Support for converting IBCEvent into abci::Event

[adizere]

Crate

ibc

Summary

Currently, there is no way to transform an IbcEvent into the corresponding tendermint::abci::Event.

Context

Why do we need this feature?

This feature is necessary for being able to test integration of the ibc crate against Hermes. More concretely, for this kind of test, the complete path of execution is as follows:

1. relayer calls send_msgs to submit a batch of transactions to a chain, and expects as a response a Vec<IbcEvent>:

https://github.com/informalsystems/ibc-rs/blob/d5ba86d182a8cc488f3dd500408bdde320db11be/relayer/src/chain.rs#L108

2. the chain processes these transactions by calling into our ibc modules, which produce IbcEvent types upon delivering a set of transactions.

3. the ABCI interface of a Tendermint chain should produce abci::Event types (not IbcEvent). The present issue covers this step of translating IbcEvent into abci::Event.

4. the chain responds to the relayer with a vector of abci::Event. The relayer then translates these into IbcEvent which it can continue processing.

Question

Notice that there is a redundant step in the execution above: produce IbcEvent (step 2), translate into abci::Event (step 3), translate back into IbcEvent (step 4). It is not clear if we can avoid this double conversion.

Acceptance Criteria

There are two parts to this issue:

1. clarify if we can avoid the double conversion problem.
2. if we cannot avoid the redundancy in conversion, then add a method

pub fn from_event(e: &IbcEvent) -> Option<tendermint::abci::Event>

probably somewhere in ics02_client/events.rs.

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[ancazamfir]

Found this while looking at informalsystems/hermes#1375. What is the concrete usecase for converting IBC events into abci events?

[adizere]

I think the idea is to make an ibc-rs chain (e.g., basecoin-rs) capable of generating events out of executed transactions, so that it can send these events to Hermes (via websocket). Then we can have an integration test that covers the entire feedback loop between basecoin-rs and Hermes, allowing to test the start command.

[ancazamfir]

So basecoin-rs chain generates the transactions? In what format are the transaction events?

[hu55a1n1]

basecoin-rs (upon receipt of hermes tx raw {create-client | update-client}) calls into the IBC routing module's dispatch() which generates IBCEvents:
https://github.com/informalsystems/basecoin-rs/blob/phase3/src/app/modules/ibc.rs#L438-L445

And here's the code that converts these events to ABCI Events that can be returned to tendermint:
https://github.com/informalsystems/basecoin-rs/blob/phase3/src/app/modules/ibc.rs#L477-L501

[yito88]

I didn't know this issue before trying my implementation!
I have added the conversion for IbcEvent to abci::Event at informalsystems/hermes#1430.

I'd like to add this conversion so that a chain can emit an IBC event including specified attributes for each event.