api: Rename dict_set_value to dict_set_var

Reasonings:
1. It is not used for anything, but scope dictionaries currenly. So there is no 
   need to generalize and split it into dict_set_var (which will contain some 
   scope-dictionary-specific checks) and dict_set_value (which will work for any 
   dictionary).
2. Check for key size is no longer valid for non-scope dictionaries: you *can* 
   use empty keys there. In scope dictionaries also, but you actually are not 
   supposed to store there anything, but variables.

Note that actually one may still do

    let b:[''] = 1

and “bypass” check for variable name. It won’t change what `echo b:` will show, 
but it may affect code which iterates over scope dictionary keys and sets them 
to something (if there is such code).

src/nvim/api/buffer.c

@@ -456,7 +456,7 @@ void nvim_buf_set_var(Buffer buffer, String name, Object value, Error *err)
     return;
   }
 
-  dict_set_value(buf->b_vars, name, value, false, false, err);
+  dict_set_var(buf->b_vars, name, value, false, false, err);
 }
 
 /// Removes a buffer-scoped (b:) variable
@@ -472,7 +472,7 @@ void nvim_buf_del_var(Buffer buffer, String name, Error *err)
     return;
   }
 
-  dict_set_value(buf->b_vars, name, NIL, true, false, err);
+  dict_set_var(buf->b_vars, name, NIL, true, false, err);
 }
 
 /// Sets a buffer-scoped (b:) variable
@@ -495,7 +495,7 @@ Object buffer_set_var(Buffer buffer, String name, Object value, Error *err)
     return (Object) OBJECT_INIT;
   }
 
-  return dict_set_value(buf->b_vars, name, value, false, true, err);
+  return dict_set_var(buf->b_vars, name, value, false, true, err);
 }
 
 /// Removes a buffer-scoped (b:) variable
@@ -514,7 +514,7 @@ Object buffer_del_var(Buffer buffer, String name, Error *err)
     return (Object) OBJECT_INIT;
   }
 
-  return dict_set_value(buf->b_vars, name, NIL, true, true, err);
+  return dict_set_var(buf->b_vars, name, NIL, true, true, err);
 }
 
 

src/nvim/api/private/helpers.c

@@ -98,7 +98,7 @@ Object dict_get_value(dict_T *dict, String key, Error *err)
   return vim_to_object(&di->di_tv);
 }
 
-/// Set a value in a dict. Objects are recursively expanded into their
+/// Set a value in a scope dict. Objects are recursively expanded into their
 /// vimscript equivalents.
 ///
 /// @param dict The vimscript dict
@@ -109,8 +109,8 @@ Object dict_get_value(dict_T *dict, String key, Error *err)
 /// @param retval If true the old value will be converted and returned.
 /// @param[out] err Details of an error that may have occurred
 /// @return The old value if `retval` is true and the key was present, else NIL
-Object dict_set_value(dict_T *dict, String key, Object value, bool del,
-                      bool retval, Error *err)
+Object dict_set_var(dict_T *dict, String key, Object value, bool del,
+                    bool retval, Error *err)
 {
   Object rv = OBJECT_INIT;
 
@@ -120,7 +120,7 @@ Object dict_set_value(dict_T *dict, String key, Object value, bool del,
   }
 
   if (key.size == 0) {
-    api_set_error(err, Validation, _("Empty dictionary keys aren't allowed"));
+    api_set_error(err, Validation, _("Empty variable names aren't allowed"));
     return rv;
   }
 
@@ -129,7 +129,7 @@ Object dict_set_value(dict_T *dict, String key, Object value, bool del,
     return rv;
   }
 
-  dictitem_T *di = dict_find(dict, (uint8_t *)key.data, (int)key.size);
+  dictitem_T *di = dict_find(dict, (char_u *)key.data, (int)key.size);
 
   if (del) {
     // Delete the key

src/nvim/api/tabpage.c

@@ -71,7 +71,7 @@ void nvim_tabpage_set_var(Tabpage tabpage,
     return;
   }
 
-  dict_set_value(tab->tp_vars, name, value, false, false, err);
+  dict_set_var(tab->tp_vars, name, value, false, false, err);
 }
 
