vim-patch:8.2.3829: no error when setting a func option to script-local function

Problem:    No error when setting a func option to a script-local function.
Solution:   Give an error if the name starts with "s:". (closes vim/vim#9358)

94c785d235

Omit test: reverted in patch 8.2.3838.
Cherry-pick SCRIPT_ID_VALID from patch 8.2.1539.

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

src/nvim/option.c

@@ -5157,6 +5157,10 @@ int option_set_callback_func(char *optval, Callback *optcb)
     return OK;
   }
 
+  if (strncmp(optval, "s:", 2) == 0 && !SCRIPT_ID_VALID(current_sctx.sc_sid)) {
+    return FAIL;
+  }
+
   typval_T *tv;
   if (*optval == '{'
       || (strncmp(optval, "function(", 9) == 0)

src/nvim/runtime.h

@@ -79,6 +79,7 @@ typedef struct scriptitem_S {
 /// Growarray to store info about already sourced scripts.
 extern garray_T script_items;
 #define SCRIPT_ITEM(id) (((scriptitem_T *)script_items.ga_data)[(id) - 1])
+#define SCRIPT_ID_VALID(id) ((id) > 0 && (id) <= script_items.ga_len)
 
 typedef void (*DoInRuntimepathCB)(char *, void *);
 

src/nvim/testdir/test_tagfunc.vim

@@ -1,6 +1,8 @@
 " Test 'tagfunc'
 
 source vim9.vim
+source check.vim
+source screendump.vim
 
 func TagFunc(pat, flag, info)
   let g:tagfunc_args = [a:pat, a:flag, a:info]