Investigate: can the tip type be detected via metadata or Runtime?

[haerdib]

Currently, it has to be manually chosen which type of tips are used in the runtime (AssetTip, PlainTip). That's a hassle. Shouldn't it be possible to determine that via the metadata?

[haerdib]

Or maybe via Runtime (via PR #340) as Rust does not like type determination during runtime.

[haerdib]

I have investigated a little - and got to the following result:

• I think, it is not possible to deduct the Tip type via the Runtime. The AdditionalSigned is too generic. However, it is possible to get the SignedExtensions type from the Runtime:

pub struct SignedExtraWrapper<Runtime>
where
	Runtime: GetRuntimeBlockType + frame_system::Config,
	<Runtime::RuntimeBlock as Block>::Extrinsic: ExtrinsicMetadata,
{
	pub extra: <<Runtime::RuntimeBlock as Block>::Extrinsic as ExtrinsicMetadata>::SignedExtensions, 
	//  ^^^ That's the Extra which implements the Trait SignedExtension, e.g. the function:
	fn additional_signed(&self) -> Result<Self::AdditionalSigned, TransactionValidityError>;
}

And that might be enough. The compose macors would need to be adapted.

• Getting the Tip Type via metadata might be possible. What's certainly possible though, is retrieving the AddtionalSigned type, with the SignedExtensionMetadatatype.

Useful substrate locations:

• https://github.com/paritytech/substrate/blob/master/primitives/runtime/src/traits.rs#L1056
• https://github.com/paritytech/substrate/blob/master/primitives/runtime/src/generic/unchecked_extrinsic.rs

[haerdib]

Related issue : paritytech/substrate#12929

Via metadata (V14) it can be detected if the pallet_asset_tx_payment is imported into the runtime. And I believe, with quite some certainty, one can say if that's the case, then the fees will be paid with that pallet and so will the tips be. But I guess that not 100% sure, because one could simply define that pallet but not use it at all.
This might be better once V15 is published.

Conclusion: I think it's not worth to invest too much time to this. Let's wait for V15 and hope for a better world. If that takes too long, #406 might be a reasonable solution.

[clangenb]

You can't because encointer does not use the pallet_asset_tx_payment, but we use CommunityIdentifier as asset id, which is not exposed in the metadata AFAIK.

[haerdib]

Happy news: Metadata v15 incoming soon! (checkout: paritytech/substrate#13287) 🥳