cargo-contract exits on event decoding failure

[pmikolajczyk41]

Problem statement

As for now, after submitting a transaction to a chain (either call, upload or instantiate) cargo contract listens for events and decodes them. In particular, every event that comes from any contract is decoded using the metadata file corresponding to the 'entry' contract. In case of any failure, the error is propagated up to the user, which cause the whole program to exit and fail.

Such a situation is easily reproducible with any pair of contracts A and B, such that:

• A calls B
• B emits an event E
• E is not compatible with A's metadata (it is sufficient that A doesn't declare any events)

This happens often in any non-trivial dApp and thus makes using cargo-contract impossible to deploy and interact with more interesting examples.

Relevant code

https://github.com/paritytech/cargo-contract/blob/master/crates/cargo-contract/src/cmd/extrinsics/events.rs#L110

Suggested solution

In case of decoding failure, we should just log warning / info that the event couldn't have been properly decoded with provided metadata and just continue.