startup: always wait for UI with --embed, unless --headless also is supplied

13 files changed, 70 insertions, 81 deletions

diff --git a/runtime/doc/starting.txt b/runtime/doc/starting.txt
index 275b08b5dd..dd9f9ad0f3 100644
--- a/runtime/doc/starting.txt
+++ b/runtime/doc/starting.txt
@@ -348,30 +348,35 @@ argument.
 
 							*--embed*
 --embed		Use stdin/stdout as a msgpack-RPC channel, so applications can
-		embed and control Nvim via the |rpc-api|.  Implies |--headless|.
-
-		Nvim will wait for a single request before sourcing startup
-		files and reading buffers. This is mainly so that UIs can call
-		`nvim_ui_attach` so that the UI can show startup messages
-		and possible swap file dialog for the first loaded file. In
-		addition, a `nvim_get_api_info` call before the `nvim_ui_attach`
-		call is also allowed, so that UI features can be safely
-		detected by the UI.
-
-		To avoid this behavior, this alterative could be used instead: >
+		embed and control Nvim via the |rpc-api|.
+
+		By default nvim will wait for the embedding process to call
+		`nvim_ui_attach` before sourcing startup files and reading
+		buffers.  This is so that UI can show startup messages and
+		possible swap file dialog for the first loaded file.  The
+		process can do requests before the `nvim_ui_attach`, for
+		instance a `nvim_get_api_info` call so that UI features can be
+		safely detected by the UI before attaching.
+
+		To embed nvim without using the UI protocol, `--headless` should
+		be supplied together with `--embed`. Then initialization is
+		performed without waiting for an UI. This is also equivalent
+		to the following alternative: >
 			nvim --headless --cmd "call stdioopen({'rpc': v:true})"
 <
 		See also |channel-stdio|.
 
 							*--headless*
---headless 	Do not start the default UI, so stdio can be used as an
-		arbitrary communication channel. |channel-stdio|
+--headless 	Start nvim without an UI. The TUI is not used, so stdio
+		can be used as an arbitrary communication channel.
+		|channel-stdio| When used together with `--embed`, do not wait
+		for the embedder to attach an UI.
 
 		Also useful for scripting (tests) to see messages that would
 		not be printed by |-es|.
 
 		To detect if a UI is available, check if |nvim_list_uis()| is
-		empty after |VimEnter|.
+		empty in or after |VimEnter|.
 
 		To read stdin as text, "-" must be given explicitly:
 		--headless cannot assume that stdin is just text. >
diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 509032892b..4971753854 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -58,6 +58,21 @@ void remote_ui_disconnect(uint64_t channel_id)
   xfree(ui);
 }
 
+/// Wait until ui has connected on stdio channel.
+void remote_ui_wait_for_attach(void)
+  FUNC_API_NOEXPORT
+{
+  Channel *channel = find_channel(CHAN_STDIO);
+  if (!channel) {
+    // this function should only be called in --embed mode, stdio channel
+    // can be assumed.
+    abort();
+  }
+
+  LOOP_PROCESS_EVENTS_UNTIL(&main_loop, channel->events, -1,
+                            pmap_has(uint64_t)(connected_uis, CHAN_STDIO));
+}
+
 void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height,
                     Dictionary options, Error *err)
   FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
diff --git a/src/nvim/channel.c b/src/nvim/channel.c
index 36423d0aa1..259f1cc600 100644
--- a/src/nvim/channel.c
+++ b/src/nvim/channel.c
@@ -432,7 +432,7 @@ uint64_t channel_from_stdio(bool rpc, CallbackReader on_output,
                             const char **error)
   FUNC_ATTR_NONNULL_ALL
 {
-  if (!headless_mode) {
+  if (!headless_mode && !embedded_mode) {
     *error = _("can only be opened in headless mode");
     return 0;
   }
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 192e7d2907..4b838a837c 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -65,6 +65,7 @@
 #include "nvim/msgpack_rpc/helpers.h"
 #include "nvim/msgpack_rpc/server.h"
 #include "nvim/msgpack_rpc/channel.h"
+#include "nvim/api/ui.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/private/handle.h"
@@ -304,6 +305,7 @@ int main(int argc, char **argv)
   // Read ex-commands if invoked with "-es".
   //
   bool reading_tty = !headless_mode
+                     && !embedded_mode
                      && !silent_mode
                      && (params.input_isatty || params.output_isatty
                          || params.err_isatty);
@@ -348,18 +350,16 @@ int main(int argc, char **argv)
   // startup. This allows an external UI to show messages and prompts from
   // --cmd and buffer loading (e.g. swap files)
   bool early_ui = false;
-  if (embedded_mode) {
+  if (embedded_mode && !headless_mode) {
     TIME_MSG("waiting for embedder to make request");
-    rpc_wait_for_request();
+    remote_ui_wait_for_attach();
     TIME_MSG("done waiting for embedder");
 
