vim-patch:8.1.2047: cannot check the current state

Problem:    Cannot check the current state.
Solution:   Add the state() function.

https://github.com/vim/vim/commit/0e57dd859ecb1e8a3b91509d2f4343e839340eb8

Co-authored-by: Bram Moolenaar <Bram@vim.org>

7 files changed, 161 insertions, 8 deletions

diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 92cedbdc80..c57b8637e0 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -4753,6 +4753,7 @@ mode([expr])                                                            *mode()*
 		If [expr] is supplied and it evaluates to a non-zero Number or
 		a non-empty String (|non-zero-arg|), then the full mode is
 		returned, otherwise only the first letter is returned.
+		Also see |state()|.
 
 		   n	    Normal
 		   no	    Operator-pending
@@ -7368,6 +7369,31 @@ srand([{expr}])                                                        *srand()*
 			echo rand(seed)
 <
 
+state([{what}])                                                        *state()*
+		Return a string which contains characters indicating the
+		current state.  Mostly useful in callbacks that want to do
+		work that may not always be safe.  Roughly this works like:
+		- callback uses state() to check if work is safe to do.
+		  If yes, then do it right away.
+		  Otherwise add to work queue and add SafeState autocommand.
+		- When SafeState is triggered, check with state() if the work
+		  can be done now, and if yes remove it from the queue and
+		  execute.
+		Also see |mode()|.
+
+		When {what} is given only characters in this string will be
+		added.  E.g, this checks if the screen has scrolled: >vim
+			if state('s') != ''
+
+		These characters indicate the state:
+		    m  halfway a mapping, :normal command, feedkeys() or
+		       stuffed command
+		    o  operator pending or waiting for a command argument
+		    a  Insert mode autocomplete active
+		    x  executing an autocommand
+		    c  callback invoked (repeats for recursiveness up to "ccc")
+		    s  screen has scrolled for messages
+
 stdioopen({opts})                                                  *stdioopen()*
 		With |--headless| this opens stdin and stdout as a |channel|.
 		May be called only once. See |channel-stdio|. stderr is not
diff --git a/runtime/lua/vim/_meta/vimfn.lua b/runtime/lua/vim/_meta/vimfn.lua
index 300210b296..4665f71052 100644
--- a/runtime/lua/vim/_meta/vimfn.lua
+++ b/runtime/lua/vim/_meta/vimfn.lua
@@ -5713,6 +5713,7 @@ function vim.fn.mkdir(name, flags, prot) end
 --- If [expr] is supplied and it evaluates to a non-zero Number or
 --- a non-empty String (|non-zero-arg|), then the full mode is
 --- returned, otherwise only the first letter is returned.
+--- Also see |state()|.
 ---
 ---    n      Normal
 ---    no      Operator-pending
@@ -8744,6 +8745,34 @@ function vim.fn.sqrt(expr) end
 --- @return any
 function vim.fn.srand(expr) end
 
+--- Return a string which contains characters indicating the
+--- current state.  Mostly useful in callbacks that want to do
+--- work that may not always be safe.  Roughly this works like:
+--- - callback uses state() to check if work is safe to do.
+---   If yes, then do it right away.
+---   Otherwise add to work queue and add SafeState autocommand.
+--- - When SafeState is triggered, check with state() if the work
+---   can be done now, and if yes remove it from the queue and
+---   execute.
+--- Also see |mode()|.
+---
+--- When {what} is given only characters in this string will be
+--- added.  E.g, this checks if the screen has scrolled: >vim
+---   if state('s') != ''
+---
+--- These characters indicate the state:
+---     m  halfway a mapping, :normal command, feedkeys() or
+---        stuffed command
+---     o  operator pending or waiting for a command argument
+---     a  Insert mode autocomplete active
+---     x  executing an autocommand
+---     c  callback invoked (repeats for recursiveness up to "ccc")
+---     s  screen has scrolled for messages
+---
+--- @param what? string
+--- @return any
+function vim.fn.state(what) end
+
 --- With |--headless| this opens stdin and stdout as a |channel|.
 --- May be called only once. See |channel-stdio|. stderr is not
 --- handled by this function, see |v:stderr|.
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 08c5ef743b..052d67b05f 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -5994,6 +5994,13 @@ bool callback_from_typval(Callback *const callback, const typval_T *const arg)
   return true;
 }
 
+static int callback_depth = 0;
+
+int get_callback_depth(void)
+{
+  return callback_depth;
+}
+
 /// @return  whether the callback could be called.
 bool callback_call(Callback *const callback, const int argcount_in, typval_T *const argvars_in,
                    typval_T *const rettv)
@@ -6041,7 +6048,11 @@ bool callback_call(Callback *const callback, const int argcount_in, typval_T *co
   funcexe.fe_lastline = curwin->w_cursor.lnum;
   funcexe.fe_evaluate = true;
   funcexe.fe_partial = partial;
-  return call_func(name, -1, rettv, argcount_in, argvars_in, &funcexe);
+
+  callback_depth++;
+  int ret = call_func(name, -1, rettv, argcount_in, argvars_in, &funcexe);
+  callback_depth--;
+  return ret;
 }
 
 bool set_ref_in_callback(Callback *callback, int copyID, ht_stack_T **ht_stack,
diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index be87201bbf..f244d26375 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -6917,6 +6917,7 @@ M.funcs = {
       If [expr] is supplied and it evaluates to a non-zero Number or
       a non-empty String (|non-zero-arg|), then the full mode is
       returned, otherwise only the first letter is returned.
+      Also see |state()|.
 
