Adds registry metadata

[silesmo]

Adds support for registry metadata as discussed: bytecodealliance/registry#116

[calvinrp]

Couple suggestions / questions:

• add the command so that it can be used from wasm-tools CLI, e.g. wasm-tools registry-metadata print (not sure about the naming, maybe package show and package set?);
• there is a metadata command already, should we consider putting it under that command? probably not but asking the question
• currently need to call with args for the input path, e.g. registry-metadata-cli -p some.wasm print; can we also do registry-metadata-cli print some.wasm?
• add an option to provide a JSON file input or STDIN? (probably minifying the JSON before putting into the custom section)
• maybe add test / example cases with links being exercised?

[alexcrichton]

Thanks for this! I'd second all of what @calvinrp said as well. For organization it'd be best to put the new executable under src/bin/wasm-tools/*.rs, ideally in the metadata.rs file by augmenting that existing comment. This ideally would prevent duplicating the loops to read/write from the existing wasm-metadata crate as well. (possibly merging the crates together too)

[silesmo]

Thanks for this! I'd second all of what @calvinrp said as well. For organization it'd be best to put the new executable under src/bin/wasm-tools/*.rs, ideally in the metadata.rs file by augmenting that existing comment. This ideally would prevent duplicating the loops to read/write from the existing wasm-metadata crate as well. (possibly merging the crates together too)

Yes I agree with this. I was hesitant to do this initially since I wasn't sure we even wanted this in the wasm-tools repo. But if we are happy with that when I will make those changes!

[silesmo]

Couple suggestions / questions:

* add the command so that it can be used from `wasm-tools` CLI, e.g. `wasm-tools registry-metadata print` (not sure about the naming, maybe `package show` and `package set`?);

* there is a `metadata` command already, should we consider putting it under that command? probably not but asking the question

* currently need to call with args for the input path, e.g. `registry-metadata-cli -p some.wasm print`; can we also do `registry-metadata-cli print some.wasm`?

* add an option to provide a JSON file input or STDIN? (probably minifying the JSON before putting into the custom section)

* maybe add test / example cases with `links` being exercised?

Thanks for the suggestions. I will go ahead and make the suggested changes.

[alexcrichton]

Oh to be clear I'm not sure if this is the best place for this to live either. I can provide feedback on how to integrate this once it's decided to integrate here, but I'd leave that up to other folks to make the judgement call of whether this belongs here.

[silesmo]

I will bring it up in the wasm-registry sig meeting later today and we will see after that.

[esoterra]

We discussed this topic yesterday and reached a consensus around putting it in the wasm-tools repo so that it can be read from and written to using wasm-encoder/decoder more easily.

One way to think about including this is that it's a not-completely-standard custom section and as long as we call that out, I think it's fine to have support for it in wasm-tools. This isn't that different from encoding/decoding DWARF into custom sections for debugging tools. If needed, we can even hide it behind a feature flag to make it only visible/usable by people who want it.

[calvinrp]

Looks good to me. Thank you!

[silesmo]

This should be ready to be reviewed now.
@alexcrichton or @Kylebrown9 if you have the time to take a look

[alexcrichton]

Seems reasonable to me! One minor question about what to do in the appending case, but otherwise seems reasonable to me to add