Import assertions are skipped when transpiled from TS to JS

[andreubotella]

Describe the bug

Import assertions affect whether a module is valid in the module graph, depending on the JS runtime, and so should not be stripped when transpiling.

Input code

import data from "./test.json" assert { type: "json" };

console.log(data);

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "tsx": false
    },
    "target": "es2022",
    "loose": false,
    "minify": {
      "compress": false,
      "mangle": false
    }
  },
  "module": {
    "type": "es6"
  },
  "minify": false,
  "isModule": true
}

Playground link

https://play.swc.rs/?version=1.2.122&code=H4sIAAAAAAAAA8vMLcgvKlFISSxJVEgrys9VUNLTL0ktLtHLKs7PU1JILC5OBUpXK5RUFqRaKShBRGutubiS8%2FOK83NS9XLy0zVAujWtAVSAl05LAAAA&config=H4sIAAAAAAAAA0WNSwrDMAxE76J1FsWLLnKHHsK4SnDxD40CDcZ3rx1cspNmnp4qfeBorVSsgGVMOJPaL62kZ2E48UVpIUWPNhvArS9WdtaOMMzDmF6HnMETWCj65LdzyFyORRi4K5v28Cdbd8X8PkZQr3%2BX80ntdsw7j9cEVQ5uPx%2Bqcl%2B4AAAA

Expected behavior

import data from "./test.json" assert { type: "json" };
console.log(data);

Actual behavior

import data from "./test.json";
console.log(data);

Version

1.2.122

Additional context

No response

[kdy1]

Closing as duplicate of #2802

[wycats]

@kdy1 It seems like the solution in #2802 involved a new flag that only applies to the ECMAScript parser.

Also, maybe I'm doing something wrong, but when I attempted to add the flag to the example in the playground in the JSON editor (after updating the version to the latest available version and switching to ECMAScript), it still seems to strip it out.

[kdy1]

@wycats TypeScript supports it unconditionally.

swc/crates/swc_ecma_parser/src/lib.rs

Lines 167 to 174 in 7407f21

	pub fn import_assertions(self) -> bool {
	match self {
	Syntax::Es(EsConfig {
	import_assertions, ..
	}) => import_assertions,
	Syntax::Typescript(_) => true,
	}
	}

[kdy1]

Also, I tested and import is stripped out because imported identifier isn't used.
See https://play.swc.rs/?version=1.2.189&code=H4sIAAAAAAAAA8vMLcgvKlFQ19NPy8xJ1csqzs9TV0gsLk4FClYrlFQWpFopKIFElRRqAUUfytcsAAAA&config=H4sIAAAAAAAAA02PsW7DMAxE%2F4VzhjZDB28FOiRDPkJQz4YaSRRIprBh%2BN9LOQbSTRTvHu9W%2BtFIw0otiEL6S5dqYaaBbGnQKKkZncjUv8aQFZsPQSaYS6Dnt%2FO7rzOzggaTB05UUk3j0lmRSxOoHlZfhTpl%2FCNJqDqylK7OmEJcvhBZgrE8cS7CbJAa8gW5QV4wzD6mAs%2Bbu%2F8OtGtpLPapXsYSVz0gTin8%2Fein173YHv6DtlfaA5r0dgifZVB%2Fd89e2XFE2%2FYHgsdGZDYBAAA%3D

This is related to preserving imports not used as value ( I don't remember the name of the option for preserving such imports)

[wycats]

Great! Consider this solved.

I'm not sure why it was causing me trouble in my real app (it wasn't this problem), but I can dig in if I reproduce it again.

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.