implement deserialize_reader

[Arshia001]

Add support for deserialization of data within an std::io::Read.

This is a breaking change. The old deserialize API is still available for consumers of the crate, but code that uses the BorshDeserialize derive macro needs to be re-compiled, as the macro definition has changed.

[Arshia001]

I have no idea why this PR was created in the upstream repository, must have clicked the wrong button. Wanted to create it in our own. I'll take this as a sign and leave it here for review though.

The serializer already supports std::io::Write, so we wondered why std::io::Read wasn't supported in the deserializer. If there's a good reason, feel free to reject this change please :)

[frol]

This is a breaking change. The old deserialize API is still available for consumers of the crate, but code that uses the BorshDeserialize derive macro needs to be re-compiled, as the macro definition has changed.

This does not sound like a breaking change to me if neither public interfaces nor serialization format is changed.

Overall, it seems to be a nice feature to have. Please, add tests. Unless anyone else raises their concern against merging it, I am happy to approve and merge this one.

[Arshia001]

Actually, you're right. It'd be a breaking change if you had pre-compiled code, but rust already compiles everything from scratch each time, so it's not. I'll get to work on the tests.

[Arshia001]

@frol that's all the tests I can think of. If there's anything else, please let me know.

[frol]

@Arshia001 Please, address the clippy warnings

[Arshia001]

@frol should be fixed now.

[frol]

@Arshia001 Thank you for the contribution!

[Arshia001]

@frol you're welcome.

Also, this is a breaking change after all; any manually implemented deserializers will need be reimplemented over the new trait. I don't know how likely users are to have manually implemented deserializers, but this change will definitely break them.

[frol]

@Arshia001 Ah, indeed, I missed that bit. I will tick the minor version and indicate this breakage in the release notes.

May I ask you to add a record about this feature and the breaking change to the CHANGELOG.md?

[Arshia001]

Sorry it took a while; I was sick these past few days.