Re-add `*.witx` version of API

[abrown]

After some discussion with wit-bindgen maintainers, it is clear that that tool is not yet ready to use for implementing WASI APIs inside engines (e.g., Wasmtime). Since the existing Wasmtime infrastructure, wiggle, uses the WITX syntax, this change re-adds the WITX version of the wasi-nn API. This allows wiggle to continue to pull the WITX specification directly from this repository until it is replaced by wit-bindgen. All documentation has been removed from wasi-nn.witx since we expect the WIT version to be the official version (at some point, it would be nice to check in CI that the WITX and WIT versions expose an identical API but this API does not do that).

[gusye1234]

Gentle ping @abrown.

Hi, I'm curious, is there a way to check out the correctness of the syntax of the wasi-nn.witx? I'm trying to use witx-codegen to generate the official wasi-nn types and interfaces, but went into a mistake when witnext unable to parse the wasi-nn.witx file. To further test it, I also tried witx-bindgen, which seems to be used to generate the current rust interface. But still, unable to parse. I rolled back the master branch to test the old wasi_ephemeral_nn.witx and still got the same parse errors.

Errors' log for witx-bindgen:

↪ RUST_BACKTRACE=1 cargo run ~/Desktop/wasm/wasi-nn/phases/ephemeral/witx/wasi_ephemeral_nn.witx
    Finished dev [unoptimized + debuginfo] target(s) in 0.09s
     Running `/Users/gus/Desktop/wasm/wasi/target/debug/witx-bindgen /Users/gus/Desktop/wasm/wasi-nn/phases/ephemeral/witx/wasi_ephemeral_nn.witx`
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Parse(Error { inner: ErrorInner { text: Some(Text { line: 17, col: 8, snippet: "  (enum u16" }), file: Some("/Users/gus/Desktop/wasm/wasi-nn/phases/ephemeral/witx/wasi_ephemeral_nn.witx"), span: Span { offset: 944 }, kind: Custom("expected an identifier") } })', /Users/gus/Desktop/wasm/wasi/crates/witx-bindgen/src/lib.rs:9:38
stack backtrace:
   0: rust_begin_unwind
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:498:5
   1: core::panicking::panic_fmt
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:116:14
   2: core::result::unwrap_failed
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/result.rs:1690:5
   3: core::result::Result<T,E>::unwrap
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/result.rs:1018:23
   4: witx_bindgen::generate
             at ./src/lib.rs:9:15
   5: witx_bindgen::main
             at ./src/main.rs:9:18
   6: core::ops::function::FnOnce::call_once
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/ops/function.rs:227:5

Errors' log for witx-codegen:

↪ RURUST_BACKTRACE=1 target/debug/witx-codegen --output-type cpp ~/Desktop/wasm/wasi-nn/phases/ephemeral/witx/wasi_ephemeral_nn.witx
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Parse(Error { inner: ErrorInner { text: Some(Text { line: 12, col: 0, snippet: "(typename $buffer_size u32)" }), file: Some("/Users/gus/Desktop/wasm/wasi-nn/phases/ephemeral/witx/wasi_ephemeral_nn.witx"), span: Span { offset: 757 }, kind: Custom("extra tokens remaining after parse") } })', src/lib.rs:123:42
stack backtrace:
   0: rust_begin_unwind
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:498:5
   1: core::panicking::panic_fmt
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:116:14
   2: core::result::unwrap_failed
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/result.rs:1690:5
   3: core::result::Result<T,E>::unwrap
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/result.rs:1018:23
   4: witx_codegen::generate
             at ./src/lib.rs:123:20
   5: witx_codegen::main
             at ./src/main.rs:11:5
   6: core::ops::function::FnOnce::call_once
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/ops/function.rs:227:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[abrown]

@gusye1234, thanks for the heads up. Let me take a look tomorrow and see if I can't replicate what you found.

[abrown]

@gusye1234, I looked into this today and I'm not sure I can replicate what you see. One issue is that I'm not familiar with witnext and witx-codegen so I only tried witx-bindgen and that seemed to work. I also wonder if the switch that happened from master to main some time ago might be causing some issues. But, anyways, here is what I found:

1. I retrieved the latest version of the bytecodealliance/wasi repository and built witx-bindgen:

$ cd .../wasi/crates/witx-bindgen
$ git checkout main
$ git pull
$ git submodule update --init
$ cargo build
$ file ../../target/debug/witx-bindgen

2. Then I also made sure that I had latest version of the wasi-nn specification:

$ cd .../wasi-nn
$ git checkout main
$ git pull

3. I was then able to generate the Rust bindings for the specification without any parse errors:

$ ../../wasi/target/debug/witx-bindgen ../../wasi-nn/wasi-nn.witx

Not sure what is going on with your environment; does this step-by-step explanation highlight anything that might be different?

[gusye1234]

Thanks for your detailed reply! I cleaned out all my local repos and ran the witx-bindgen following your scripts, It works now. Probably there were some files outdated.