parse import assertions

[xtuc]

Refs #11917

What kind of change does this PR introduce?

Parsing import assertions syntax

Did you add tests for your changes?
Yes, one. Most of the tests are in https://github.com/xtuc/acorn-import-assertions/tree/main/test/fixtures

Does this PR introduce a breaking change?
no

What needs to be documented once your changes are merged?
probably not now, import assertions doesn't emit runtime code yet

[webpack-bot]

For maintainers only:

• This needs to be documented (issue in webpack/webpack.js.org will be filed when merged)
• This needs to be backported to webpack 4 (issue will be created when merged)

[alexander-akait]

Tests are broken 😞

[xtuc]

@alexander-akait yes noticed that too. I was wondering if those failures are related to my change? I can't see the detail of the failures but they are mismatching stats? I'll try to run them locally again

[xtuc]

@alexander-akait tests are passing now, coverage is failing and https://dev.azure.com/webpack/webpack/_build/results?buildId=12330&view=logs&j=1d505e51-909d-5717-0d5b-43f6a0bd49f6&t=6309f675-4460-5c1b-70bc-fd472dead250 is flaky. Could you please restart for me?

[alexander-akait]

@vankop thanks)

[xtuc]

right, sorry I forgot about that trick! thanks

[xtuc]

@sokra could you please take a look at the PR? the idea is that we allow parsing and stripping out import assertions for now.
Next steps would be to emit runtime code to check the type of dynamically loaded resources.

[sokra]

Next steps would be to emit runtime code to check the type of dynamically loaded resources.

JSON is not loaded dynamically but embedded into the JS file. As it's parsed during build it's already verified that it's really JSON and not JS or something else.

I think what we can do it to set the module type for imports with assert { type: "json" } to JSON so they go through the JSON parser. This could be done by allowing an assert condition in module.rules and adding a default rule to set type: "json" for assert: { type: "json" } (module.defaultRules: [ ..., { assert: { type: "json" }, type: "json" }] in lib/config/defaults.js).

For a assert condition we need to pass the assert value from HarmonyImportDependencyParserPlugin -> ModuleDependency.assert (getResourceIdentifier need to have assert too) -> NormalModuleFactory (add assert to ruleSetCompiler, and pass the value when executing it, get it from dependencies[0].assert).

[xtuc]

JSON is not loaded dynamically but embedded into the JS file. As it's parsed during build it's already verified that it's really JSON and not JS or something else.

I was thinking of loading dynamically remote resources. Like: import("https://a.com/great-json.php"), the runtime should ensure that the response is indeed JSON. But we can do that later.

Thanks for your pointers, i'll do that change.

[xtuc]

@sokra I believe I have implemented what you suggested. One test doesn't pass yet and we probably want to show a code frame when the assertion aren't met, that's still WIP. Could you please do an early review?

[xtuc]

@sokra could you please review the change so far? I believe it matches what you suggested.

[sokra]

Thanks

[xtuc]

Great, thanks for your help!

[redonkulus]

@sokra is #13814 related to this merge?

[alexander-akait]

@redonkulus yep

[sodatea]

Should assert be mentioned in https://webpack.js.org/configuration/module/#rule ?
I've seen it used in css-loader examples but can't find it in the webpack documentation.

[alexander-akait]

@sodatea Yes, feel free to open an issue