Remove Zero Coins from Parsing

[alexanderbez]

ParseCoins and ParseDecCoins will currently return an error if a zero (dec) coin is provided as input (via the IsValid check). Arguably, it's a better dev UX to simply remove all the zero (dec) coins after parsing/sorting and not return an error.

/cc @jaekwon

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[alessio]

I'd argue that

1. it's legitimate to instantiate a zero-Coin via API
2. unless there's a use case for ParseCoins() to consider a zero input legit (and AFAIK there isn't any), I would not fix it as it's not broken.

Re: it makes sense to not fail on parsing zero (empty) DecCoins as AFAICR we need to parse config file options where supplying 0 is actually a legit value.

[alessio]

How do we about this then @alexanderbez ?

[alexanderbez]

So under further thought, I think allowing zero coins through ParseCoins and simply removing them is not desirable. Doing so would allow zero amount txs to be valid and pass (unless certain checks are added in place). However, ParseDecCoins might be a different case. Perhaps we should allow zero coins to be removed.

[alessio]

Can we parametrise the removal?

func ParseDecCoin(coinStr string, stripZeroes bool) (coin DecCoin, err error)

[alexanderbez]

Yeah, good idea @alessio.

[alessio]

Does ParseDecCoins ever need to fail when the underlying slice is empty? Cause we could parametrise ParseDecCoins as well by adding an extra argument failIfZero

[alexanderbez]

I'm not sure. I'm honestly tempted to just leave as-is unless a demand for it appears.

[alessio]

No demand, no need to do it.