the screen may be messed up or keys may
+not be recognized.
+
+The Unibilium library (used to read terminfo) allows you to override the
+system terminfo with one in the "$HOME/.terminfo/" directory. Building your
+own terminfo is usually as simple as running this:
 >
   curl -LO https://invisible-island.net/datafiles/current/terminfo.src.gz
   gunzip terminfo.src.gz
diff --git a/runtime/doc/ui.txt b/runtime/doc/ui.txt
index 1f5132bd30..42dfcd2fe7 100644
--- a/runtime/doc/ui.txt
+++ b/runtime/doc/ui.txt
@@ -9,7 +9,7 @@ Nvim UI protocol					*UI* *ui*
                                       Type |gO| to see the table of contents.
 
 ==============================================================================
-UI Events						*ui-events*
+UI Events						*ui-protocol* *ui-events*
 
 UIs can be implemented as external client processes communicating with Nvim
 over the RPC API. The default UI model is a terminal-like grid with a single,
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index fe263d051d..d10ee91042 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -1586,6 +1586,7 @@ Array nvim_get_api_info(uint64_t channel_id, Arena *arena)
 ///
 /// @param attributes Arbitrary string:string map of informal client properties.
 ///     Suggested keys:
+///     - "pid":     Process id.
 ///     - "website": Client homepage URL (e.g. GitHub repository)
 ///     - "license": License description ("Apache 2", "GPLv3", "MIT", …)
 ///     - "logo":    URI or path to image, preferably small logo or icon.
@@ -1627,7 +1628,7 @@ void nvim_set_client_info(uint64_t channel_id, String name, Dictionary version,
 /// Gets information about a channel.
 ///
 /// @param chan channel_id, or 0 for current channel
-/// @returns Dictionary describing a channel, with these keys:
+/// @returns Channel info dict with these keys:
 ///    - "id"       Channel id.
 ///    - "argv"     (optional) Job arguments list.
 ///    - "stream"   Stream underlying the channel.
@@ -1639,14 +1640,12 @@ void nvim_set_client_info(uint64_t channel_id, String name, Dictionary version,
 ///         - "bytes"      Send and receive raw bytes.
 ///         - "terminal"   |terminal| instance interprets ASCII sequences.
 ///         - "rpc"        |RPC| communication on the channel is active.
-///    -  "pty"     (optional) Name of pseudoterminal. On a POSIX system this
-///                 is a device path like "/dev/pts/1". If the name is unknown,
-///                 the key will still be present if a pty is used (e.g. for
-///                 conpty on Windows).
-///    -  "buffer"  (optional) Buffer with connected |terminal| instance.
-///    -  "client"  (optional) Info about the peer (client on the other end of
-///                 the RPC channel), if provided by it via
-///                 |nvim_set_client_info()|.
+///    -  "pty"     (optional) Name of pseudoterminal. On a POSIX system this is a device path like
+///                 "/dev/pts/1". If unknown, the key will still be present if a pty is used (e.g.
+///                 for conpty on Windows).
+///    -  "buffer"  (optional) Buffer connected to |terminal| instance.
+///    -  "client"  (optional) Info about the peer (client on the other end of the RPC channel),
+///                 which it provided via |nvim_set_client_info()|.
 ///
 Dictionary nvim_get_chan_info(uint64_t channel_id, Integer chan, Arena *arena, Error *err)
   FUNC_API_SINCE(4)
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 0b49ea13d7..e060d0dcaf 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -351,7 +351,6 @@ int main(int argc, char **argv)
 
   // NORETURN: Start builtin UI client.
   if (ui_client_channel_id) {
-    time_finish();
     ui_client_run(remote_ui);  // NORETURN
   }
   assert(!ui_client_channel_id && !use_builtin_ui);
@@ -1514,7 +1513,7 @@ static void init_startuptime(mparm_T *paramp)
   }
   for (int i = 1; i < paramp->argc - 1; i++) {
     if (STRICMP(paramp->argv[i], "--startuptime") == 0) {
-      time_init(paramp->argv[i + 1], is_embed ? "Embedded" : "Primary/TUI");
+      time_init(paramp->argv[i + 1], is_embed ? "Embedded" : "Primary (or UI client)");
       time_start("--- NVIM STARTING ---");
       break;
     }
diff --git a/src/nvim/tui/input.c b/src/nvim/tui/input.c
index 3eb8d4ba2e..98dd7b4b45 100644
--- a/src/nvim/tui/input.c
+++ b/src/nvim/tui/input.c
@@ -464,7 +464,7 @@ static void tinput_timer_cb(uv_timer_t *handle)
 {
   TermInput *input = handle->data;
   // If the raw buffer is not empty, process the raw buffer first because it is
-  // processing an incomplete bracketed paster sequence.
+  // processing an incomplete bracketed paste sequence.
   size_t size = rstream_available(&input->read_stream);
   if (size) {
     size_t consumed = handle_raw_buffer(input, true, input->read_stream.read_pos, size);
diff --git a/src/nvim/ui.c b/src/nvim/ui.c
index 314d322a68..587124fab0 100644
--- a/src/nvim/ui.c
+++ b/src/nvim/ui.c
@@ -182,9 +182,10 @@ bool ui_override(void)
   return false;
 }
 
