Mismatch in function documentation and observed behavior for DecCoin.MulDecTruncate function

[spoo-bar]

Summary of Bug

Function comment documentation for MulDecTruncate (for DecCoin ) says if multiplier d is zero, it should panic.
However, that is not the observed behavior. Currently nil is returned.

cosmos-sdk/types/dec_coin.go

Lines 375 to 379 in 7c19434

	// MulDecTruncate multiplies all the decimal coins by a decimal, truncating. It
	// panics if d is zero.
	//
	// CONTRACT: No zero coins will be returned.
	func (coins DecCoins) MulDecTruncate(d Dec) DecCoins {

Version

v0.43

Steps to Reproduce

Pass in parameter d value as sdk.NewDec(0)

Or

Test case # 1 tests for this scenario

cosmos-sdk/types/dec_coin_test.go

Lines 885 to 888 in 7c19434

	{"Multiple coins - zero multiplier", sdk.DecCoins{
	sdk.DecCoin{testDenom1, sdk.NewDecWithPrec(10, 3)},
	sdk.DecCoin{testDenom1, sdk.NewDecWithPrec(30, 2)},
	}, sdk.NewDec(0), sdk.DecCoins(nil), false},

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For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned

[evancholmberg]

I would like to work on this issue. I see that there is a comment above the test that states it needs to be fixed. So the behavior of the function needs to change to panic when multiplier d is zero and the test needs to change to expect a panic?

[alexanderbez]

I would like to work on this issue. I see that there is a comment above the test that states it needs to be fixed. So the behavior of the function needs to change to panic when multiplier d is zero and the test needs to change to expect a panic?

Yes :)