LGTM2

On Monday, September 29, 2025 at 11:25:35 AM UTC-7 [email protected] 
wrote:

> LGTM1; thanks for doing this so carefully.
>
> On Friday, September 26, 2025 at 12:05:02 PM UTC-7 Chromestatus wrote:
>
>> *Contact emails*
>> [email protected]
>>
>> *Specification*
>> https://url.spec.whatwg.org/#idna 
>>
>> *Summary*
>> IDNA is the mechanism for non-ASCII characters in domain names, encoding 
>> a URL like http://네이버.한국/ as http://xn--950bt9s8xi.xn--3e0b707e/ (a 
>> redirect to naver.com). The processing is defined by 
>> https://www.unicode.org/reports/tr46/#Processing and is invoked by 
>> https://url.spec.whatwg.org/#idna. The URL spec sets the CheckJoiners 
>> flag, which enables the ContextJ rules in IDNA2008: 
>> https://www.rfc-editor.org/rfc/rfc5892.html#appendix-A.1 
>> https://www.rfc-editor.org/rfc/rfc5892.html#appendix-A.2 This disallows 
>> ZWNJ (U+200C ZERO WIDTH NON-JOINER) and ZWJ (U+200D ZERO WIDTH JOINER) in 
>> most places in URLs. The implementation is to simply pass the 
>> UIDNA_CHECK_CONTEXTJ option to ICU, where this rule is implemented: 
>> https://source.chromium.org/chromium/chromium/src/+/main:third_party/icu/source/common/uts46.cpp;l=1137-1204;drc=8a1988938d4298fbe8fb499b1a59fe4b04a21b15
>>  
>> This would fix over 200 subtests in WPT relating to IDNA, which already 
>> pass in Firefox and Safari: 
>> https://chromium-review.googlesource.com/c/chromium/src/+/6990929 
>> https://wpt.fyi/results/url/IdnaTestV2.window.html All of the IdnaTestV2 
>> cases that would regress from shipping ICU 77 (
>> https://chromestatus.com/feature/5143313833000960) would also be fixed 
>> again by this change. 
>>
>> *Blink component*
>> Blink>Network 
>> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ENetwork%22>
>>
>> *Web Feature ID*
>> url <https://webstatus.dev/features/url> 
>>
>> *Search tags*
>> idna <http:///features#tags:idna>
>>
>> *TAG review*
>> None 
>>
>> *TAG review status*
>> Not applicable
>>
>> *Risks*
>>
>>
>> *Interoperability and Compatibility*
>> Interoperability is improved by bringing URL parsing closer to Firefox 
>> and Safari. The web compat risk is most likely very low because the URLs 
>> that will be rejected don't work at all in Firefox or Safari. On the other 
>> hand, any breakage would be very severe for the same reason. To make this 
>> change safely I would suggest a gradual Finch rollout. 
>>
>> *Gecko*: Shipped/Shipping Shipped for a long time, exact version not 
>> found
>>
>> *WebKit*: Shipped/Shipping Shipped for a long time, exact version not 
>> found
>>
>> *Web developers*: No signals
>>
>> *Other signals*:
>>
>> *WebView application risks*
>>
>> Does this intent deprecate or change behavior of existing APIs, such that 
>> it has potentially high risk for Android WebView-based applications? 
>> None 
>>
>>
>> *Debuggability*
>> None 
>>
>> *Will this feature be supported on all six Blink platforms (Windows, Mac, 
>> Linux, ChromeOS, Android, and Android WebView)?*
>> Yes
>>
>> *Is this feature fully tested by web-platform-tests 
>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?*
>> Yeshttps://wpt.fyi/results/url/IdnaTestV2.window.html
>>
>> *Flag name on about://flags*
>> None 
>>
>> *Finch feature name*
>> UseIDNAContextJRules 
>>
>> *Rollout plan*
>> (RARE) Experiment users ramp up over time
>>
>> *Requires code in //chrome?*
>> False
>>
>> *Tracking bug*
>> https://crbug.com/40765949
>>
>> *Measurement*
>> Cannot be measured with use counters because the URL parser is used in 
>> many places in Chrome, and not all of them have access to an 
>> ExecutionContext or similar. UMA could be used and give a proportion of URL 
>> parses affected metric, but given how many URLs are parsed and how rare 
>> even valid IDNA URLs seem to be, the number is probably vanishingly small 
>> and not informative of risk.
>>
>> *Estimated milestones*
>> Shipping on desktop 143 
>> Shipping on Android 143 
>> Shipping on WebView 143 
>>
>> *Anticipated spec changes*
>>
>> Open questions about a feature may be a source of future web compat or 
>> interop issues. Please list open issues (e.g. links to known github issues 
>> in the project for the feature specification) whose resolution may 
>> introduce web compat/interop risk (e.g., changing to naming or structure of 
>> the API in a non-backward-compatible way). 
>> None
>>
>> *Link to entry on the Chrome Platform Status*
>> https://chromestatus.com/feature/6295810820145152?gate=5173132017139712
>>
>> This intent message was generated by Chrome Platform Status 
>> <https://chromestatus.com>. 
>>
>

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