TC39 has consensus for trying to deprecate and remove the `assert` keyword in favor of the new `with` keyword in import attribute syntax. That is, `import m from 'foo' assert { type: 'json' }` will now throw a SyntaxError, and developers must change to `import m from 'foo' with { type: 'json' }`. https://github.com/tc39/proposal-import-attributes/issues/135
The import assertions proposal (now called "import attributes") [1] in TC39 shipped in M91 with the `import mod from 'foo' assert { type: 'json' }` syntax. The original semantics was that additional information following the `assert` keyword cannot cause the module to be reinterpreted or change the semantics of the module in any way, i.e., a pure assertion. Following an HTML integration issue with CSP [2] that required changing Accept headers depending on the requested module type, TC39 reached consensus that the "pure assertion" semantics are to be relaxed to allow reinterpretation, and that the `assert` keyword be changed to `with` to reflect the new semantics. [1] https://github.com/tc39/proposal-import-attributes/ [2] https://github.com/whatwg/html/issues/7233