Support for updatable/async menus and submenus

[testforstephen]

In Java extension, we often receive feedback from users that refactoring and source action features are missing even though these features exist under these menus. We're thinking if there is a way to improve feature discovery for them.

Currently, users must click on the editor's context menu "Refactoring..." and "Source Action..." to display the supported options, which is not visible to new users. To improve visibility, one suggestion is whether VS Code could automatically expand their submenus when the cursor hovers over them.

[jrieken]

As of today we have no support for lazy menus. Those would be required because at the time of clicking "Refactor" we don't know what refactorings are available. We need to do an async IPC call for that and therefore cannot draw submenu.

We have a custom menu that could support this and I have seen this in native macOS app but I don't know if this is doable with electron. Forwarding to menu folks

[jrieken]

Being able to update a menu while it shows should be enough. We would show "Loading..." and later update the menu in-place. I assume that's the min-requirement to get this working

[sbatten]

I don't see anything on the electron side that would let us support this https://www.electronjs.org/docs/latest/api/menu-item

[deepak1556]

Upstream issue electron/electron#24724

[joyceerhl]

@sbatten could we use Electron's menu.append(menuItem) API to support asynchronously adding menu items to a context menu that's already been drawn? https://www.electronjs.org/docs/latest/api/menu#menuappendmenuitem menu.insert(pos, menuItem) also seems promising for updating items which have changed.

[deepak1556]

@joyceerhl the menu append calls do not update the menu while being drawn the changes get reflected in subsequent draw calls, previously linked upstream issue is incorrect, the correct one is electron/electron#528