feat(wit): add map type support

[yordis]

Related Add a 'map<K,V>' type

[alexcrichton]

Thanks for this! Are you looking to get this merged ASAP? Or is this more of a proof-of-concept to support the development of the PR on the spec itself? If you're looking to get this merged sooner-rather-than-later, do you have plans to work on other parts of the stack such as wit-bindgen or Wasmtime?

[yordis]

@alexcrichton no rush at all in my end. I want to learn how to do the whole thing if possible if that is ok with you

[yordis]

Note for self: 0x63 why is that typed in so many places instead of having a enum somewhere?

[alexcrichton]

Ok looked over things, and thanks for this!

In terms of implementing this, adding a new type is a relatively major endeavor that takes awhile as there are a lot of integration points. Given that we'll want to make sure that this work is properly "gated" from external users to avoid, in theory, accidentally hitting unimplemented parts of the type system. The primary way this is done is via WasmFeatures in the wasmparser crate. What I'd recommend is adding a new cm_map feature similar to cm_fixed_size_lists. Effectively you'll want to add a bunch of tests/checks/etc in the same manner as fixed-size-lists, also an unstable feature at this time.

Additionally you'll want to add tests in tests/cli/component-model/*.wast for this new type as well. You should be able to find tests for fixed-size-lists around there and you can structure tests in a similar way.

Other than that though I think this would be reasonable to land. After landing here would come integration work into wasmtime/wit-bindgen/etc.

[alexcrichton]

Looking good, thanks! The remaining things I can think of are:

• This needs a new feature gate in wasmparser's validation to ensure that this isn't accidentally usable-by-default.
• This needs *.wast tests for the component-model side of things to ensure that the type works in the text format, validation, etc. There should also be tests ensuring that if the feature gate is disabled that usage of the type is an error (you can copy fixed-size-list tests for example)
• Tests are currently not passing in CI, so that'll need to be green

[alexcrichton]

@yordis it looks like the feature gating still isn't implemented?

[yordis]

@alexcrichton 🤦🏻 sorry ... I completely forgot focusing on making CI to pass again resolving the comments ... let me work on that

[yordis]

cargo fmt
Error writing files: failed to resolve mod bindings: /Users/yordisstudio/Developer/github.com/bytecodealliance/wasm-tools/playground/component/src/bindings.rs does not exist

@alexcrichton when I ran cargo fmt it seems that there is a missing file here, what is reason for that file to be missing from the code base? Or rather, at the very least be added to a .gitignore so I can keep a dummy file to make the formatter to work

[alexcrichton]

Sorry I'm not sure what you're referring to? If you run find . -name '*.rs' | xargs rustfmt --check --edition 2021 like CI does, does that fix things? (no CI is currently being run due to a merge conflict)

[yordis]

Sorry I'm not sure what you're referring to? If you run find . -name '*.rs' | xargs rustfmt --check --edition 2021 like CI does, does that fix things?

Yeah, just wondering why the cargo fmt by itself wouldn't work here, no biggy

[alexcrichton]

Thanks!

[alexcrichton]

I think the 37 here conflicts with compact_imports below now. I think it's reasonable to leave this adjacent to cm_gc, but feel free to renumber the below bits to ensure the biggest number is last

[yordis]

It scares me that my tests passed 😭 I do not like things no breaking with these type of changes.

Could this use a enum thou?

[yordis]

I rather keep it based on the flag value than grouping things ... I think that caused the issue to begin with