-    if (ui_active()) {
-      // prepare screen now, so external UIs can display messages
-      starting = NO_BUFFERS;
-      screenclear();
-      early_ui = true;
-      TIME_MSG("initialized screen early for embedder");
-    }
+    // prepare screen now, so external UIs can display messages
+    starting = NO_BUFFERS;
+    screenclear();
+    early_ui = true;
+    TIME_MSG("initialized screen early for embedder");
   }
 
   // Execute --cmd arguments.
@@ -467,7 +467,7 @@ int main(int argc, char **argv)
     wait_return(true);
   }
 
-  if (!headless_mode && !silent_mode) {
+  if (!headless_mode && !embedded_mode && !silent_mode) {
     input_stop();  // Stop reading input, let the UI take over.
     ui_builtin_start();
   }
@@ -848,7 +848,6 @@ static void command_line_scan(mparm_T *parmp)
             headless_mode = true;
           } else if (STRICMP(argv[0] + argv_idx, "embed") == 0) {
             embedded_mode = true;
-            headless_mode = true;
             const char *err;
             if (!channel_from_stdio(true, CALLBACK_READER_INIT, &err)) {
               abort();
diff --git a/src/nvim/msgpack_rpc/channel.c b/src/nvim/msgpack_rpc/channel.c
index c6cfb1a9ce..3356cdc61e 100644
--- a/src/nvim/msgpack_rpc/channel.c
+++ b/src/nvim/msgpack_rpc/channel.c
@@ -40,8 +40,6 @@
 static PMap(cstr_t) *event_strings = NULL;
 static msgpack_sbuffer out_buffer;
 
-static bool got_stdio_request = false;
-
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "msgpack_rpc/channel.c.generated.h"
 #endif
@@ -331,9 +329,6 @@ static void handle_request(Channel *channel, msgpack_object *request)
     send_error(channel, request_id, error.msg);
     api_clear_error(&error);
     api_free_array(args);
-    if (channel->id == CHAN_STDIO) {
-      got_stdio_request = true;
-    }
     return;
   }
 
@@ -349,9 +344,6 @@ static void handle_request(Channel *channel, msgpack_object *request)
     if (is_get_mode && !input_blocking()) {
       // Defer the event to a special queue used by os/input.c. #6247
       multiqueue_put(ch_before_blocking_events, on_request_event, 1, evdata);
-      if (channel->id == CHAN_STDIO) {
-        got_stdio_request = true;
-      }
     } else {
       // Invoke immediately.
       on_request_event((void **)&evdata);
@@ -387,11 +379,6 @@ static void on_request_event(void **argv)
   channel_decref(channel);
   xfree(e);
   api_clear_error(&error);
-  bool is_api_info = handler.fn == handle_nvim_get_api_info;
-  // api info is used to initiate client library, ignore it
-  if (channel->id == CHAN_STDIO && !is_api_info) {
-    got_stdio_request = true;
-  }
 }
 
 static bool channel_write(Channel *channel, WBuffer *buffer)
@@ -757,17 +744,3 @@ static void log_msg_close(FILE *f, msgpack_object msg)
   log_unlock();
 }
 #endif
-
-/// Wait until embedder has done a request
-void rpc_wait_for_request(void)
-{
-  Channel *channel = find_rpc_channel(CHAN_STDIO);
-  if (!channel) {
-    // this function should only be called in --embed mode, stdio channel
-    // can be assumed.
-    abort();
-  }
-
-  LOOP_PROCESS_EVENTS_UNTIL(&main_loop, channel->events, -1, got_stdio_request);
-}
-
diff --git a/test/functional/api/server_requests_spec.lua b/test/functional/api/server_requests_spec.lua
index 856e5ca4d2..4d25ba0819 100644
--- a/test/functional/api/server_requests_spec.lua
+++ b/test/functional/api/server_requests_spec.lua
@@ -9,7 +9,7 @@ local nvim_prog, command, funcs = helpers.nvim_prog, helpers.command, helpers.fu
 local source, next_msg = helpers.source, helpers.next_msg
 local ok = helpers.ok
 local meths = helpers.meths
-local spawn, nvim_argv = helpers.spawn, helpers.nvim_argv
+local spawn, merge_args = helpers.spawn, helpers.merge_args
 local set_session = helpers.set_session
 local expect_err = helpers.expect_err
 
