api: Replace set_var(name, NIL) with del_var(name)

src/nvim/api/buffer.c

@@ -423,7 +423,7 @@ Object buffer_get_var(Buffer buffer, String name, Error *err)
   return dict_get_value(buf->b_vars, name, err);
 }
 
-/// Sets a buffer-scoped (b:) variable. 'nil' value deletes the variable.
+/// Sets a buffer-scoped (b:) variable
 ///
 /// @param buffer The buffer handle
 /// @param name The variable name
@@ -438,7 +438,24 @@ 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, err);
+  return dict_set_value(buf->b_vars, name, value, false, err);
+}
+
+/// Removes a buffer-scoped (b:) variable
+///
+/// @param buffer The buffer handle
+/// @param name The variable name
+/// @param[out] err Details of an error that may have occurred
+/// @return The old value
+Object buffer_del_var(Buffer buffer, String name, Error *err)
+{
+  buf_T *buf = find_buffer_by_handle(buffer, err);
+
+  if (!buf) {
+    return (Object) OBJECT_INIT;
+  }
+
+  return dict_set_value(buf->b_vars, name, NIL, true, err);
 }
 
 /// Gets a buffer option value

src/nvim/api/private/helpers.c

@@ -90,14 +90,17 @@ Object dict_get_value(dict_T *dict, String key, Error *err)
 }
 
 /// Set a value in a dict. Objects are recursively expanded into their
-/// vimscript equivalents. Passing 'nil' as value deletes the key.
+/// vimscript equivalents.
 ///
 /// @param dict The vimscript dict
 /// @param key The key
 /// @param value The new value
+/// @param del Delete key in place of setting it. Argument `value` is ignored in
+///            this case.
 /// @param[out] err Details of an error that may have occurred
 /// @return the old value, if any
-Object dict_set_value(dict_T *dict, String key, Object value, Error *err)
+Object dict_set_value(dict_T *dict, String key, Object value, bool del,
+                      Error *err)
 {
   Object rv = OBJECT_INIT;
 
@@ -118,7 +121,7 @@ Object dict_set_value(dict_T *dict, String key, Object value, Error *err)
 
   dictitem_T *di = dict_find(dict, (uint8_t *)key.data, (int)key.size);
 
-  if (value.type == kObjectTypeNil) {
+  if (del) {
     // Delete the key
     if (di == NULL) {
       // Doesn't exist, fail

src/nvim/api/tabpage.c

@@ -54,7 +54,7 @@ Object tabpage_get_var(Tabpage tabpage, String name, Error *err)
   return dict_get_value(tab->tp_vars, name, err);
 }
 
-/// Sets a tab-scoped (t:) variable. 'nil' value deletes the variable.
+/// Sets a tab-scoped (t:) variable
 ///
 /// @param tabpage handle
 /// @param name The variable name
@@ -69,7 +69,24 @@ 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, err);
+  return dict_set_value(tab->tp_vars, name, value, false, err);
+}
+
+/// Removes a tab-scoped (t:) variable
+///
+/// @param tabpage handle
+/// @param name The variable name
+/// @param[out] err Details of an error that may have occurred
+/// @return The tab page handle
+Object tabpage_del_var(Tabpage tabpage, String name, Error *err)
+{
+  tabpage_T *tab = find_tab_by_handle(tabpage, err);
+
+  if (!tab) {
+    return (Object) OBJECT_INIT;
+  }
+
+  return dict_set_value(tab->tp_vars, name, NIL, true, err);
 }
 
 /// Gets the current window in a tab page

src/nvim/api/vim.c

@@ -331,7 +331,7 @@ Object vim_get_var(String name, Error *err)
   return dict_get_value(&globvardict, name, err);
 }
 
