Sort MultiAssets on extrinsic submission

[KiChjang]

As it was found out in paritytech/cumulus#892, extrinsics will fail if the MultiAssets parameter is not properly sorted. We should then ensure that the frontend UI sorts the Vec on submission.

[jacogr]

It is very unlikely to be done in the UI itself - the extrinsics builder is completely generic and has no idea as to what it actually submits. There really is no transaction logic in there.

If done via modals, then yes, it needs to always work so anywhere where txs are constructed with the UI dev help (via modal where the params are fixed), it makes sense.

If the request is for the extrinsics page, that would need to happen on the API layer. (BTreeMap is likewise required to be sorted and done on that level)

[KiChjang]

I just remembered that there's also one important detail for the teleport_asset or reserve_transfer_asset extrinsics -- the 4th parameter is fee_asset_item, which is an index of the assets vec that indicates which asset in the vec is used to pay for the weights.

If we haphazardly reorder the assets vec, we'd invalidate this index, and so I think the better solution here may just be to create new UI elements specifically for these two extrinsics. I'm not sure if this is a cleaner way though, I could be wrong.

[jacogr]

Good point that I didn't think of.

PS: Bonus point for using "haphazardly" in this context, it made my morning

[jacogr]

Closing, cannot really be done on the API - it is types agnostic. (Not sure if the UI wants this either, since it "just displays and doesn't interpret", but that is up to that layer)

[polkadot-js-bot]

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