api: {get,set}_option should {get,set} global value of local options (#6405)

- nvim_get_option should return the global default of a local option.
- nvim_set_option should set the global default of a local option.

src/nvim/api/private/helpers.c

@@ -289,7 +289,7 @@ void set_option_to(void *to, int type, String name, Object value, Error *err)
     }
   }
 
-  int opt_flags = (type ? OPT_LOCAL : OPT_GLOBAL);
+  int opt_flags = (type == SREQ_GLOBAL) ? OPT_GLOBAL : OPT_LOCAL;
 
   if (flags & SOPT_BOOL) {
     if (value.type != kObjectTypeBoolean) {

src/nvim/api/vim.c

@@ -440,7 +440,7 @@ Object nvim_get_vvar(String name, Error *err)
 ///
 /// @param name     Option name
 /// @param[out] err Error details, if any
-/// @return         Option value
+/// @return         Option value (global)
 Object nvim_get_option(String name, Error *err)
     FUNC_API_SINCE(1)
 {

src/nvim/option.c

@@ -4619,14 +4619,13 @@ int get_option_value_strict(char *name,
   }
 
   char_u *varp = NULL;
-  vimoption_T *p;
   int rv = 0;
   int opt_idx = findoption(name);
   if (opt_idx < 0) {
     return 0;
   }
 
-  p = &(options[opt_idx]);
+  vimoption_T *p = &options[opt_idx];
 
   // Hidden option
   if (p->var == NULL) {
@@ -4642,26 +4641,25 @@ int get_option_value_strict(char *name,
   }
 
   if (p->indir == PV_NONE) {
-    if (opt_type == SREQ_GLOBAL)
+    if (opt_type == SREQ_GLOBAL) {
       rv |= SOPT_GLOBAL;
-    else
-      return 0; // Did not request global-only option
+    } else {
+      return 0;  // Did not request global-only option
+    }
   } else {
     if (p->indir & PV_BOTH) {
       rv |= SOPT_GLOBAL;
-    } else if (opt_type == SREQ_GLOBAL) {
-      return 0; // Requested global option
     }
 
     if (p->indir & PV_WIN) {
       if (opt_type == SREQ_BUF) {
-        return 0; // Did not request window-local option
+        return 0;  // Requested buffer-local, not window-local option
       } else {
         rv |= SOPT_WIN;
       }
     } else if (p->indir & PV_BUF) {
       if (opt_type == SREQ_WIN) {
-        return 0; // Did not request buffer-local option
+        return 0;  // Requested window-local, not buffer-local option
       } else {
         rv |= SOPT_BUF;
       }
@@ -4673,7 +4671,11 @@ int get_option_value_strict(char *name,
   }
 
   if (opt_type == SREQ_GLOBAL) {
-    varp = p->var;
+    if (p->var == VAR_WIN) {
+      return 0;
+    } else {
+      varp = p->var;
+    }
   } else {
     if (opt_type == SREQ_BUF) {
       // Special case: 'modified' is b_changed, but we also want to
@@ -4720,7 +4722,7 @@ int get_option_value_strict(char *name,
 /// @param[in]  name  Option name.
 /// @param[in]  number  New value for the number or boolean option.
 /// @param[in]  string  New value for string option.
-/// @param[in]  opt_flags  Flags: OPT_LOCAL or 0 (both).
+/// @param[in]  opt_flags  Flags: OPT_LOCAL, OPT_GLOBAL, or 0 (both).
 ///
 /// @return NULL on success, error message on error.
 char *set_option_value(const char *const name, const long number,

src/nvim/option_defs.h

@@ -16,9 +16,9 @@
 #define SOPT_UNSET 0x40    // Option does not have local value set
 
 // Option types for various functions in option.c
-#define SREQ_GLOBAL 0 // Request global option
-#define SREQ_WIN 1    // Request window-local option
-#define SREQ_BUF 2    // Request buffer-local option
+#define SREQ_GLOBAL 0  // Request global option value
+#define SREQ_WIN 1     // Request window-local option value
+#define SREQ_BUF 2     // Request buffer-local option value
 
 /*
  * Default values for 'errorformat'.

test/functional/api/vim_spec.lua

@@ -153,6 +153,28 @@ describe('api', function()
       nvim('set_option', 'equalalways', false)
       ok(not nvim('get_option', 'equalalways'))
     end)
+
+    it('works to get global value of local options', function()
+      eq(false, nvim('get_option', 'lisp'))
+      eq(8, nvim('get_option', 'shiftwidth'))
+    end)
+
+    it('works to set global value of local options', function()
+      nvim('set_option', 'lisp', true)
+      eq(true, nvim('get_option', 'lisp'))
+      eq(false, helpers.curbuf('get_option', 'lisp'))
+      eq(nil, nvim('command_output', 'setglobal lisp?'):match('nolisp'))
+      eq('nolisp', nvim('command_output', 'setlocal lisp?'):match('nolisp'))
+      nvim('set_option', 'shiftwidth', 20)
+      eq('20', nvim('command_output', 'setglobal shiftwidth?'):match('%d+'))
+      eq('8', nvim('command_output', 'setlocal shiftwidth?'):match('%d+'))
+    end)
+
+    it('most window-local options have no global value', function()
+      local status, err = pcall(nvim, 'get_option', 'foldcolumn')
+      eq(false, status)
+      ok(err:match('Invalid option name') ~= nil)
+    end)
   end)
 
   describe('nvim_{get,set}_current_buf, nvim_list_bufs', function()