session: allow to borrow the stream mutably

[tzemanovic]

related to #35 - we'd like to be able to get access to the session's stream - we're using it to put a process to a background with https://github.com/anoma/anoma/blob/c17f4f634b14ee2f202ec51c3f9d4eb1a7f996a1/tests/src/e2e/setup.rs#L468 - we found unlike in rexpect, when we run multiple sessions at once and the commands that they run interact with each other in some way, if some session's output is not being processed it gets blocked on it

[zhiburt]

Hi @tzemanovic

Overall I doubt if it's good design to expose TryStream<S>. What could be useful potentially though is to implement AsMut<S> for session.

As I see your use case, you need read_available to be able to fill buffer in an additional thread.

You could just call is_matched(Eof) instead. Also we could expose this function directly on Session.

we found unlike in rexpect, when we run multiple sessions at once and the commands that they run interact with each other in some way, if some session's output is not being processed it gets blocked on it

You mean it blocks because it is slower or because there some output wasn't processed which is unexpected?

we're using it to put a process to a background

See my comment in #35 also related.

[zhiburt]

ping @tzemanovic

[tzemanovic]

@zhiburt thanks again, I'll try to switch to is_matched(Eof)

You mean it blocks because it is slower or because there some output wasn't processed which is unexpected?

I'm not quite sure tbh - in the test case we run e.g. a server in expectrl session and another session with a client, which submits something to the server and we expect it to print something after response from the node. However, the server session is not processing its output (there's no active expect call on it, it's on the client waiting for a reponse) and it seems to block it from processing the client's request

[tzemanovic]

forgot to note - we're using the sync version

[tzemanovic]

is_matched(Eof) works well for our case, so this change is not necessary

[zhiburt]

I'm not quite sure tbh - in the test case we run e.g. a server in expectrl session and another session with a client, which submits something to the server and we expect it to print something after response from the node. However, the server session is not processing its output (there's no active expect call on it, it's on the client waiting for a reponse) and it seems to block it from processing the client's request

Could I run this flow myself? I guess this my be worth to investigate.

[tzemanovic]

Could I run this flow myself? I guess this my be worth to investigate.

Sure, but I have to admit that the project is quite heavy to compile, so it is by no means a minimal example.

From the branch of https://github.com/anoma/anoma/pull/1095, you can make build-wasm-scripts (you might need to install rustup target add wasm32-unknown-unknown first) and then e.g. ANOMA_E2E_KEEP_TEMP=false ANOMA_E2E_DEBUG=true cargo test e2e::ledger_tests::ledger_txs_and_queries -- --test-threads=1 --nocapture (again, you might need some additional dependencies, see https://docs.anoma.net/user-guide/install.html#from-source).

If we remove let _bg_ledger = ledger.background(); in tests/src/e2e/ledger_tests.rs:183 that's been added for this change, then the client gets stuck on the next client.exp_string (line 282).