-/// Sets a global variable. Passing 'nil' as value deletes the variable.
+/// Sets a global variable
 ///
 /// @param name The variable name
 /// @param value The variable value
@@ -339,7 +339,17 @@ Object vim_get_var(String name, Error *err)
 /// @return the old value if any
 Object vim_set_var(String name, Object value, Error *err)
 {
-  return dict_set_value(&globvardict, name, value, err);
+  return dict_set_value(&globvardict, name, value, false, err);
+}
+
+/// Removes a global variable
+///
+/// @param name The variable name
+/// @param[out] err Details of an error that may have occurred
+/// @return the old value if any
+Object vim_del_var(String name, Error *err)
+{
+  return dict_set_value(&globvardict, name, NIL, true, err);
 }
 
 /// Gets a vim variable

src/nvim/api/window.c

@@ -197,7 +197,7 @@ Object window_get_var(Window window, String name, Error *err)
   return dict_get_value(win->w_vars, name, err);
 }
 
-/// Sets a window-scoped (w:) variable. 'nil' value deletes the variable.
+/// Sets a window-scoped (w:) variable
 ///
 /// @param window The window handle
 /// @param name The variable name
@@ -212,7 +212,24 @@ 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, err);
+  return dict_set_value(win->w_vars, name, value, false, err);
+}
+
+/// Removes a window-scoped (w:) variable
+///
+/// @param window The window handle
+/// @param name The variable name
+/// @param[out] err Details of an error that may have occurred
+/// @return The old value
+Object window_del_var(Window window, String name, Error *err)
+{
+  win_T *win = find_window_by_handle(window, err);
+
+  if (!win) {
+    return (Object) OBJECT_INIT;
+  }
+
+  return dict_set_value(win->w_vars, name, NIL, true, err);
 }
 
 /// Gets a window option value

src/nvim/eval.c

@@ -16028,9 +16028,9 @@ static void f_termopen(typval_T *argvars, typval_T *rettv)
   // Save the job id and pid in b:terminal_job_{id,pid}
   Error err;
   dict_set_value(curbuf->b_vars, cstr_as_string("terminal_job_id"),
-      INTEGER_OBJ(rettv->vval.v_number), &err);
+                 INTEGER_OBJ(rettv->vval.v_number), false, &err);
   dict_set_value(curbuf->b_vars, cstr_as_string("terminal_job_pid"),
-      INTEGER_OBJ(pid), &err);
+                 INTEGER_OBJ(pid), false, &err);
 
   Terminal *term = terminal_open(topts);
   data->term = term;

src/nvim/terminal.c

@@ -627,6 +627,7 @@ static int term_settermprop(VTermProp prop, VTermValue *val, void *data)
       api_free_object(dict_set_value(buf->b_vars,
                                      cstr_as_string("term_title"),
                                      STRING_OBJ(cstr_as_string(val->string)),
+                                     false,
                                      &err));
       break;
     }

test/functional/api/buffer_spec.lua

@@ -3,6 +3,7 @@ local helpers = require('test.functional.helpers')
 local clear, nvim, buffer = helpers.clear, helpers.nvim, helpers.buffer
 local curbuf, curwin, eq = helpers.curbuf, helpers.curwin, helpers.eq
 local curbufmeths, ok = helpers.curbufmeths, helpers.ok
+local funcs = helpers.funcs
 
 describe('buffer_* functions', function()
   before_each(clear)
@@ -234,11 +235,14 @@ describe('buffer_* functions', function()
 
   end)
 
-  describe('{get,set}_var', function()
+  describe('{get,set,del}_var', function()
     it('works', function()
       curbuf('set_var', 'lua', {1, 2, {['3'] = 1}})
       eq({1, 2, {['3'] = 1}}, curbuf('get_var', 'lua'))
       eq({1, 2, {['3'] = 1}}, nvim('eval', 'b:lua'))
+      eq(1, funcs.exists('b:lua'))
+      curbufmeths.del_var('lua')
+      eq(0, funcs.exists('b:lua'))
     end)
   end)
 

test/functional/api/tabpage_spec.lua

@@ -3,6 +3,9 @@ local helpers = require('test.functional.helpers')
 local clear, nvim, tabpage, curtab, eq, ok =
   helpers.clear, helpers.nvim, helpers.tabpage, helpers.curtab, helpers.eq,
   helpers.ok
+local wait = helpers.wait
+local curtabmeths = helpers.curtabmeths
+local funcs = helpers.funcs
 
 describe('tabpage_* functions', function()
   before_each(clear)
@@ -21,11 +24,14 @@ describe('tabpage_* functions', function()
     end)
   end)
 
