Relax genesis config to not require Default impl

[nazar-pc]

There wasn't any meaningful "default" for one of the pallets I'm working with, so I looked at why it is required and I didn't find a good reason for that.

[nazar-pc]

Hm, looks like construct_runtime still requires Default implementation on pallet::GenesisConfig for some reason 🤔

[michalkucharczyk]

Hm, looks like construct_runtime still requires Default implementation on pallet::GenesisConfig for some reason 🤔

Can you share more details? (with this env enabled, maybe it will show some more details)?

[nazar-pc]

No, I'm just running cargo clippy --all-targets without FRAME_EXPAND and getting this:

error[E0277]: the trait bound `pallet::GenesisConfig<mock::Test>: std::default::Default` is not satisfied
   --> crates/pallet-subspace/src/mock.rs:70:1
    |
70  | // frame_support::construct_runtime!(
71  | ||     pub struct Test {
72  | ||         System: frame_system,
73  | ||         Balances: pallet_balances,
...   ||
77  | ||     }
78  | || );
    | ||_- in this macro invocation
...   |
    |
    = note: this error originates in the derive macro `Default` which comes from the expansion of the macro `frame_support::construct_runtime` (in Nightly builds, run with -Z macro-backtrace for more info)

[michalkucharczyk]

It originates here:

polkadot-sdk/substrate/frame/support/procedural/src/construct_runtime/expand/config.rs

Line 71 in 76724ce

#[derive(#scrate::__private::serde::Serialize, #scrate::__private::serde::Deserialize, Default)]

Default for sure will be required if the runtime is supposed to support GenesisBuilder API.

[nazar-pc]

I don't see why, we create RuntimeGenesisConfig struct explicitly and not using Default, why is Default a hard requirement there? Looks like it should be removed.

[michalkucharczyk]

It has been there for a while. IMO it can be relaxed.

[nazar-pc]

I'll look into it later then, thanks!