Listener API

[bollwyvl]

A number of issues (#95, #17, probably more) have identified a need for writing
concrete files to disk in order for language servers to act on them. This is
sufficient to start the conversation about allowing the pipeline of language
messages to be intercepted by any number of agents. Currently the flow looks like:

                 --> queue --> stdin
                |                |
                |                v
client  <--> handler         language server
                ^                |
                |                v
                 --  queue  <-- stdout

Proposed is to allow any number of listeners to react to the messages.

                 --> listener --> queue --> stdin
                |                            |
                |                            v
client  <--> handler                   language server
                ^                            |
                |                            v
                 --  listener <-- queue <-- stdout

Not proposed is to actually change or prevent the delivery of messages,
nor to encourage direct access to the handlers or servers, but rather to delay
delivery of a message until some external side effect has been completed, in the
initial case, the writing of a file to disk.

This particular case could be achieved through direct use of the existing
ContentsManager API, but in this case, LSP provides a change-based approach
over WebSockets that is likely more performant.

notional API

from jupyter_lsp import on_lsp_message, LanguageServerManager

def load_jupyter_server_extension(nbapp):
    # another extension developer might need to IOLoop.call_later
    mgr = nbapp.language_server_manager

    @on_lsp_message(languages=".*", methods=r"textDocument/did(Open|Close)")
    async def do_thing_with_message(
        message: LSPMessage, 
        manager: LanguageServerManager
    ) -> None:
        # do something with a message

As these cannot change the message, they can be scheduled to run in "parallel".

notional manager changes

import asyncio

class LanguageServerManager
    async write_server_message(message, language):
        await asyncio.gather([
            listener(message, self)
            for listener in listeners
            if listener.should_listen(message, {"language": language})
        ])
        for session in self.get_sessions(language):
            await session.write_message(message)

[krassowski]

I guess we can close this one?

[krassowski]

Please reopen if needed!

[bollwyvl]

Oops, yes, thanks. We'll learn more as people think of things to do with it. Probably need to expose a client-side one, too, at some point...

…

On Tue, Jan 14, 2020, 18:35 Michał Krassowski ***@***.***> wrote: Closed #99 <https://github.com/krassowski/jupyterlab-lsp/issues/99>. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <https://github.com/krassowski/jupyterlab-lsp/issues/99?email_source=notifications&email_token=AAALCRG3DWEHHOPVRN4TTSDQ5ZD2RA5CNFSM4JKAO3LKYY3PNVWWK3TUL52HS4DFWZEXG43VMVCXMZLOORHG65DJMZUWGYLUNFXW5KTDN5WW2ZLOORPWSZGOV7DCRHQ#event-2948999326>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAALCRENQTZCFZNFGKUBMN3Q5ZD2RANCNFSM4JKAO3LA> .