 /// Removes a tab-scoped (t:) variable
@@ -87,7 +87,7 @@ void nvim_tabpage_del_var(Tabpage tabpage, String name, Error *err)
     return;
   }
 
-  dict_set_value(tab->tp_vars, name, NIL, true, false, err);
+  dict_set_var(tab->tp_vars, name, NIL, true, false, err);
 }
 
 /// Sets a tab-scoped (t:) variable
@@ -110,7 +110,7 @@ Object tabpage_set_var(Tabpage tabpage, String name, Object value, Error *err)
     return (Object) OBJECT_INIT;
   }
 
-  return dict_set_value(tab->tp_vars, name, value, false, true, err);
+  return dict_set_var(tab->tp_vars, name, value, false, true, err);
 }
 
 /// Removes a tab-scoped (t:) variable
@@ -129,7 +129,7 @@ Object tabpage_del_var(Tabpage tabpage, String name, Error *err)
     return (Object) OBJECT_INIT;
   }
 
-  return dict_set_value(tab->tp_vars, name, NIL, true, true, err);
+  return dict_set_var(tab->tp_vars, name, NIL, true, true, err);
 }
 
 /// Gets the current window in a tabpage

src/nvim/api/vim.c

@@ -368,7 +368,7 @@ Object nvim_get_var(String name, Error *err)
 /// @param[out] err Error details, if any
 void nvim_set_var(String name, Object value, Error *err)
 {
-  dict_set_value(&globvardict, name, value, false, false, err);
+  dict_set_var(&globvardict, name, value, false, false, err);
 }
 
 /// Removes a global (g:) variable
@@ -377,7 +377,7 @@ void nvim_set_var(String name, Object value, Error *err)
 /// @param[out] err Error details, if any
 void nvim_del_var(String name, Error *err)
 {
-  dict_set_value(&globvardict, name, NIL, true, false, err);
+  dict_set_var(&globvardict, name, NIL, true, false, err);
 }
 
 /// Sets a global variable
@@ -393,7 +393,7 @@ void nvim_del_var(String name, Error *err)
 ///                  or if previous value was `v:null`.
 Object vim_set_var(String name, Object value, Error *err)
 {
-  return dict_set_value(&globvardict, name, value, false, true, err);
+  return dict_set_var(&globvardict, name, value, false, true, err);
 }
 
 /// Removes a global variable
@@ -405,7 +405,7 @@ Object vim_set_var(String name, Object value, Error *err)
 /// @return Old value
 Object vim_del_var(String name, Error *err)
 {
-  return dict_set_value(&globvardict, name, NIL, true, true, err);
+  return dict_set_var(&globvardict, name, NIL, true, true, err);
 }
 
 /// Gets a v: variable

src/nvim/api/window.c

@@ -210,7 +210,7 @@ void nvim_win_set_var(Window window, String name, Object value, Error *err)
     return;
   }
 
-  dict_set_value(win->w_vars, name, value, false, false, err);
+  dict_set_var(win->w_vars, name, value, false, false, err);
 }
 
 /// Removes a window-scoped (w:) variable
@@ -226,7 +226,7 @@ void nvim_win_del_var(Window window, String name, Error *err)
     return;
   }
 
-  dict_set_value(win->w_vars, name, NIL, true, false, err);
+  dict_set_var(win->w_vars, name, NIL, true, false, err);
 }
 
 /// Sets a window-scoped (w:) variable
@@ -249,7 +249,7 @@ Object window_set_var(Window window, String name, Object value, Error *err)
     return (Object) OBJECT_INIT;
   }
 
-  return dict_set_value(win->w_vars, name, value, false, true, err);
+  return dict_set_var(win->w_vars, name, value, false, true, err);
 }
 
 /// Removes a window-scoped (w:) variable
@@ -268,7 +268,7 @@ Object window_del_var(Window window, String name, Error *err)
     return (Object) OBJECT_INIT;
   }
 
-  return dict_set_value(win->w_vars, name, NIL, true, true, err);
+  return dict_set_var(win->w_vars, name, NIL, true, true, err);
 }
 
 /// Gets a window option value