claim_assets doesn't work if the trapped asset can't be used to pay for execution fees.

[franciscoaguirre]

The claim_assets extrinsics claims in the simplest way possible, it just grabs the asset, uses it to pay execution fees, and deposits it on the beneficiary account.
This assumes the asset can be used to pay for fees, which might not be the case, i.e. an NFT or a fungible token without a pool.

The extrinsic creates the following program:

• ClaimAsset
• BuyExecution // <- Here's the assumption the asset can be used to pay for fees
• DepositAsset

It could be fixed by changing that to the following program:

• WithdrawAsset(asset for fees)
• BuyExecution // <- No longer assuming the trapped asset can be used to pay for fees
• ClaimAsset
• DepositAsset

We could probably pass in a fees parameter that could be None to use the same assets for fees.
Sadly, this would be a breaking change.
We could add a new extrinsic claim_assets_with (or claim_not_sufficient_assets) that takes this fees parameter (not necessarily an option since we already have the other extrinsic).

[dogwifdots]

Woof, just found this while researching for an upcoming token claimable airdrop for DOT holders that Dog wif dots (WIFD) is planning. Could I use this function for an embedded extrinsic function on our website to web3 login and click a claim your WIFD button to start the TX signature in the users wallet?

Many thanks in advance,
Dog wif dots dev

[franciscoaguirre]

@dogwifdots This extrinsic is for claiming assets trapped during XCM execution. It's useful to get back your assets when an error occured. It's not for airdrops.