Import attributes

[zth]

https://github.com/tc39/proposal-import-attributes

Closes: #6500

cc @cometkim

[cometkim]

I prefer a syntax that explicitly provides the "with" key rather than having the special keys (that is the whole point of the spec over the import assertion) .

This is common even in regular js syntax.

// import attrs can be specified with others e.g. import assertion
import module from "module-id" asserts { type: "json" } with { type: "json" }

// import attrs in dynamic imports
import("module-id", { with: { ... } })

// import attra in workers
new Worker("id", { with: { ... } })

// Notice that the "type" in the top-level and the "type" in the import attributes (with) have different semantic
new Worker("id", { type: "module", with: { type: "something-special" } })

[zth]

Can you write an example of how you'd want it to look?

[cometkim]

@module({from: "./myJson.json", with: { type_: "json"}})

[zth]

Right. Curious, can more things appear in that with list than type?

[zth]

Ok @cometkim look again.

[cometkim]

Right. Curious, can more things appear in that with list than type?

Yes, import attributes are freely extensible and their behavior is determined by the host (mostly bundlers).

[zth]

@cometkim is the input/output fine now?

[cometkim]

yep, it will be better if we have other random cases than type_ in the test

[zth]

@cristianoc @mununki you recently did dynamic imports. Interested in your take on whether what I've done here is reasonable/correct or if there's a better way.

[cometkim]

Suggested change

	@module({from: "./myJson.json", with: {type_: "json"}})
	external myJson: Js.Json.t = "default"
	@module({from: "./myJson.json", with: {type_: "json"}})
	external myJson: Js.Json.t = "default"
	@module({from: "./myModule", with: {foo: "foo", "bar-baz": "only-string-allowed"}})
	external moreAttributes: unit = "default"
	@module({with: {type_: "css"}})
	external styles: Styles.t = "./myModule.css"

[zth]

Yeah it doesn't handle invalid identifiers yet, but that would be easy to handle by just outputting quotes around the keys. That should be fine, right?

You'd have to escape the identifiers BTW, it needs to be a record in the AST.

[zth]

@cometkim I updated the code to handle this case, and added an example to the test output. Let me know what you think.

[zth]

@cometkim does this look good from your end in terms of functionality provided?

[cometkim]

@zth It looks great for default export! Does it support non-default access too? It would be also common by CSS modules or something

[zth]

@cometkim it should, yes. Should add a test for that too.

If you think it all looks good, we can go ahead and get this into 11.1.

[cometkim]

gogo 🚀

[cristianoc]

go ahead as long as it's obvious that this does not affect existing code