refactor: replace unnecessary helper functions in optionstr.c

Replaces unnecessary helper functions in `optionstr.c` such as
`get_option_flags()`, `get_option_fullname()`, `set_option_flag()`,
`is_global_option()`, etc. with a single `get_option()` helper function
that allows direct access to the `options` array.

Also refactors `f_exists()` to use `get_varp_scope` instead of using
`get_option_tv`. This opens up the path for removing `getoptions_T`
altogether later down the line since the hidden option logic is no
longer needed.

1 files changed, 8 insertions, 3 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 9ba2ce2365..f2ef8e5cdd 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -1938,9 +1938,14 @@ static void f_exists(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
       xfree(exp);
     }
   } else if (*p == '&' || *p == '+') {  // Option.
-    n = (get_option_tv(&p, NULL, true) == OK);
-    if (*skipwhite(p) != NUL) {
-      n = false;  // Trailing garbage.
+    bool working = (*p == '+');  // whether option needs to be working
+    int opt_flags;
+
+    if (find_option_end(&p, &opt_flags) != NULL) {
+      int opt_idx = findoption(p);
+      n = (opt_idx >= 0 && (!working || get_varp_scope(get_option(opt_idx), opt_flags) != NULL));
+    } else {
+      n = false;
     }
   } else if (*p == '*') {  // Internal or user defined function.
     n = function_exists(p + 1, false);