crisis/invariant ConstantFee parameter check, and other missing parameters

[jaekwon]

Currently the code silently returns a zero constant fee if one isn't set properly:

+// GetConstantFee get's the constant fee from the paramSpace
+func (k Keeper) GetConstantFee(ctx sdk.Context) (constantFee sdk.Coin) {
+       if err := k.paramSpace.Get(ctx, ParamStoreKeyConstantFee, &constantFee); err != nil {
+               // TODO: return error - needs rewrite interfaces
+               // and handle error on the caller side
+               // check PR #3782
+       }
+       return
+}

We should at least panic here instead of returning a zero fee regardless of the current state of refactoring to return an error (I don't think we should change parameter reads to return an error though, since the run-time expectation is that the parameter exists, return an error just makes the codebase messier).

We also should check somehow during chain init that the parameter exists and is nonzero, otherwise we may forget to set this in the genesis state, and result in a DDoS vector.

---

Update: I found more code with the comment for parameters getting/setting:

+               // TODO: return error - needs rewrite interfaces
+               // and handle error on the caller side
+               // check PR #3782

They should all panic rather than returning silently.

I think they should all have some check to ensure that they exist prior to usage (maybe in initchain, though maybe that isn't possible yet, I'm not sure where this check should happen), and that required parameters should panic rather than error.

[rigelrozanski]

Correct it looks like there are in fact many panic->error which don't make sense introduced in #3782 / here, this error should panic if it's not set properly

[alexanderbez]

Wait, is this blocking v0.34.0? #3782 was never introduced into release/v0.34.0. I opened up a PR against develop that reverts it.

[rigelrozanski]

you're correct, this bug was never introduced in the release 0.34 branch, and must only be reverted on develop