[feature request] Type substitution from CLI for codegen command

[deuszx]

As in the title - it would be nice to be able to substitute types when generating API via codegen.

0.26.0 release changed, among many things, what AccountId32 type is: previously it was subxt::ext::sp_core::crypto::AccountId32 and now it's subxt::utils::AccountId32. Even when re-exporting sp_core and sp_runtime these types will remain the same - subxt::utils::AccountId32. It would be nice either opt-out from the default substitutions (from the CLI) or override it.

The UX could be:

subxt codegen --url ${NODE_URL} \
	--derive Debug --derive Clone ... \
	--substitute type::from::A:type::into::APrime \
    --substitute type::from::B:type::into::BPrime \
    | rustfmt ... > node_api.rs

EDIT: Alternatively, we could introduce an argument --substrate-impl (to follow the feature from base subxt) that would use sp_core::* types automatically.

[jsdw]

Interesting; yeah it def makes sense to expose the substitute type stuff in codegen! Ideally we'd expose the full power of the substitute API also and allow for generics to be substituted too. The --derive-for-type flag accepts something like path::to::TypeName=SomeDerive, so I'd be inclined to go for--substitute-type path::to::TypeName<MaybeGenerics>=MySubstituteType<MaybeGenerics>