[Webkit-unassigned] [Bug 229313] New: Intl.DateTimeFormat incorrectly parses patterns with 'h' literal

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=229313

            Bug ID: 229313
           Summary: Intl.DateTimeFormat incorrectly parses patterns with
                    'h' literal
           Product: WebKit
           Version: Safari Technology Preview
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: govett at adobe.com

WebKit parses the date/time pattern returned from ICU to do two things: 

1. Determine the `resolvedOptions` - https://github.com/WebKit/WebKit/blob/796333669f054bfaf1e50247d659dfa8834182a7/Source/JavaScriptCore/runtime/IntlDateTimeFormat.cpp#L318
2. To replace the hour part in the pattern when the `hourCycle` option is specified - https://github.com/WebKit/WebKit/blob/796333669f054bfaf1e50247d659dfa8834182a7/Source/JavaScriptCore/runtime/IntlDateTimeFormat.cpp#L486

However, these methods do not take into account that there may be literal parts in quotes which may contain otherwise meaningful symbols which should be ignored. For example, the hour pattern in the `fr` locale has the following pattern: `HH 'h'` https://github.com/unicode-org/cldr/blob/018b55eff7ceb389c7e3fc44e2f657eae3b10b38/common/main/fr.xml#L2962. When WebKit parses this pattern, it interprets the `h` as a symbol but it should be ignored instead.

This manifests in two ways:

1. The resolved `hour12` and `hourCycle` options for the French locale (and any other locale with patterns like this) are incorrect. For example, `new Intl.DateTimeFormat("fr", {hour: "numeric", hour12: false}).resolvedOptions().hour12` results in `true` rather than false, even though the date is formatted in 24 hour time: `new Intl.DateTimeFormat("fr", {hour: "numeric", hour12: false}).format(new Date(2021, 2, 3, 23))` results in `23 h`.

2. When specifying the `hourCycle` option, literals in the pattern are replaced resulting in incorrect formatting. For example, `new Intl.DateTimeFormat("fr", {hour: "numeric", hourCycle: 'h24'}).format(new Date(2021, 2, 3, 23))` results in `23 k` rather than `23 h`, and `new Intl.DateTimeFormat("fr", {hour: "numeric", hourCycle: 'h23'}).format(new Date(2021, 2, 3, 23))` results in `23 H`.

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