Add a way to derive Clone for the generated Request and Response types

[ShaneMurphy2]

Currently tarpc::service creates request and response types that are not clone. This makes it difficult it difficult to test and mock. It would be nice if the service macro used an attribute macro to control adding derives for things like PartialEq, Clone, or Hash. Is there any reason not to do this? If there isn't, I can take a stab at it.

[tikue]

Thanks for the suggestion! I agree this could be supported.

It'd be nice to replace the derive_serde arg with something generic enough to support this new use case. Maybe something like this would be possible:

#[tarpc::service(derive = [tarpc::serde::Serialize, tarpc::serde::Deserialize, Clone, Hash])]
service World {
    async fn hello(message: String) -> String;
}

[ShaneMurphy2]

@tikue Got a first cut up on a branch: https://github.com/ShaneMurphy2/tarpc/tree/customizable-derives, let me know what you think so far.

Still need to see what breaks by changing the macro syntax, but the core use case works.

[tikue]

Looks nice! It'd be nice for derive_serde and derive to be mutually exclusive, so that people are encouraged to make the switch. In particular:

• derive_serde and derive at the same time should be an error
• derive should only derive Serialize/Deserialize when they are explicitly listed
• derive_serde is deprecated - output a warning when it is used, and suggest instead using either derive = [] to disable, or derive = [Serialize, Deserialize] to explicitly enable
• for backwards compatibility, absence of derive can derive Serialize/Deserialize by default.

[ShaneMurphy2]

Looks nice! It'd be nice for derive_serde and derive to be mutually exclusive, so that people are encouraged to make the switch. In particular:

• derive_serde and derive at the same time should be an error
• derive should only derive Serialize/Deserialize when they are explicitly listed
• derive_serde is deprecated - output a warning when it is used, and suggest instead using either derive = [] to disable, or derive = [Serialize, Deserialize] to explicitly enable
• for backwards compatibility, absence of derive can derive Serialize/Deserialize by default.

On it 👍

[ShaneMurphy2]

@tikue PR is up!