-  describe('{get,set}_var', function()
+  describe('{get,set,del}_var', function()
     it('works', function()
       curtab('set_var', 'lua', {1, 2, {['3'] = 1}})
       eq({1, 2, {['3'] = 1}}, curtab('get_var', 'lua'))
       eq({1, 2, {['3'] = 1}}, nvim('eval', 't:lua'))
+      eq(1, funcs.exists('t:lua'))
+      curtabmeths.del_var('lua')
+      eq(0, funcs.exists('t:lua'))
     end)
   end)
 

test/functional/api/vim_spec.lua

@@ -4,6 +4,8 @@ local Screen = require('test.functional.ui.screen')
 local clear, nvim, eq, neq = helpers.clear, helpers.nvim, helpers.eq, helpers.neq
 local ok, nvim_async, feed = helpers.ok, helpers.nvim_async, helpers.feed
 local os_name = helpers.os_name
+local meths = helpers.meths
+local funcs = helpers.funcs
 
 describe('vim_* functions', function()
   before_each(clear)
@@ -70,11 +72,14 @@ describe('vim_* functions', function()
     end)
   end)
 
-  describe('{get,set}_var', function()
+  describe('{get,set,del}_var', function()
     it('works', function()
       nvim('set_var', 'lua', {1, 2, {['3'] = 1}})
       eq({1, 2, {['3'] = 1}}, nvim('get_var', 'lua'))
       eq({1, 2, {['3'] = 1}}, nvim('eval', 'g:lua'))
+      eq(1, funcs.exists('g:lua'))
+      meths.del_var('lua')
+      eq(0, funcs.exists('g:lua'))
     end)
 
     it('set_var returns the old value', function()
@@ -84,6 +89,14 @@ describe('vim_* functions', function()
       eq(val1, nvim('set_var', 'lua', val2))
     end)
 
+    it('del_var returns the old value', function()
+      local val1 = {1, 2, {['3'] = 1}}
+      local val2 = {4, 7}
+      eq(nil, meths.set_var('lua', val1))
+      eq(val1, meths.set_var('lua', val2))
+      eq(val2, meths.del_var('lua'))
+    end)
+
     it('truncates values with NULs in them', function()
       nvim('set_var', 'xxx', 'ab\0cd')
       eq('ab', nvim('get_var', 'xxx'))

test/functional/api/window_spec.lua

@@ -5,6 +5,8 @@ local clear, nvim, curbuf, curbuf_contents, window, curwin, eq, neq,
   helpers.curbuf_contents, helpers.window, helpers.curwin, helpers.eq,
   helpers.neq, helpers.ok, helpers.feed, helpers.insert, helpers.eval
 local wait = helpers.wait
+local curwinmeths = helpers.curwinmeths
+local funcs = helpers.funcs
 
 -- check if str is visible at the beginning of some line
 local function is_visible(str)
@@ -126,11 +128,14 @@ describe('window_* functions', function()
     end)
   end)
 
-  describe('{get,set}_var', function()
+  describe('{get,set,del}_var', function()
     it('works', function()
       curwin('set_var', 'lua', {1, 2, {['3'] = 1}})
       eq({1, 2, {['3'] = 1}}, curwin('get_var', 'lua'))
       eq({1, 2, {['3'] = 1}}, nvim('eval', 'w:lua'))
+      eq(1, funcs.exists('w:lua'))
+      curwinmeths.del_var('lua')
+      eq(0, funcs.exists('w:lua'))
     end)
   end)