fix: Update fee calc to use system::constants::BlockWeights.per_class.normal.base_extrinsic

[emostov]

closes: #385

For review discussion

Should we take into account DispatchClass when using baseExtrinsic? At the moment polkadot runtimes have the baseExtrinsic for each class is fixed: https://github.com/paritytech/polkadot/blob/cd0e9186a6620aab846a8a54969a0e5bbecbd060/runtime/common/src/lib.rs#L88

From my understanding the changes would roughly require a refactor of the calc_fee.rs logic to do something like take in the dispatch class for each calc_fee() call and pass a mapping of the base_extrinsic weight for each dispatch class when creating CalcFee.from_params().

My two cents is that we should ship this fix ASAP, and then get the more thorough fix out next week.

[athei]

Please keep in mind that this only works for non-normal transactions if they share the same base extrinsic weight.

[kianenigma]

so the js api has the value api.consts.system.extrinsicBaseWeight set before the weight refactor and for a chain that has it, the latter one?

[dvdplm]

If ^^^ is correct it'd be good to annotate the code above with something like "Behaviour changed with substrate PR #6629 (polkadot runtime vX.Y.Z)".

[kianenigma]

Sensible to do as you said:

My two cents is that we should ship this fix ASAP, and then get the more thorough fix out next week.

[dvdplm]

I have a poor understanding on what is going on here, apologies.

I think this change merits a test or two.

[dvdplm]

If ^^^ is correct it'd be good to annotate the code above with something like "Behaviour changed with substrate PR #6629 (polkadot runtime vX.Y.Z)".

[dvdplm]

LGTM; we'll revisit this more thoroughly in subsequent releases.

[emostov]

@TarikGul , @dvdplm , @kianenigma - I just re-did the whole thing. I forgot that the api always uses the latests metadata. If we are doing a query in a historical runtime we need to fetch the old metadata, decorate it, and grab the constant. If we are doing a query in the latest runtime we can save the effort and just use the decorated metadata built into the api. The logic is worth another look over

[emostov]

We are making an assumption here that if a runtime has one of these in the metadata currently, all past runtimes will have it. Since we only support fee calcs on a limited number of chains I think this is ok for now

[dvdplm]

The logic is worth another look over

Still LGTM.