Inconsistent Limit in InfiniteGasMeter

[ethanfrey]

Summary of Bug

Limit() on InfiniteGasMeter always returns 0: https://github.com/cosmos/cosmos-sdk/blob/master/store/types/gas.go#L148-L150

This is not true and causes issues in code that check for Limit before performing an action: CosmWasm/wasmd#539 (review)

The main point being there is no clear way to determine how much gas is left in the meter. Maybe you could expose a separate function to return that info. But, just returning max.Uint64 for infiniteGasMeter.Limit() would be a good start.

Version

v0.42.6, master, probably every other known version

Steps to Reproduce

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[fedekunze]

Agree that this is very confusing, I guess that's why the ConsumedToLimit function was implemented in the first place

[ethanfrey]

That says how much was consumed, not how much was left.

We need to use this remaining gas as a limit in wasmer for the smart contracts. And have to special case limit == 0 only as we know the implementation of InfiniteGasMeter, which is fragile

[alexanderbez]

For the time being, can you just check the type of the gas meter and not execute calls to Limit in cases where it's an InfiniteGasMeter?