Reset stop_insert_mode in terminal_enter rather than terminal_check

Problem: Using `:stopinsert` while in normal mode in a terminal buffer
prevents neovim from entering insert mode.

Solution: Move `stop_insert_mode = false` from terminal_check to
terminal_enter to be consistent with edit.c, as suggested by bfredl in
 #9889.

Closes https://github.com/neovim/neovim/issues/9889.

2 files changed, 10 insertions, 1 deletions

diff --git a/src/nvim/terminal.c b/src/nvim/terminal.c
index 79b0df842f..a802a1ffc6 100644
--- a/src/nvim/terminal.c
+++ b/src/nvim/terminal.c
@@ -374,6 +374,7 @@ void terminal_enter(void)
   TerminalState state, *s = &state;
   memset(s, 0, sizeof(TerminalState));
   s->term = buf->terminal;
+  stop_insert_mode = false;
 
   // Ensure the terminal is properly sized. Ideally window size management
   // code should always have resized the terminal already, but check here to
@@ -435,7 +436,6 @@ void terminal_enter(void)
 static int terminal_check(VimState *state)
 {
   if (stop_insert_mode) {
-    stop_insert_mode = false;
     return 0;
   }
   return 1;
diff --git a/test/functional/terminal/ex_terminal_spec.lua b/test/functional/terminal/ex_terminal_spec.lua
index ca5737db7f..f3849709e3 100644
--- a/test/functional/terminal/ex_terminal_spec.lua
+++ b/test/functional/terminal/ex_terminal_spec.lua
@@ -106,6 +106,15 @@ describe(':terminal', function()
     command('stopinsert')
     eq({ blocking=false, mode='n' }, nvim('get_mode'))
   end)
+
+  it(':stopinsert in normal mode doesn\'t break insert mode #9889', function()
+    command(':terminal')
+    eq({ blocking=false, mode='n' }, nvim('get_mode'))
+    command(':stopinsert')
+    eq({ blocking=false, mode='n' }, nvim('get_mode'))
+    feed('a')
+    eq({ blocking=false, mode='t' }, nvim('get_mode'))
+  end)
 end)
 
 describe(':terminal (with fake shell)', function()