-bool ui_active(void)
+/// Gets the number of UIs connected to this server.
+size_t ui_active(void)
 {
-  return ui_count > 0;
+  return ui_count;
 }
 
 void ui_refresh(void)
@@ -197,7 +198,7 @@ void ui_refresh(void)
   int height = INT_MAX;
   bool ext_widgets[kUIExtCount];
   bool inclusive = ui_override();
-  memset(ext_widgets, ui_active(), ARRAY_SIZE(ext_widgets));
+  memset(ext_widgets, !!ui_active(), ARRAY_SIZE(ext_widgets));
 
   for (size_t i = 0; i < ui_count; i++) {
     RemoteUI *ui = uis[i];
diff --git a/src/nvim/ui_client.c b/src/nvim/ui_client.c
index cfa79b9d8c..43ab238716 100644
--- a/src/nvim/ui_client.c
+++ b/src/nvim/ui_client.c
@@ -24,6 +24,7 @@
 #include "nvim/msgpack_rpc/channel_defs.h"
 #include "nvim/os/os.h"
 #include "nvim/os/os_defs.h"
+#include "nvim/profile.h"
 #include "nvim/tui/tui.h"
 #include "nvim/tui/tui_defs.h"
 #include "nvim/ui.h"
@@ -81,12 +82,15 @@ uint64_t ui_client_start_server(int argc, char **argv)
   return channel->id;
 }
 
+/// Attaches this client to the UI channel, and sets its client info.
 void ui_client_attach(int width, int height, char *term, bool rgb)
 {
+  //
+  // nvim_ui_attach
+  //
   MAXSIZE_TEMP_ARRAY(args, 3);
   ADD_C(args, INTEGER_OBJ(width));
   ADD_C(args, INTEGER_OBJ(height));
-
   MAXSIZE_TEMP_DICT(opts, 9);
   PUT_C(opts, "rgb", BOOLEAN_OBJ(rgb));
   PUT_C(opts, "ext_linegrid", BOOLEAN_OBJ(true));
@@ -94,7 +98,6 @@ void ui_client_attach(int width, int height, char *term, bool rgb)
   if (term) {
     PUT_C(opts, "term_name", CSTR_AS_OBJ(term));
   }
-
   PUT_C(opts, "term_colors", INTEGER_OBJ(t_colors));
   if (!ui_client_is_remote) {
     PUT_C(opts, "stdin_tty", BOOLEAN_OBJ(stdin_isatty));
@@ -108,6 +111,40 @@ void ui_client_attach(int width, int height, char *term, bool rgb)
 
   rpc_send_event(ui_client_channel_id, "nvim_ui_attach", args);
   ui_client_attached = true;
+
+  TIME_MSG("nvim_ui_attach");
+
+  //
+  // nvim_set_client_info
+  //
+  MAXSIZE_TEMP_ARRAY(args2, 5);
+  ADD_C(args2, CSTR_AS_OBJ("nvim-tui"));            // name
+  Object m = api_metadata();
+  Dictionary version = { 0 };
+  assert(m.data.dictionary.size > 0);
+  for (size_t i = 0; i < m.data.dictionary.size; i++) {
+    if (strequal(m.data.dictionary.items[i].key.data, "version")) {
+      version = m.data.dictionary.items[i].value.data.dictionary;
+      break;
+    } else if (i + 1 == m.data.dictionary.size) {
+      abort();
+    }
+  }
+  ADD_C(args2, DICTIONARY_OBJ(version));            // version
+  ADD_C(args2, CSTR_AS_OBJ("ui"));                  // type
+  // We don't send api_metadata.functions as the "methods" because:
+  // 1. it consumes memory.
+  // 2. it is unlikely to be useful, since the peer can just call `nvim_get_api`.
+  // 3. nvim_set_client_info expects a dict instead of an array.
+  ADD_C(args2, ARRAY_OBJ((Array)ARRAY_DICT_INIT));  // methods
+  MAXSIZE_TEMP_DICT(info, 9);                       // attributes
+  PUT_C(info, "website", CSTR_AS_OBJ("https://neovim.io"));
+  PUT_C(info, "license", CSTR_AS_OBJ("Apache 2"));
+  PUT_C(info, "pid", INTEGER_OBJ(os_get_pid()));
+  ADD_C(args2, DICTIONARY_OBJ(info));               // attributes
+  rpc_send_event(ui_client_channel_id, "nvim_set_client_info", args2);
+
+  TIME_MSG("nvim_set_client_info");
 }
 
