Use SpyderWidgetMixin API to build toolbars and menus

* Consistently use add_item_to_menu() and add_item_to_toolbar() to add
  items to menus and toolbars.
* Use sections to add separators to menus and toolbars.
* Define constants for the names of actions, widgets, etc in enum-like
  classes.
* A few minor improvements to code style.

spyder/api/widgets/mixins.py

@@ -168,8 +168,11 @@ def create_stretcher(self, id_=None):
             stretcher.ID = id_
         return stretcher
 
-    def create_toolbar(self, name: str,
-                       register: bool = True) -> SpyderToolbar:
+    def create_toolbar(
+            self,
+            name: str,
+            register: bool = True
+    ) -> SpyderToolbar:
         """
         Create a Spyder toolbar.
 
@@ -184,7 +187,8 @@ def create_toolbar(self, name: str,
         toolbar.setStyleSheet(str(PANES_TOOLBAR_STYLESHEET))
         if register:
             TOOLBAR_REGISTRY.register_reference(
-                toolbar, name, self.PLUGIN_NAME, self.CONTEXT_NAME)
+                toolbar, name, self.PLUGIN_NAME, self.CONTEXT_NAME
+            )
         return toolbar
 
     def get_toolbar(self, name: str, context: Optional[str] = None,

spyder/plugins/variableexplorer/widgets/arrayeditor.py

@@ -43,9 +43,12 @@
 from spyder.py3compat import (is_binary_string, is_string, is_text_string,
                               to_binary_string, to_text_string)
 from spyder.utils.icon_manager import ima
-from spyder.utils.qthelpers import add_actions, keybinding, safe_disconnect
+from spyder.utils.qthelpers import keybinding, safe_disconnect
 from spyder.utils.stylesheet import AppStyle, MAC
 
+# =============================================================================
+# ---- Constants
+# =============================================================================
 
 class ArrayEditorActions:
     Copy = 'copy_action'
@@ -56,6 +59,16 @@ class ArrayEditorActions:
     ToggleBackgroundColor = 'toggle_background_color_action'
 
 
+class ArrayEditorMenus:
+    Options = 'options_menu'
+
+
+class ArrayEditorWidgets:
+    OptionsToolButton = 'options_button_widget'
+    Toolbar = 'toolbar'
+    ToolbarStretcher = 'toolbar_stretcher'
+
+
 # Note: string and unicode data types will be formatted with 's' (see below)
 SUPPORTED_FORMATS = {
     'single': '.6g',
@@ -105,10 +118,10 @@ class ArrayEditorActions:
 LARGE_NROWS = 1e5
 LARGE_COLS = 60
 
-
 #==============================================================================
-# Utility functions
+# ---- Utility functions
 #==============================================================================
+
 def is_float(dtype):
     """Return True if datatype dtype is a float kind"""
     return ('float' in dtype.name) or dtype.name in ['single', 'double']
@@ -127,8 +140,9 @@ def get_idx_rect(index_list):
 
 
 #==============================================================================
-# Main classes
+# ---- Main classes
 #==============================================================================
+
 class ArrayModel(QAbstractTableModel, SpyderFontsMixin):
     """Array Editor Table Model"""
 
@@ -539,7 +553,7 @@ def resize_to_contents(self):
     def setup_menu(self):
         """Setup context menu"""
         self.copy_action = self.create_action(
-            name=None,
+            name=ArrayEditorActions.Copy,
             text=_('Copy'),
             icon=ima.icon('editcopy'),
             triggered=self.copy,
@@ -549,14 +563,17 @@ def setup_menu(self):
         self.copy_action.setShortcutContext(Qt.WidgetShortcut)
 
         edit_action = self.create_action(
-            name=None,
+            name=ArrayEditorActions.Edit,
             text=_('Edit'),
             icon=ima.icon('edit'),
             triggered=self.edit_item,
             register_action=False
         )
+
         menu = self.create_menu('Editor menu', register=False)
-        add_actions(menu, [self.copy_action, edit_action])
+        for action in [self.copy_action, edit_action]:
+            self.add_item_to_menu(action, menu)
+
         return menu
 
     def contextMenuEvent(self, event):
@@ -766,24 +783,31 @@ def do_nothing():
 
         # ---- Toolbar and options menu
 
-        options_menu = self.create_menu('Options menu', register=False)
+        options_menu = self.create_menu(
+            ArrayEditorMenus.Options,
+            register=False
+        )
         options_menu.add_action(self.toggle_bgcolor_action)
         options_menu.add_action(self.format_action)
 
         options_button = self.create_toolbutton(
-            name='Options toolbutton',
+            name=ArrayEditorWidgets.OptionsToolButton,
             text=_('Options'),
             icon=ima.icon('tooloptions'),
             register=False
         )
         options_button.setPopupMode(QToolButton.InstantPopup)
         options_button.setMenu(options_menu)
 
-        toolbar = self.create_toolbar('Editor toolbar', register=False)
-        toolbar.add_item(self.create_stretcher(id_='stretcher'))
-        toolbar.add_item(self.resize_action)
-        toolbar.add_item(self.refresh_action)
-        toolbar.add_item(options_button)
+        toolbar = self.create_toolbar(
+            ArrayEditorWidgets.Toolbar,
+            register=False
+        )
+        stretcher = self.create_stretcher(ArrayEditorWidgets.ToolbarStretcher)
+        for item in [stretcher, self.resize_action, self.refresh_action,
+                     options_button]:
+            self.add_item_to_toolbar(item, toolbar)
+
         toolbar._render()
 
         # ---- Stack widget (empty)