Merge pull request #21885 from lewis6991/refactor/options

Problems:
    - Scope of local variables in options code is too large.
    - did_set_string_option() is too large (>1000LOC).
    - Setting options for a particular window or buffer requires a changing context (assigning curwin/curbuf).

Solutions:
    - Reduce the scope of local variables.
    - Break up did_set_string_option so it doesn't contain specific logic about each individual option (1038 LOC -> 310 LOC).
    - Begin work on making functions not depend on curbuf or curwin and pass window or buffer handles explicitly.

src/nvim/edit.c

@@ -3474,7 +3474,7 @@ static void ins_ctrl_hat(void)
       State |= MODE_LANGMAP;
     }
   }
-  set_iminsert_global();
+  set_iminsert_global(curbuf);
   showmode();
   // Show/unshow value of 'keymap' in status lines.
   status_redraw_curbuf();

src/nvim/ex_getln.c

@@ -1557,9 +1557,9 @@ static void command_line_toggle_langmap(CommandLineState *s)
 
   if (s->b_im_ptr != NULL) {
     if (s->b_im_ptr == &curbuf->b_p_iminsert) {
-      set_iminsert_global();
+      set_iminsert_global(curbuf);
     } else {
-      set_imsearch_global();
+      set_imsearch_global(curbuf);
     }
   }
   ui_cursor_shape();                // may show different cursor shape

src/nvim/insexpand.c

@@ -2258,14 +2258,14 @@ static void copy_global_to_buflocal_cb(Callback *globcb, Callback *bufcb)
 /// Invoked when the 'completefunc' option is set. The option value can be a
 /// name of a function (string), or function(<name>) or funcref(<name>) or a
 /// lambda expression.
-int set_completefunc_option(void)
+void set_completefunc_option(char **errmsg)
 {
-  int retval = option_set_callback_func(curbuf->b_p_cfu, &cfu_cb);
-  if (retval == OK) {
-    set_buflocal_cfu_callback(curbuf);
+  if (option_set_callback_func(curbuf->b_p_cfu, &cfu_cb) == FAIL) {
+    *errmsg = e_invarg;
+    return;
   }
 
-  return retval;
+  set_buflocal_cfu_callback(curbuf);
 }
 
 /// Copy the global 'completefunc' callback function to the buffer-local
@@ -2279,14 +2279,13 @@ void set_buflocal_cfu_callback(buf_T *buf)
 /// Invoked when the 'omnifunc' option is set. The option value can be a
 /// name of a function (string), or function(<name>) or funcref(<name>) or a
 /// lambda expression.
-int set_omnifunc_option(void)
+void set_omnifunc_option(buf_T *buf, char **errmsg)
 {
-  int retval = option_set_callback_func(curbuf->b_p_ofu, &ofu_cb);
-  if (retval == OK) {
-    set_buflocal_ofu_callback(curbuf);
+  if (option_set_callback_func(buf->b_p_ofu, &ofu_cb) == FAIL) {
+    *errmsg = e_invarg;
+    return;
   }
-
-  return retval;
+  set_buflocal_ofu_callback(buf);
 }
 
 /// Copy the global 'omnifunc' callback function to the buffer-local 'omnifunc'
@@ -2300,7 +2299,7 @@ void set_buflocal_ofu_callback(buf_T *buf)
 /// Invoked when the 'thesaurusfunc' option is set. The option value can be a
 /// name of a function (string), or function(<name>) or funcref(<name>) or a
 /// lambda expression.
-int set_thesaurusfunc_option(void)
+void set_thesaurusfunc_option(char **errmsg)
 {
   int retval;
 
@@ -2312,7 +2311,9 @@ int set_thesaurusfunc_option(void)
     retval = option_set_callback_func(p_tsrfu, &tsrfu_cb);
   }
 
-  return retval;
+  if (retval == FAIL) {
+    *errmsg = e_invarg;
+  }
 }
 
 /// Mark the global 'completefunc' 'omnifunc' and 'thesaurusfunc' callbacks with

src/nvim/ops.c

@@ -5626,10 +5626,11 @@ static void op_colon(oparg_T *oap)
 static Callback opfunc_cb;
 
 /// Process the 'operatorfunc' option value.
-/// @return  OK or FAIL
-int set_operatorfunc_option(void)
+void set_operatorfunc_option(char **errmsg)
 {
-  return option_set_callback_func(p_opfunc, &opfunc_cb);
+  if (option_set_callback_func(p_opfunc, &opfunc_cb) == FAIL) {
+    *errmsg = e_invarg;
+  }
 }
 
 #if defined(EXITFREE)

src/nvim/quickfix.c

@@ -3854,10 +3854,11 @@ static buf_T *qf_find_buf(qf_info_T *qi)
 }
 
 /// Process the 'quickfixtextfunc' option value.
-/// @return  OK or FAIL
-int qf_process_qftf_option(void)
+void qf_process_qftf_option(char **errmsg)
 {
-  return option_set_callback_func(p_qftf, &qftf_cb);
+  if (option_set_callback_func(p_qftf, &qftf_cb) == FAIL) {
+    *errmsg = e_invarg;
+  }
 }
 
 /// Update the w:quickfix_title variable in the quickfix/location list window in

src/nvim/tag.c

@@ -210,22 +210,20 @@ static Callback tfu_cb;         // 'tagfunc' callback function
 /// Reads the 'tagfunc' option value and convert that to a callback value.
 /// Invoked when the 'tagfunc' option is set. The option value can be a name of
 /// a function (string), or function(<name>) or funcref(<name>) or a lambda.
-int set_tagfunc_option(void)
+void set_tagfunc_option(char **errmsg)
 {
   callback_free(&tfu_cb);
   callback_free(&curbuf->b_tfu_cb);
 
   if (*curbuf->b_p_tfu == NUL) {
-    return OK;
+    return;
   }
 
   if (option_set_callback_func(curbuf->b_p_tfu, &tfu_cb) == FAIL) {
-    return FAIL;
+    *errmsg = e_invarg;
   }
 
   callback_copy(&curbuf->b_tfu_cb, &tfu_cb);
-
-  return OK;
 }
 
 #if defined(EXITFREE)