Allow extensions to contribute dynamic submenus

[gjsjohnmurray]

Currently an extension's menu and submenu contributions can only be statically defined in its package.json. At runtime the extension can use context keys it creates via the setContext command together with when clauses to hide its contributed items dynamically. But there are use-cases where the actual items cannot be predefined, and we have to resort to a QuickPick. IMO this results in a poor UX and some accessibility issues because the list of choices does not appear alongside the context menu action which triggered it.

I see two ways of solving this.

A) Allow submenu contents to be computed when the parent menu entry is selected (or perhaps merely focused).

I outlined this in #9827 (comment)

B) Add a setSubmenuContents equivalent to the existing setContext command.

Using this approach an extension would run the new command, specifying the id of one of the submenus it had defined in its settings.json, plus a second command argument containing the new definition of the submenu.

[gjsjohnmurray]

ping @DanTup @eamodio who may be interested, based on other issues I have reviewed.

[gjsjohnmurray]

Also pinging @Blaiski @larshp @gautier-lefebvre @erythana @yubaoquan @joaomoreno in case you want to 👍 this issue to try and get it into Backlog. Remember, do that on the original issue above, not on this comment.

[DanTup]

Is this the same as #27536? There are definitely many places I'd like dynamic menus (though not just sub-menus - for example on custom tree nodes). One argument against them in the past was making context menus slow (by doing async work), though I think in all my cases I could provide the commands up-front, just not statically (for example at the time I provide a tree node).

[xiaosu12138]

Another +1 from me too. I need to contribute dynamic submenus include menu title according to my setting.json in VS Code

[michaeljones]

I have a scenario of adding a submenu to a tree view item. view/item/context entries for the tree view item can use the viewItem as additional content to enable or disable certain entries. When creating a submenu from the tree view item, it seems like the viewItem is not available in when expressions on items in the submenu. Is that true? If so, could that be addressed? I could make a separate ticket.

[MaxKless]

@gjsjohnmurray are there any news on this?
It's been in the backlog for 2 years... I'd be happy to try and contribute this but would love some feedback first to make sure i'm not wasting my time.

[gjsjohnmurray]

@MaxKless I am not aware of any news. I am a contributor but not a member of the core team, but my hunch is they would want to do this themselves if it ever happens.

[MrYZhou]

I implemented a button by configuring contribution points, and it functions properly.

But the configuration of my button is quite unique. There are quite a few possibilities. I must and can only make judgments in the code. So I have no way now. Because the official API does not have any places to support it. What shall I do? I don't need particularly complex functions. Just like
The custom method like 'vscode. window. create Status Bar Item' is very good

[yiliang114]

The current menus cannot be contributed dynamically. I first have to know all the menus lists and then display them conditionally through when. There are actually many scenarios where the list of menus I need to render is obtained through the asynchronous interface, and the implementation I don't know exactly how many and which menus need to be registered.