`Symbol.toStringTag` is missing on `File`, `Blob` and `FormData`

[octet-stream]

Hi. I have discovered that Symbol.toStringTag is missing on File, Blob and FormData which causes compatibility issues for my library, which implements FormData and few other interfaces for Node. Some people still using it and they have this kind of issue, when they need to use it with fetch API. You can find more information here: octet-stream/form-data#57

This symbol is present in every implementation I've tested: Chrome v118.0.5993.117, Safari v17.1, Firefox v116.0.3, Deno v1.37.2, Node v21.1.0 (which inherits its implementation from undici), and Bun v1.0.8. I think this symbol should be present in types as well.

For more context: I also use this property for Symbol.hasInstance checks in my FormData, File and Blob implementations to verify if given value is an object that implements compatible API for these interfaces.

[saschanaz]

Per the spec it should exist for every Web IDL interface: https://webidl.spec.whatwg.org/#ref-for-dfn-class-string

PR welcome.

[jdufresne]

Per the spec it should exist for every Web IDL interface: https://webidl.spec.whatwg.org/#ref-for-dfn-class-string

@saschanaz Could you provide some guidance on how to approach this issue with the provided information?

Without knowing better, my first instinct would be to add this property to inputfiles/overridingTypes.jsonc, but your statement leads me to believe you're expecting something more.

Thanks.