Issue linking cache interface in `rust-consumer`

[kate-goldenring]

When following this awesome write-up I ran into issues linking the Wasm library to the rust-consumer module with wasmlink.

To get wasmlink I cloned the wit-bindgen repo and followed the wasmlink README to build it. Specifically, I ran, cargo build -p wasmlink-cli, which resulted in output built to wit-bindgen/target/debug/wasmlink. I modified the first line of the rust-consumer Makefile to target this binary for wasmlink.

Then, I built (with make build) and tried to link the WASI library and run the rust-consumer with make link run. make link fails with:

[2021-12-27T17:44:56Z ERROR] failed to parse interface file `../cache.wit`
    
    Caused by:
        invalid character in identifier '_'
             --> ../cache.wit:4:5
              |
            4 |     runtime_error,
              |     ^
make: *** [Makefile:9: link] Error 1

The interface file was successfully used to build the Wasm library (rust_wasi_impl.wasm); however, wasmlink seems unable to use it. Is there a different way I should be building and running wasmlink?

[radu-matei]

First, make sure to use the same revision for the wit-bindgen crates and Wasmlink — specifically, https://github.com/bytecodealliance/wit-bindgen/tree/32e63116d469d8046727fae3c1333a7d35d0c5d3.

Install wasmlink-cli from that commit, and let me know if that works.
(the article and this repo are pinned to a revision before some breaking changes to WIT, which happened in bytecodealliance/wit-bindgen#119)

[radu-matei]

See fermyon/wasi-experimental-toolkit#3 for some updates related to this change.

[kate-goldenring]

I installed wasmlink-cli from the above commit and am pointing to it from the rust-consumer Makefile; however, while make link with wasmlink succeeds, make run is failing with the following error that the --enable-module-linking subcommand DNE:

kagold@akri-dev:~/radu-demo/rust-consumer$ make link run
/home/kagold/radu-demo/wit-bindgen/target/debug/wasmlink ../rust-consumer/target/wasm32-wasi/release/rust-consumer.wasm \
        --interface cache=../cache.wit \
        --profile wasmtime \
        --module cache=../rust-wasi-impl/target/wasm32-wasi/release/rust_wasi_impl.wasm \
        --output linked.wasm
wasmtime --enable-module-linking --enable-multi-memory --mapdir=/cache::. linked.wasm
error: Found argument '--enable-module-linking' which wasn't expected, or isn't valid in this context

USAGE:
    wasmtime <SUBCOMMAND>

For more information try --help
make: *** [Makefile:16: run] Error 1

I am using verion 0.33 of wasmtime as recommended in the example -- I installed it from here.

[radu-matei]

Ah, you are correct.
I just pushed a new commit with the correct CLI usage.

[kate-goldenring]

Ah, you are correct. I just pushed a new commit with the correct CLI usage.

That did the trick! 🥳 😃 I also added this print statement to rust-consumer/src/main.rs in order to make the make link run output match that of the writeup. Thanks for all the help!

[radu-matei]

Yaay, glad it worked, and sorry for the version mismatch.