replace strict typed casting with deserialization

[miraclx]

Fixes #61, alternative to #73, depends on a small patch to SDK – near/near-sdk-rs#939.

[itegulov]

So, this has fewer problems than our current approach, but it still depends on Rust ABI not changing between the point when you compiled cargo-near and when you are invoking it (e.g. you used rustc 1.61 to compile cargo-near, but now you are using rustc 1.64 to compile your smart contract).

From what I understand Rust ABI is not stable, so I would not be comfortable with depending on it not changing, unless someone has more insight on this topic. CC @austinabell

[itegulov]

But thinking about this a bit more, couldn't we avoid Rust ABI entirely and load this with libloading::Symbol<extern "C" fn() -> String> instead? We would have to change the way SDK exposes the symbol obviously, but that should not be a big deal.

[miraclx]

@itegulov, yeah I came to the same conclusion, but to be safe, we can replace String entirely with *const c_char

[itegulov]

Hmm, weird. Have you tried it? I am getting an empty file instead of ABI.

[miraclx]

Yeah, it works. Although, for posterity, the empty file issue was fixed in #75.

[miraclx]

This patch requires a version of near-sdk that uses near-abi v0.2.0. So we'll have to merge #55 before this.

CI fails for this reason. https://github.com/near/cargo-near/actions/runs/3281321184/jobs/5403176360#step:4:1081

[itegulov]

This looks good to me, but lets wait for the SDK change to come in first

[miraclx]

@itegulov, this is ready. What do you think? Can you test it out?

[itegulov]

@miraclx hmm weird it is not working for me. Tried our classic adder example and got this:

[miraclx]

Have you tried cleaning your target folder? Maybe cargo is returning an artifact from previous builds? In the meantime, I'll spin up a Linux machine and see if I can reproduce this.

[itegulov]

@miraclx yep, sorry, must have had some leftover artifacts indeed. Works fine now!

[itegulov]

LGTM. Don't forget to update the git rev to the master commit though once the SDK PR is merged.

[miraclx]

You got it, chief!