Merge #9829 'startup: remove TUI init special-case'

fixes #7967
fixes #9959

Historically Vim/Nvim does backflips to handle input and show messages
before a UI is available. This logical contradiction was already fixed
for remote UIs (#9024 c236e80cf3df). Fixing it also for the TUI avoids
problems on Windows, simplifies the logic, and avoids races like #9959.

- Move ui_builtin_start() to the same position as embedded_mode
  remote_ui_wait_for_attach().
- If stdin is redirected, save the original `stdin` and replace fd
  0 with tty before calling `ui_builtin_start()`.

1 files changed, 4 insertions, 2 deletions

diff --git a/test/functional/core/startup_spec.lua b/test/functional/core/startup_spec.lua
index f77af836a6..45bfa93b56 100644
--- a/test/functional/core/startup_spec.lua
+++ b/test/functional/core/startup_spec.lua
@@ -46,7 +46,7 @@ describe('startup', function()
     ]])
   end)
   it('in a TTY: has("ttyin")==1 has("ttyout")==1', function()
-    local screen = Screen.new(25, 3)
+    local screen = Screen.new(25, 4)
     screen:attach()
     if iswin() then
       command([[set shellcmdflag=/s\ /c shellxquote=\"]])
@@ -58,6 +58,7 @@ describe('startup', function()
             ..[[, shellescape(v:progpath))]])
     screen:expect([[
       ^                         |
+      ~                        |
       1 1                      |
                                |
     ]])
@@ -96,7 +97,7 @@ describe('startup', function()
     end)
   end)
   it('input from pipe (implicit) #7679', function()
-    local screen = Screen.new(25, 3)
+    local screen = Screen.new(25, 4)
     screen:attach()
     if iswin() then
       command([[set shellcmdflag=/s\ /c shellxquote=\"]])
@@ -109,6 +110,7 @@ describe('startup', function()
             ..[[, shellescape(v:progpath))]])
     screen:expect([[
       ^foo                      |
+      ~                        |
       0 1                      |
                                |
     ]])