Make switching between external reference-view and internal reference-view more feasible

[CsCherrYY]

TL;DR

See the Requests section.

Background

Currently, vscode-java supports Type Hierarchy in its own way (not standard LSP) and use the reference-view API to show the result. Since Type Hierarchy has been supported in vscode, reference-view and language-client, we are trying to migrate our current implementation to LSP based and there is a PR in progress.

About the implementation in reference-view, we had a discussion in #126666. Now we can successfully migrate our UI implementation of supertype and subtype view to the [type hierarchy implementation] (https://github.com/microsoft/vscode-references-view/tree/main/src/types) in reference-view. However, for vscode-java, there is an extra Class Hierarchy view is not supported in reference-view and LSP. We want to implement it ourselves via reference-view API and find some gaps here.

Gaps

We can successfully register our own Class Hierarchy view and show it.

You can see we can switch to other view in vscode-java current implementation. either in the view title or in the item menu.

When migrating to LSP implementation, we encounter some difficulties in switching the Class Hierarchy view (implemented in vscode-java) and the Supertype/Subtype Hierarchy view (implemented in reference-view).

Switch from Class Hierarchy view (in vscode-java) to Supertype/Subtype Hierarchy view (in reference-view)

We need to execute command references-view.showSupertypes or references-view.showSubtypes to switch the view. We can offer the right location as an anchor, but the current implementation only receives TypeItem | unknown. We'd like to change this behavior to accept a vscode.Location as an anchor as well. (Actually, all we need here is the location)

Switch from Supertype/Subtype Hierarchy view to Class Hierarchy view

We can call our constructors to create a new Class Hierarchy view, but we don't have the current anchor information from current reference-view. The reference-view API only exposes setInput() method. If there is any api like getInput(): SymbolTreeInput then we can get the current anchor via SymbolTreeInput.location.

Requests

1. Make the implementation of setTypeHierarchyDirection() accepts a vscode.Location as its parameter anchor as well.
2. Add a new API

getInput(): SymbolTreeInput<unknown>;

on the opposite side of current setInput().

@jrieken do you think it make sense? If so, I can create corresponding PRs in the reference-view repository.

[CsCherrYY]

@jrieken I found the references-view repo has been archived. Should I create the related PRs in vscode repo?