FFI bindings don't get rebuild when spade interface changes

[icewind1991]

When taking the code from the spade quickstart[1], building it at least once, and renaming the output parameter from out to out2 results in an error as the FFI bindings still reference the old name:

../ffi/ffi.cpp:26:21: error: ‘class Vmain’ has no member named ‘out’; did you mean ‘out2’?

Making any change to the rust side of the code will cause the bindings to be rebuild and the name changes to be picked up.

[1]: From the behavior and my (limited) understanding of how this works, I expect the other backends will also have this problem.

[ethanuppal]

The issue is that your struct binding on the Rust side, e.g.

#[spade(src = "src/main.spade", name = "main")]
pub struct Main;

was not updated. If you use LSP hover on Main, you will see that, unless Rust has recompiled the file, the member is still listed as out. This is because there's no way for Rust to know that an update in an external file can affect a proc macro. If you, for instance, edit whitespace anywhere in the file, it will work.

I'm not entirely sure how to solve this; I can mention this papercut in the docs, though.

[icewind1991]

I think you can get the desired behavior in a macro by generating a include_str! call. But there is some complication there as they use different base paths (relative to source file vs relative to crate root)

[ethanuppal]

Can probably get crate root with CARGO_MANIFEST_DIR but sadly don't think that can be concat!ed.