Create example(s) showing how to bind to Subxt from other languages

[jsdw]

Create an example showing how to bind to Subxt from several languages (eg, Python, Java) and use it to construct and/or submit transactions.

We should decide which language(s) are most important for the community and then create example bindings to those to accomplish a simple task (like submitting a transaction).

A single example should be applicable to several languages: we'd create bindings once and then show how they can be used in target langauges. We don't want to create bindings multiple times as this will be more of a maintenance headache.

Closed by #2037

[wassimans]

Hi @jsdw, could you please give more clarifications about when you say “we'd create bindings once,” are you picturing:

1. Hand-written, minimal FFI shims in each language?
2. A UniFFI UDL → autogenerated wrappers workflow?
3. Some other codegen/IDL tool?

[jsdw]

Basically, the approach would be to make a Rust crate which exposes some functionality via C, and then in whatever target language, use the C FFI bits to make use of those methods. Depending on the language, some of this may be automatable or not; I'm not sure offhand without trying (though in an example I'd keep the FFI bit fairly minimal so manually handling it on either side is probably fine, and good for an example to show the fundamentals of it that can be applied anywhere :))

[wassimans]

Thanks for the feedback. I asked because I'm working on a library that exposes Subxt to other languages via Mozilla's UniFFI, the idea is to create a Rust façade for the most used functionality of Subxt (like what a wallet typically needs) by exposing simple callable functions that themselves call Subxt with the typical boilerplate, the library publishes ready-to-use language-specific packages that can be imported using every language's package manager and then call the exposed functions directly.

As I understand it, you rather want a more bare bones example: as virtually every language can call C based ABIs, the idea is to expose some functionality in a Rust crate, build a static or dynamic lib, provide the matching C header then import and call in target language.

If this is the idea, I'll be happy to work on this issue.

[jsdw]

Thankyou!

I asked because I'm working on a library that exposes Subxt to other languages via Mozilla's UniFFI, the idea is to create a Rust façade for the most used functionality of Subxt (like what a wallet typically needs) by exposing simple callable functions that themselves call Subxt with the typical boilerplate, the library publishes ready-to-use language-specific packages that can be imported using every language's package manager and then call the exposed functions directly.

This sounds amazing; I'd love to know how you get on with this! If you do make good progress here I'd love to link to what you produce as a way to go about exposing Subxt in other languages :)

As I understand it, you rather want a more bare bones example: as virtually every language can call C based ABIs, the idea is to expose some functionality in a Rust crate, build a static or dynamic lib, provide the matching C header then import and call in target language.

This was my default approach, but if you have luck via the above then perhaps that ends up being a better way to go, or perhaps it's good to have both this UniFFI thing to make the general case easy, and an example or two showing the "raw" FFI approach for those that need lower level control!

[wassimans]

This sounds amazing; I'd love to know how you get on with this! If you do make good progress here I'd love to link to what you produce as a way to go about exposing Subxt in other languages :)

Sounds great thank you. I'll be happy to keep you informed as I progress.

This was my default approach, but if you have luck via the above then perhaps that ends up being a better way to go, or perhaps it's good to have both this UniFFI thing to make the general case easy, and an example or two showing the "raw" FFI approach for those that need lower level control!

I'll work on the "raw" example first, and then when I get my project on its feet (currently just a PoC) I'll get back to you for feedback and possible inclusion as a way to do FFI for Subxt.

[wassimans]

Hey @jsdw, just finished working on the example project. Before submitting a PR, let me give you the link to the repo, better for preliminary feedback:

https://github.com/wassimans/subxt-ffi

Thanks for your time.

[jsdw]

@wassimans I had a look and that looks awesome; thank you for your time on this! Exactly what I had in mind :)

I'd love a PR to add this into examples/ffi-example to sit alongside our parachain-example and wasm-example, but if you're short on time I can also make an issue to do that and get to it myself when I have the time!

[wassimans]

Thanks very much @jsdw for the positive feedback.

I've just submitted the PR.