Make pallet Assets instantiable

[olanod]

As mentioned in paritytech/polkadot-sdk#327, making the assets pallet instantiable allows one to better group sets of assets that share something in common instead of putting everything in a single big group that might require some sort of filtering on the pallets that depend on some fungibles.

[shawntabrizi]

@olanod asset creation is permissionless, so i don't see how such organization you are striving for will be enforced.

Do you have a more concrete idea on how you want to use this stuff?

[olanod]

But it also can be permissioned only right? At least some of the assets in our chain will be created only by an authority i.e. a set of valid collaterals for a given stable coin. Also I'm looking into assets pallet mostly as an implementor of the fungibles::* traits and not much for its own dispatchable calls.

[shawntabrizi]

@olanod no, it is current not possible to make it permissioned without some sort of wrapper on what functions can be called:

https://github.com/paritytech/substrate/blob/master/frame/assets/src/lib.rs#L368

[olanod]

@shawntabrizi but that's fine no? I can have that wrapper as an extra pallet or a proxy that filters calls and still benefit from the instantiability of Assets pallet. I would say it's even more compelling to have different instances in this case, say I have one instance with some access control filter for cool people only and another one that is general purpose.

[shawntabrizi]

@olanod please take a look at the diff that github provides. We do not use spaces in Substrate, so please update them to tabs. Otherwise the changes look reasonable.

[olanod]

My bad ... will have to disable the format on save 😅

[shawntabrizi]

@thiolliere can you take a quick look here?

[olanod]

The easiest way I found to revert the spaces formatting was to format again overriding the hard_tabs setting of rustfmt, rustmt has a lot of opinions on how the code should look like but as its not the scope of the PR I tried to leave out as much of the extra formatting that was not directly related to the feature as possible splitting chunks as far as git add --patch --interactive allowed me but there might be a bit of formatted code left here and there that I hope you wont mind(and might be for the best).

[gui1117]

ah I forgot, benchmarks need to be updated too, right now benchmark are only generated for default instance not for other ones.

diff --git a/frame/assets/src/benchmarking.rs b/frame/assets/src/benchmarking.rs
index 227d45623d..d02fe7b74b 100644
--- a/frame/assets/src/benchmarking.rs
+++ b/frame/assets/src/benchmarking.rs
@@ -135,7 +135,7 @@ fn assert_event<T: Config>(generic_event: <T as Config>::Event) {
        }));
 }
 
-benchmarks! {
+benchmarks_instance_pallet! {
        create {
                let caller: T::AccountId = whitelisted_caller();
                let caller_lookup = T::Lookup::unlookup(caller.clone());

But there will be other changes inside the file

[shawntabrizi]

@thiolliere check again?

[gui1117]

looks good to me

[gui1117]

bot merge

[ghost]

Trying merge.

[olanod]

Awesome! thanks @shawntabrizi was delaying that for the weekend 👍🏽