 void ui_client_detach(void)
@@ -132,6 +169,8 @@ void ui_client_run(bool remote_ui)
     ELOG("test log message");
   }
 
+  time_finish();
+
   // os_exit() will be invoked when the client channel detaches
   while (true) {
     LOOP_PROCESS_EVENTS(&main_loop, resize_events, -1);
diff --git a/test/client/session.lua b/test/client/session.lua
index 38d81eff83..bfce4eedc7 100644
--- a/test/client/session.lua
+++ b/test/client/session.lua
@@ -96,8 +96,7 @@ end
 
 --- @param method string
 --- @param ... any
---- @return boolean
---- @return table
+--- @return boolean, table
 function Session:request(method, ...)
   local args = { ... }
   local err, result
diff --git a/test/functional/terminal/tui_spec.lua b/test/functional/terminal/tui_spec.lua
index 6375e6fbae..3e837e796d 100644
--- a/test/functional/terminal/tui_spec.lua
+++ b/test/functional/terminal/tui_spec.lua
@@ -40,8 +40,8 @@ if t.skip(is_os('win')) then
 end
 
 describe('TUI', function()
-  local screen
-  local child_session
+  local screen --[[@type test.functional.ui.screen]]
+  local child_session --[[@type test.Session]]
   local child_exec_lua
 
   before_each(function()
@@ -1651,12 +1651,13 @@ describe('TUI', function()
     ]])
   end)
 
-  it('in nvim_list_uis()', function()
+  it('in nvim_list_uis(), sets nvim_set_client_info()', function()
     -- $TERM in :terminal.
     local exp_term = is_os('bsd') and 'builtin_xterm' or 'xterm-256color'
+    local ui_chan = 1
     local expected = {
       {
-        chan = 1,
+        chan = ui_chan,
         ext_cmdline = false,
         ext_hlstate = false,
         ext_linegrid = true,
@@ -1679,6 +1680,43 @@ describe('TUI', function()
     }
     local _, rv = child_session:request('nvim_list_uis')
     eq(expected, rv)
+
+    ---@type table
+    local expected_version = ({
+      child_session:request('nvim_exec_lua', 'return vim.version()', {}),
+    })[2]
+    -- vim.version() returns `prerelease` string. Coerce it to boolean.
+    expected_version.prerelease = not not expected_version.prerelease
+
+    local expected_chan_info = {
+      client = {
+        attributes = {
+          license = 'Apache 2',
+          -- pid = 5371,
+          website = 'https://neovim.io',
+        },
+        methods = {},
+        name = 'nvim-tui',
+        type = 'ui',
+        version = expected_version,
+      },
+      id = ui_chan,
+      mode = 'rpc',
+      stream = 'stdio',
+    }
+
+    local status, chan_info = child_session:request('nvim_get_chan_info', ui_chan)
+    ok(status)
+    local info = chan_info.client
+    ok(info.attributes.pid and info.attributes.pid > 0, 'PID', info.attributes.pid or 'nil')
+    ok(info.version.major >= 0)
+    ok(info.version.minor >= 0)
+    ok(info.version.patch >= 0)
+
+    -- Delete variable fields so we can deep-compare.
+    info.attributes.pid = nil
+
+    eq(expected_chan_info, chan_info)
   end)
 
   it('allows grid to assume wider ambiwidth chars than host terminal', function()
diff --git a/test/functional/testnvim.lua b/test/functional/testnvim.lua
index a66f0cd52c..ac2ec89271 100644
--- a/test/functional/testnvim.lua
+++ b/test/functional/testnvim.lua
@@ -458,7 +458,7 @@ end
 --- @param argv string[]
 --- @param merge boolean?
 --- @param env string[]?
---- @param keep boolean
+--- @param keep boolean?
 --- @param io_extra uv.uv_pipe_t? used for stdin_fd, see :help ui-option
 --- @return test.Session
 function M.spawn(argv, merge, env, keep, io_extra)