We have RemoteFileService#canHandleResource which was introduced as workaround to be able to restore editors from providers that aren't known (yet) but that were around during the last session: https://github.com//Microsoft/vscode/commit/a23633b5d42dc486a668e49a232957696750c254.

This wasn't designed to be a general purpose API and I am surprised by its popularity. In hindsight the FileEditorInput should have serialised that knowledge about other-schemes and not the file service. I want to make that change but many other references leave me puzzled. This is what's to do

• use canHandleResource in combination with onDidChangeFileSystemProviderRegistrations
• don't rely on this information statically, e.g. expect that scheme come and do and expect that in the beginning there is just the file-scheme