URL: Fix URLSearchParams to further avoid decoding URIError #1174
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Ref JakeChampion#1173. Ref JakeChampion#4. Co-authored-by: David Chan <david@troi.org>
Krinkle
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Thanks for this @Krinkle - I've triggered CI to run the tests, they should be running at https://github.com/Financial-Times/polyfill-library/actions/runs/1989744310 |
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| // This can't simply use decodeURIComponent (part of ECMAScript) as that's limited to | ||
| // decoding to valid UTF-8 only. It throws URIError for literals that look like percent | ||
| // encoding (e.g. `x=%`, `x=%a`, and `x=a%2sf`) and for non-UTF8 binary data that was | ||
| // percent encoded and cannot be turned back into binary within a JavaScript string. | ||
| // | ||
| // The spec deals with this as follows: | ||
| // * Read input as UTF-8 encoded bytes. This needs low-level access or a modern | ||
| // Web API, like TextDecoder. Old browsers don't have that, and it'd a large | ||
| // dependency to add to this polyfill. | ||
| // * For each percentage sign followed by two hex, blindly decode the byte in binary | ||
| // form. This would require TextEncoder to not corrupt multi-byte chars. | ||
| // * Replace any bytes that would be invalid under UTF-8 with U+FFFD. | ||
| // | ||
| // Instead we: | ||
| // * Use the fact that UTF-8 is designed to make validation easy in binary. | ||
| // You don't have to decode first. There are only a handful of valid prefixes and | ||
| // ranges, per RFC 3629. <https://datatracker.ietf.org/doc/html/rfc3629#section-3> | ||
| // * Safely create multi-byte chars with decodeURIComponent, by only passing it | ||
| // valid and full characters (e.g. "%F0" separately from "%F0%9F%92%A9" throws). | ||
| // Anything else is kept as literal or replaced with U+FFFD, as per the URL spec. |
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This is excellent, thank you for this detailed comment
JakeChampion
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Mar 16, 2022
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Ref #1173.
Ref #4.
Co-authored-by: David Chan david@troi.org