Add some info for testing(in general) the extensions built on tower-lsp

[Hyperion101010]

Hi there, at hyperledger we are developing vscode server for solidity language and tower-lsp has proved as a great server implementation to built our server on. Thanks for writing this server and for keeping it up to date.
So I was working on my version of the server and finished implementing the hover feature for same. Now my server is in Rust(tower-lsp) and the client is in Js. I searched on the vscode API but I couldn't find any way to invoke hover while running tests(like running test from client side and getting the hover message in the test from the server using some function).
I implemented diagnostics as well but at that time vscode API had getdiagnostics function which did the trick. This time I can't find any such method for hover.
Any suggestions on how should the hover tests be implemented?
my repo: https://github.com/hyperledger-labs/solang-vscode

[silvanshade]

Any suggestions on how should the hover tests be implemented?

@Hyperion101010 One possibility would be to test textDocument/hover in a similar way to how I do for wasm-lsp/wasm-language-server. See here. Specifically, the actual responses from the server are checked here.

[ebkalderon]

@Hyperion101010 Hello! Thank you for the kind words; I'm glad to hear that tower-lsp has been useful to you. LspService implements the tower::Service trait and is therefore compatible with the broader Tower ecosystem, including tower-test which is used to test Tower-based libraries. In essence, LspService can be conceptually modeled as the function below (see the actual Service implementation on docs.rs):

async fn call(&mut self, req: Incoming) -> Result<Option<Outgoing>, ExitedError>

One can leverage tower-test to spin up an instance of the language server in tests, send requests, and assert the content of responses like this:

tower-lsp/src/service.rs

Lines 177 to 233 in 58457ad

	#[tokio::test]
	async fn initializes_only_once() {
	let (service, _) = LspService::new(|_| Mock::default());
	let mut service = Spawn::new(service);
	let initialize: Incoming = serde_json::from_str(INITIALIZE_REQUEST).unwrap();
	let raw = r#"{"jsonrpc":"2.0","result":{"capabilities":{}},"id":1}"#;
	let ok = serde_json::from_str(raw).unwrap();
	assert_eq!(service.poll_ready(), Poll::Ready(Ok(())));
	assert_eq!(service.call(initialize.clone()).await, Ok(Some(ok)));
	let raw = r#"{"jsonrpc":"2.0","error":{"code":-32600,"message":"Invalid request"},"id":1}"#;
	let err = serde_json::from_str(raw).unwrap();
	assert_eq!(service.poll_ready(), Poll::Ready(Ok(())));
	assert_eq!(service.call(initialize).await, Ok(Some(err)));
	}
	#[tokio::test]
	async fn refuses_requests_after_shutdown() {
	let (service, _) = LspService::new(|_| Mock::default());
	let mut service = Spawn::new(service);
	let initialize: Incoming = serde_json::from_str(INITIALIZE_REQUEST).unwrap();
	let raw = r#"{"jsonrpc":"2.0","result":{"capabilities":{}},"id":1}"#;
	let ok = serde_json::from_str(raw).unwrap();
	assert_eq!(service.poll_ready(), Poll::Ready(Ok(())));
	assert_eq!(service.call(initialize.clone()).await, Ok(Some(ok)));
	let shutdown: Incoming = serde_json::from_str(SHUTDOWN_REQUEST).unwrap();
	let raw = r#"{"jsonrpc":"2.0","result":null,"id":1}"#;
	let ok = serde_json::from_str(raw).unwrap();
	assert_eq!(service.poll_ready(), Poll::Ready(Ok(())));
	assert_eq!(service.call(shutdown.clone()).await, Ok(Some(ok)));
	let raw = r#"{"jsonrpc":"2.0","error":{"code":-32600,"message":"Invalid request"},"id":1}"#;
	let err = serde_json::from_str(raw).unwrap();
	assert_eq!(service.poll_ready(), Poll::Ready(Ok(())));
	assert_eq!(service.call(shutdown).await, Ok(Some(err)));
	}
	#[tokio::test]
	async fn exit_notification() {
	let (service, _) = LspService::new(|_| Mock::default());
	let mut service = Spawn::new(service);
	let initialized: Incoming = serde_json::from_str(INITIALIZED_NOTIF).unwrap();
	assert_eq!(service.poll_ready(), Poll::Ready(Ok(())));
	assert_eq!(service.call(initialized.clone()).await, Ok(None));
	let exit: Incoming = serde_json::from_str(EXIT_NOTIF).unwrap();
	assert_eq!(service.poll_ready(), Poll::Ready(Ok(())));
	assert_eq!(service.call(exit).await, Ok(None));
	assert_eq!(service.poll_ready(), Poll::Ready(Err(ExitedError)));
	assert_eq!(service.call(initialized).await, Err(ExitedError));
	}
	}

Note that a less-than-pretty caveat of the current design is that server-to-client requests (initiated by calls to Client) are sent through a separate channel (the MessageStream returned by LspService::new()) and will have to be asserted separately.

This may change in the future with #177, where LspService is remodeled to avoid this problem, which will undoubtedly be a breaking change to any downstream testing code. Feel free to contribute further there if you have something to share!

[ebkalderon]

I think this issue should be safe to close if it can be confirmed that tower-test satisfies the needs of your language server project. But if enough users are asking the same question, though, perhaps we could clarify things further and add a helpful section to the README explicitly pointing users to the tower-test documentation. 😄

[Hyperion101010]

Sure, I will checkout the details. Closing this issue.

[ebkalderon]

Feel free to reopen if you run into troubles with tower-test, @Hyperion101010. Thanks for reporting this issue!

[lpil]

Could we open this issue to track adding testing documentation? Thank you

[ebkalderon]

Sure, @lpil! I can amend the README to include a link to tower-test.