@@ -23,7 +23,7 @@ describe('server -> client', function()
 
   it('handles unexpected closed stream while preparing RPC response', function()
     source([[
-      let g:_nvim_args = [v:progpath, '--embed', '-n', '-u', 'NONE', '-i', 'NONE', ]
+      let g:_nvim_args = [v:progpath, '--embed', '--headless', '-n', '-u', 'NONE', '-i', 'NONE', ]
       let ch1 = jobstart(g:_nvim_args, {'rpc': v:true})
       let child1_ch = rpcrequest(ch1, "nvim_get_api_info")[0]
       call rpcnotify(ch1, 'nvim_eval', 'rpcrequest('.child1_ch.', "nvim_get_api_info")')
@@ -189,7 +189,7 @@ describe('server -> client', function()
     end
 
     before_each(function()
-      command("let vim = rpcstart('"..nvim_prog.."', ['-u', 'NONE', '-i', 'NONE', '--cmd', 'set noswapfile', '--embed'])")
+      command("let vim = rpcstart('"..nvim_prog.."', ['-u', 'NONE', '-i', 'NONE', '--cmd', 'set noswapfile', '--embed', '--headless'])")
       neq(0, eval('vim'))
     end)
 
@@ -268,6 +268,7 @@ describe('server -> client', function()
   end)
 
   describe('connecting to another (peer) nvim', function()
+    local nvim_argv = merge_args(helpers.nvim_argv, {'--headless'})
     local function connect_test(server, mode, address)
       local serverpid = funcs.getpid()
       local client = spawn(nvim_argv)
diff --git a/test/functional/ex_cmds/oldfiles_spec.lua b/test/functional/ex_cmds/oldfiles_spec.lua
index 448326cdfb..e2958c2924 100644
--- a/test/functional/ex_cmds/oldfiles_spec.lua
+++ b/test/functional/ex_cmds/oldfiles_spec.lua
@@ -9,7 +9,7 @@ local eval = helpers.eval
 local shada_file = 'Xtest.shada'
 
 local function _clear()
-  set_session(spawn({nvim_prog, '--embed', '-u', 'NONE',
+  set_session(spawn({nvim_prog, '--embed', '--headless', '-u', 'NONE',
                      -- Need shada for these tests.
                      '-i', shada_file,
                      '--cmd', 'set noswapfile undodir=. directory=. viewdir=. backupdir=. belloff= noshowcmd noruler'}))
diff --git a/test/functional/helpers.lua b/test/functional/helpers.lua
index 8823a6e003..a51eca7fdc 100644
--- a/test/functional/helpers.lua
+++ b/test/functional/helpers.lua
@@ -330,6 +330,7 @@ local function clear(...)
   local new_args
   local env = nil
   local opts = select(1, ...)
+  local headless = true
   if type(opts) == 'table' then
     if opts.env then
       local env_tbl = {}
@@ -355,15 +356,19 @@ local function clear(...)
       end
     end
     new_args = opts.args or {}
+    if opts.headless == false then
+      headless = false
+    end
   else
     new_args = {...}
   end
+  if headless then
+    table.insert(args, '--headless')
+  end
   for _, arg in ipairs(new_args) do
     table.insert(args, arg)
   end
   set_session(spawn(args, nil, env))
-  -- Dummy request so that --embed continues past UI initialization
-  session:request('nvim_eval', "0")
 end
 
 local function insert(...)
diff --git a/test/functional/plugin/helpers.lua b/test/functional/plugin/helpers.lua
index bd482d2db7..4359380bd7 100644
--- a/test/functional/plugin/helpers.lua
+++ b/test/functional/plugin/helpers.lua
@@ -3,7 +3,6 @@ local paths = require('test.config.paths')
 local helpers = require('test.functional.helpers')(nil)
 local spawn, set_session, nvim_prog, merge_args =
   helpers.spawn, helpers.set_session, helpers.nvim_prog, helpers.merge_args
-local request = helpers.request
 
 local additional_cmd = ''
 
@@ -14,7 +13,7 @@ local function nvim_argv(shada_file)
                      '--cmd', 'set shortmess+=I background=light noswapfile belloff= noshowcmd noruler',
                      '--cmd', 'let &runtimepath=' .. rtp_value,
                      '--cmd', additional_cmd,
-                     '--embed'}
+                     '--embed', '--headless'}
   if helpers.prepend_argv then
     return merge_args(helpers.prepend_argv, nvim_args)
   else
@@ -30,7 +29,6 @@ local function reset(...)
   end
   session = spawn(nvim_argv(...))
   set_session(session)
-  request('nvim_eval', "0")
 end
 
