func (vm *VM) IBCPacketReceive consistency

[webmaster128]

Analogue to to the other IBC functions in lib.go, IBCPacketReceive should return an IBCReceiveResponse instead of IBCReceiveResult as the first return value. This basically reverts c300106.

Currently wasmd requires special error handling to handle both error types: https://github.com/CosmWasm/wasmd/blob/c7670fae4e6ca24d7fd6bfa6768f166b36976432/x/wasm/keeper/relay.go#L135-L137

A more straight forward way to do this adding this back to wasmvm:

	if resp.Err != "" {
		return nil, gasUsed, fmt.Errorf("%s", resp.Err)
	}
	return resp.Ok, gasUsed, nil

Now in order to allow wasmd to get full access to the error returned by the contract, we can use a dedicated error type for that case.

[webmaster128]

The other (maybe simpler) option is to always return the inner result to wasmd

[alpe]

The error handling in wasmd is going to be modified in CosmWasm/wasmd#1220 to handle resp.Err and errors returned to the function call differently. Therefore the current api in wasmvm makes sense so that we can separate the different cases and provide a simple way for contract developers to create error ACKs.

[webmaster128]

Therefore the current api in wasmvm makes sense so that we can separate the different cases and provide a simple way for contract developers to create error ACKs.

Right. Then we should always return the result for the other APIs at the same level for consistency. wasmd can then handle the cases separately or just turn the error result in an error.

[alpe]

For all other IBC methods we do not have 2 different error scenarios with different db transaction behaviour. IMHO we should accept that IBCPacketReceive is different and not make everything equal.
Is there a simple way to communicate this in code and doc better?