          n	    Normal
          no	    Operator-pending
@@ -10451,6 +10452,38 @@ M.funcs = {
     params = { { 'what', 'any' } },
     signature = 'stdpath({what})',
   },
+  state = {
+    args = {0, 1},
+    base = 1,
+    desc = [=[
+      Return a string which contains characters indicating the
+      current state.  Mostly useful in callbacks that want to do
+      work that may not always be safe.  Roughly this works like:
+      - callback uses state() to check if work is safe to do.
+        If yes, then do it right away.
+        Otherwise add to work queue and add SafeState autocommand.
+      - When SafeState is triggered, check with state() if the work
+        can be done now, and if yes remove it from the queue and
+        execute.
+      Also see |mode()|.
+
+      When {what} is given only characters in this string will be
+      added.  E.g, this checks if the screen has scrolled: >vim
+      	if state('s') != ''
+
+      These characters indicate the state:
+          m  halfway a mapping, :normal command, feedkeys() or
+             stuffed command
+          o  operator pending or waiting for a command argument
+          a  Insert mode autocomplete active
+          x  executing an autocommand
+          c  callback invoked (repeats for recursiveness up to "ccc")
+          s  screen has scrolled for messages
+    ]=],
+    name = 'state',
+    params = { { 'what', 'string' } },
+    signature = 'state([{what}])',
+  },
   str2float = {
     args = 1,
     base = 1,
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 250b5c5556..c47fd4cfcb 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -4925,6 +4925,47 @@ static void f_mode(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   rettv->v_type = VAR_STRING;
 }
 
+static void may_add_state_char(garray_T *gap, const char *include, uint8_t c)
+{
+  if (include == NULL || vim_strchr(include, c) != NULL) {
+    ga_append(gap, c);
+  }
+}
+
+/// "state()" function
+static void f_state(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  garray_T ga;
+  ga_init(&ga, 1, 20);
+  const char *include = NULL;
+
+  if (argvars[0].v_type != VAR_UNKNOWN) {
+    include = tv_get_string(&argvars[0]);
+  }
+
+  if (!(stuff_empty() && typebuf.tb_len == 0 && !using_script())) {
+    may_add_state_char(&ga, include, 'm');
+  }
+  if (op_pending()) {
+    may_add_state_char(&ga, include, 'o');
+  }
+  if (autocmd_busy) {
+    may_add_state_char(&ga, include, 'x');
+  }
+  if (!ctrl_x_mode_none()) {
+    may_add_state_char(&ga, include, 'a');
+  }
+  for (int i = 0; i < get_callback_depth() && i < 3; i++) {
+    may_add_state_char(&ga, include, 'c');
+  }
+  if (msg_scrolled > 0) {
+    may_add_state_char(&ga, include, 's');
+  }
+
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = ga.ga_data;
+}
+
 /// "msgpackdump()" function
 static void f_msgpackdump(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   FUNC_ATTR_NONNULL_ALL
diff --git a/src/nvim/generators/gen_eval.lua b/src/nvim/generators/gen_eval.lua
index c7978f0d19..0433894465 100644
--- a/src/nvim/generators/gen_eval.lua
+++ b/src/nvim/generators/gen_eval.lua
@@ -36,6 +36,7 @@ hashpipe:write([[
 #include "nvim/quickfix.h"
 #include "nvim/runtime.h"
 #include "nvim/search.h"
+#include "nvim/state.h"
 #include "nvim/strings.h"
 #include "nvim/sign.h"
 #include "nvim/testing.h"
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 324bfc0c46..56bc75d658 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -482,6 +482,20 @@ bool check_text_or_curbuf_locked(oparg_T *oap)
   return true;
 }
 
+static oparg_T *current_oap = NULL;
+
+/// Check if an operator was started but not finished yet.
+/// Includes typing a count or a register name.
+bool op_pending(void)
+{
+  return !(current_oap != NULL
+           && !finish_op
+           && current_oap->prev_opcount == 0
+           && current_oap->prev_count0 == 0
+           && current_oap->op_type == OP_NOP
+           && current_oap->regname == NUL);
+}
+
 /// Normal state entry point. This is called on:
 ///
 /// - Startup, In this case the function never returns.
@@ -490,15 +504,18 @@ bool check_text_or_curbuf_locked(oparg_T *oap)
 ///   for example. Returns when re-entering ex mode(because ex mode recursion is
 ///   not allowed)
 ///
-/// This used to be called main_loop on main.c
+/// This used to be called main_loop() on main.c
 void normal_enter(bool cmdwin, bool noexmode)
 {
   NormalState state;
   normal_state_init(&state);
+  oparg_T *prev_oap = current_oap;
+  current_oap = &state.oa;
   state.cmdwin = cmdwin;
   state.noexmode = noexmode;
   state.toplevel = (!cmdwin || cmdwin_result == 0) && !noexmode;
   state_enter(&state.state);
+  current_oap = prev_oap;
 }
 
 static void normal_prepare(NormalState *s)
@@ -1299,12 +1316,7 @@ static void normal_check_buffer_modified(NormalState *s)
 /// type a character, trigger SafeState.
 static void normal_check_safe_state(NormalState *s)
 {
-  may_trigger_safestate(!finish_op
-                        && s->oa.prev_opcount > 0
-                        && s->oa.prev_count0 == 0
-                        && s->oa.op_type == OP_NOP
-                        && s->oa.regname == NUL
-                        && restart_edit == 0);
+  may_trigger_safestate(!op_pending() && restart_edit == 0);
 }
 
 static void normal_check_folds(NormalState *s)