 local function set_additional_cmd(s)
diff --git a/test/functional/shada/helpers.lua b/test/functional/shada/helpers.lua
index 1312d762d8..d5e061bb50 100644
--- a/test/functional/shada/helpers.lua
+++ b/test/functional/shada/helpers.lua
@@ -9,9 +9,12 @@ local tmpname = helpers.tmpname()
 local append_argv = nil
 
 local function nvim_argv(shada_file, embed)
+  if embed == nil then
+    embed = true
+  end
   local argv = {nvim_prog, '-u', 'NONE', '-i', shada_file or tmpname, '-N',
                 '--cmd', 'set shortmess+=I background=light noswapfile',
-                embed or '--embed'}
+                '--headless', embed  and '--embed' or nil}
   if helpers.prepend_argv or append_argv then
     return merge_args(helpers.prepend_argv, argv, append_argv)
   else
diff --git a/test/functional/shada/marks_spec.lua b/test/functional/shada/marks_spec.lua
index 4cceae1aa3..c2f6351e00 100644
--- a/test/functional/shada/marks_spec.lua
+++ b/test/functional/shada/marks_spec.lua
@@ -224,7 +224,7 @@ describe('ShaDa support code', function()
   it('does not create incorrect file for non-existent buffers when writing from -c',
   function()
     add_argv('--cmd', 'silent edit ' .. non_existent_testfilename, '-c', 'qall')
-    local argv = nvim_argv(nil, '--headless')
+    local argv = nvim_argv(nil, false) -- no --embed
     eq('', funcs.system(argv))
     eq(0, exc_exec('rshada'))
   end)
@@ -233,7 +233,7 @@ describe('ShaDa support code', function()
   function()
     add_argv('-c', 'silent edit ' .. non_existent_testfilename,
              '-c', 'autocmd VimEnter * qall')
-    local argv = nvim_argv(nil, '--headless')
+    local argv = nvim_argv(nil, false) -- no --embed
     eq('', funcs.system(argv))
     eq(0, exc_exec('rshada'))
   end)
diff --git a/test/functional/shada/shada_spec.lua b/test/functional/shada/shada_spec.lua
index 720855860a..5f7daf73e5 100644
--- a/test/functional/shada/shada_spec.lua
+++ b/test/functional/shada/shada_spec.lua
@@ -137,7 +137,7 @@ describe('ShaDa support code', function()
 
   it('does not write NONE file', function()
     local session = spawn({nvim_prog, '-u', 'NONE', '-i', 'NONE', '--embed',
-                           '--cmd', 'qall'}, true)
+                           '--headless', '--cmd', 'qall'}, true)
     session:close()
     eq(nil, lfs.attributes('NONE'))
     eq(nil, lfs.attributes('NONE.tmp.a'))
@@ -145,8 +145,8 @@ describe('ShaDa support code', function()
 
   it('does not read NONE file', function()
     write_file('NONE', '\005\001\015\131\161na\162rX\194\162rc\145\196\001-')
-    local session = spawn({nvim_prog, '-u', 'NONE', '-i', 'NONE', '--embed'},
-                          true)
+    local session = spawn({nvim_prog, '-u', 'NONE', '-i', 'NONE', '--embed',
+                           '--headless'}, true)
     set_session(session)
     eq('', funcs.getreg('a'))
     session:close()
diff --git a/test/functional/ui/embed_spec.lua b/test/functional/ui/embed_spec.lua
index afe4db66b3..6a5227803d 100644
--- a/test/functional/ui/embed_spec.lua
+++ b/test/functional/ui/embed_spec.lua
@@ -3,18 +3,12 @@ local Screen = require('test.functional.ui.screen')
 
 local feed = helpers.feed
 local eq = helpers.eq
-local spawn, set_session = helpers.spawn, helpers.set_session
-local nvim_prog, nvim_set = helpers.nvim_prog, helpers.nvim_set
-local merge_args, prepend_argv = helpers.merge_args, helpers.prepend_argv
+local clear = helpers.clear
 
 local function test_embed(ext_newgrid)
-  local session, screen
+  local screen
   local function startup(...)
-    local nvim_argv = {nvim_prog, '-u', 'NONE', '-i', 'NONE',
-                       '--cmd', nvim_set, '--embed'}
-    nvim_argv = merge_args(prepend_argv, nvim_argv, {...})
-    session = spawn(nvim_argv)
-    set_session(session)
+    clear{headless=false, args={...}}
 
     -- attach immediately after startup, for early UI
     screen = Screen.new(60, 8)
@@ -26,10 +20,6 @@ local function test_embed(ext_newgrid)
     })
   end
 
-  after_each(function()
-    session:close()
-  end)
-
   it('can display errors', function()
     startup('--cmd', 'echoerr invalid+')
     screen:expect([[