Disallow unknown import attributes

Category: JavaScript
Type: No developer-visible change
Status: Enabled by default (Chrome 119)
Intent stage: None

Summary

Throw an error when using unknown keys in import attributes (formerly known as import assertions), such as "import 'x' assert { unknown: 'val' }`, rather than ignoring them. The only accepted attribute remains "type".

Standards & signals

Specification: https://tc39.es/import-attributes
Firefox: No signal
Safari: No signal
Web developers: No signals

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