blog: Running Wasm Components From the Command Line (approved)

[tpmccallum]

This is an article demonstrating how to use the wasmtime run --invoke feature. It explains WAVE syntax and implements a component with an exported function that is invoked in the Wasmtime CLI.

Relates to Zulip chat at #wasmtime > Article announcing the new `--invoke` feature. @ 💬

Related GitHub URLs:

• Invoke wave enhancements wasmtime#10511
• wasmtime-cli: support run --invoke for components using wave wasmtime#10054
• https://github.com/bytecodealliance/wasmtime/tree/pch/invoke_wave

[vados-cosmonic]

Hey @tpmccallum thanks for writing this, this is an awesome intro to how to use wasmtime --invoke! I left a bunch of comments but feel free to take or leave any of them -- most are almost NIT level.

I know that trying to strike the balance between technical and approachable is absolutely devilish to pull off so feel free to ignore any overly technical points I made!

[vados-cosmonic]

Thanks for the hard work here -- I still have a few comments, but feel free to take/leave them!

[pchickey]

This is a great introductory blog post - thank you very much @tpmccallum for all your help getting the invoke PR across the finish line, and for writing this up!

[vados-cosmonic]

Thanks for making the changes @tpmccallum

On the interface/raw function export change, I think the --invoke invocation would change, so if you decide to take that change then running through it just once more is probably worth doing :)

[tpmccallum]

Thanks, @pchickey
Absolute pleasure! Congratulations on implementing such a great feature.

Thanks, @vados-cosmonic
I have updated the example to include the best practice of using the interface approach.
Further, I gave the article one final read-through and tested all the code and configuration (.wit, .rs, .toml, etc.) on the latest wasmtime commit. Works like a charm 💯

wasm_answer % wasmtime --version
wasmtime 33.0.0 (4d0a43fd0 2025-04-14)
wasm_answer % cargo component build --target wasm32-wasip2 --release                            
  Generating bindings for wasm_answer (src/bindings.rs)
    Finished `release` profile [optimized] target(s) in 0.01s
wasm_answer % wasmtime run --invoke 'get-answer()' target/wasm32-wasip2/release/wasm_answer.wasm
42

Please let me know if you need me to tweak the date in the .md or the file name's date (regarding the publish date). I am happy with it from my end and looking forward to this publishing when practicable for wasmtime release schedule etc.

Chat soon
Tim

[vados-cosmonic]

Thanks for really putting in the work here @tpmccallum -- this is going to be an amazing entry point for people into the ecosystem.

[pchickey]

Only marking this as "request changes" because I think we need to delay publishing until Wasmtime 33 is out. Also, I believe the policy is we need someone on the TSC to sign this off? one of @ricochet @ospencer @abrown @tschneidereit please

[pchickey]

We should wait to publish this until Wasmtime 33 is out - invoke didnt make it into the Wasmtime 32 release. I'd amend this to say it requires wasmtime 33 specifically, rather than the latest.

[tpmccallum]

Thank you @pchickey
I have updated the filename and the date in the frontmatter to align with the next expected release.
I have also updated the wasmtime section to specify v33.0.0 or newer.
Changes are in cb41248.
Ready for sign off cc: @ricochet @ospencer @abrown @tschneidereit.
Kind regards
Tim

[abrown]

@tpmccallum and I have talked about this but for anyone else wondering: this is on the agenda for the next TSC meeting (no hurry since we expect it to be published later in May).

[abrown]

This was discussed today in the TSC and we are all in favor of this being merged once Wasmtime v33 is out. Thanks again for working on this!

[ospencer]

This will be an excellent addition to the blog; thanks @tpmccallum for writing, and thank you to the others for their thorough reviews!