imp: make it easier to use custom verifiers for Tendermint clients

[Farhad-Shabani]

Relevant context: #1166 (comment)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.72%. Comparing base (68513d8) to head (8fe4460).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1168      +/-   ##
==========================================
- Coverage   63.79%   63.72%   -0.08%     
==========================================
  Files         219      218       -1     
  Lines       21389    21394       +5     
==========================================
- Hits        13646    13633      -13     
- Misses       7743     7761      +18     

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[rnbguy]

Left some comments.

[rnbguy]

I am a bit confused about how I would reuse this interface for a custom verifier. After I implement Verifier trait for my custom logic, how do I pass it here instead of ProdVerifier::default()?

[Farhad-Shabani]

See if this works. b8244a5

[rnbguy]

Am I correct to conclude that someone has to create a wrapper struct:

struct CustomClientState(ClientState);

and delegate all calls except this one? If I am correct, can we add a generic to the current ClientState?

struct ClientState<V: Verifier + Default> { ... }

type DefaultClientState = ClientState<ProdVerifier>;
type SovClientState = ClientState<SovVerifier>;

I am just confirming my understanding. If you already plan for this in future PRs, go ahead with this current merge.

[Farhad-Shabani]

Am I correct to conclude that someone has to create a wrapper struct

That's right

Can we add a generic to the current ClientState

Our plan was to do this, but adding a generic introduces complications that eventually lead to refactoring some of the APIs as well. Aside from that, we didn't want to introduce complexity to normal users.
We can consider the generic or even writing macros in the future if there be a serious need.

[rnbguy]

LGTM ✨ Thanks !