Extension API for VS Code v1

[FunkMonkey]

Description

This is a PR for #1041. It is as simple as possible, basically exporting the VsCodeExtension instance to be usable by other extensions.

This could for example be used to directly communicate with the models (e.g. via model.streamChat etc.) or to communicate with the chat webview, for example:

continueInstance.webviewProtocol.request("userInput", {
  input: "Please do X for me!",
});

I believe it is currently ok to export the VsCodeExtension instance, despite giving full access to internals of continue, in order to figure out what features are actually useful for other extension authors. Later on, the instance property should be deprecated in favor of a better designed external API.

Maybe the author of #803 could make use of this simple API, too, instead of adding the proposed functionality to continue itself.

For a better Typescript experience, the types of the API should also be exposed as an npm package.

Checklist

• The base branch of this PR is preview, rather than main

[sestinj]

@FunkMonkey I'm going through all of the many PRs that have ended up on the back burner, and I realize now that I completely missed this. The principle I think we're coming to is that it's not best to accept "input" from other extensions. What I mean by this is that you could do something like registering a custom "slash command" or "context provider" (like here), but we don't want to allow arbitrary usage of Continue resources without the user triggering them. Especially when something like OAuth is in place to allow users to access resources from an account, this could pose a potential security risk.

I'm going to close this PR because of this, but I would be curious to hear in the GH issue whether you think that there might be another way of accomplishing what you're looking to do. Hope to hear from you, and hopefully we can make something work!