Should named JSON module import be a parsing stage error?

[JLHwung]

Currently Babel parser throws syntax error for the following cases:

import { foo } from "./foo" asserts { type: "json" };

which conforms to this test262 test.

But the spec only states that JSON module should provide only a single default export, so a SyntaxError should be thrown no later than the module resolution stage. However unlike random modules, a parser can recognize JSON module imports thanks to the import assertion syntax. So should a JavaScript parser throw such errors?

Either way an end user will not observe any differences, but it helps us define the scope.

Context: babel/babel#14816

[ljharb]

It’s a host-dependent behavior, and the assertion is not supposed to be required outside a browser. It definitely should error, but probably not at the parsing stage.

[Boshen]

Given this proposal is stage 4, these are the remaining test262 case we are unable to flag as syntax errors:

• https://github.com/tc39/test262/blob/e48df0b96457b67b2d81fab16cabb230152a6c57/test/language/import/json-named-bindings.js
• https://github.com/tc39/test262/blob/e48df0b96457b67b2d81fab16cabb230152a6c57/test/language/import/json-invalid.js

Should phase in the test cases be changed to resolution?

https://github.com/tc39/test262/blob/e48df0b96457b67b2d81fab16cabb230152a6c57/INTERPRETING.md#negative:

phase - the stage of the test interpretation process that the error is expected to be produced; valid phases are:
parse: occurs while parsing the source text, or while checking it for early errors.
resolution: occurs during module resolution.
runtime: occurs during evaluation.