vscode: Deserialize function doesn't have uri parameter

I am working on getting Live Share notebooks functional again after recent API changes. We want Live Share notebooks to be running on stable APIs, which means using serializers rather than content providers.

However, serializers do not work for the guest scenario. Previously, the guest’s content provider would have an openNotebook function with a uri parameter for the document being opened. We proxied that request to the host, where we could use vscode.notebook.openNotebookDocument with the uri. Now, deserialize only includes the document’s content. I can add the serializer’s view type to proxied request, but the only information we can give the host is content and viewtype. We need it to return NotebookData, but we cannot identify which notebook document to deserialize.

Could vscode.commands.executeCommand('_resolveNotebookContentProvider'); return serializers that have callable deserialize functions?

cc @jrieken @rebornix @davsterl