Best practise for maintaining document state on a language server?

[ainslec]

This is not an issue, so feel free to close this down and direct me to the correct forum for questions, but I have a question regards the tracking of document state by the language server.

I have attached some message listeners to the LSP and see that text deltas are being sent by the protocol correctly. But my question is what is the general mechanism for handling document state on the server side. I would have assumed (in my ignorance) that each time a document was switched on a client that a full version of the document would be supplied to the server, and as the foreground document (of the active window) was edited, the deltas would be supplied. But, by observing the protocol, it seems that only opening of a document on a client will send the initial document, then potentially you could have 1,000 documents open on the client at the same time, and the server must be ready to apply deltas (assuming that the text document synch kind is set to incremental - which I like).

So, is the server meant to maintain state for every opened document, or is there a way for a server to ask for a complete version of a document state when documents are switched (so that only one active document requires its state tracking on the server)?

I'm just trying to figure out best practise for maintaining state. My apologies if this is (and likely is) the wrong place to ask this question, or for not understanding the spec well enough.

[felixfbecker]

The server should maintain content state between textDocument/open and textDocument/close calls. There is currently no way to read document content of arbitrary files through LSP, so you can either read from disk or use an LSP extension (in environments where you can't access the disk): https://github.com/sourcegraph/language-server-protocol/blob/master/extension-files.md

[dbaeumer]

@felixfbecker explanation is correct. However we do have requests to allow servers to fetch the content of a document from the client so that the server could skip open documents.

I will close this issue as a question.