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Improve ICU4C-based Intl.DateTimeFormat implementation #1636

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9288a6e
Add Intl.DateTimeFormat implementation using ICU4C
robchu05 Mar 3, 2025
cf675f8
Add documentation and improve variable names
robchu05 Jun 2, 2025
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3 changes: 3 additions & 0 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -471,6 +471,9 @@ endif()

if (HERMES_ENABLE_INTL)
add_definitions(-DHERMES_ENABLE_INTL)
if (NOT (HERMES_IS_ANDROID OR APPLE))
add_definitions(-DHERMES_INTL_FORMAT_RANGE)
endif()
endif()

if (HERMES_ENABLE_UNICODE_REGEXP_PROPERTY_ESCAPES)
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11 changes: 11 additions & 0 deletions include/hermes/Platform/Intl/PlatformIntl.h
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Expand Up @@ -148,6 +148,17 @@ class DateTimeFormat : public vm::DecoratedObject::Decoration {

std::u16string format(double jsTimeValue) noexcept;
std::vector<Part> formatToParts(double jsTimeValue) noexcept;
#ifdef HERMES_INTL_FORMAT_RANGE
vm::CallResult<std::u16string> formatRange(
vm::Runtime &runtime,
double startUtcMs,
double endUtcMs) noexcept;

vm::CallResult<std::vector<Part>> formatRangeToParts(
vm::Runtime &runtime,
double startUtcMs,
double endUtcMs) noexcept;
#endif
};

class NumberFormat : public vm::DecoratedObject::Decoration {
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32 changes: 0 additions & 32 deletions include/hermes/Platform/Intl/PlatformIntlShared.h
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4 changes: 4 additions & 0 deletions include/hermes/VM/NativeFunctions.def
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Expand Up @@ -459,6 +459,10 @@ NATIVE_FUNCTION(intlDateTimeFormatFormat)
NATIVE_FUNCTION(intlDateTimeFormatSupportedLocalesOf)
NATIVE_FUNCTION(intlDateTimeFormatPrototypeFormatGetter)
NATIVE_FUNCTION(intlDateTimeFormatPrototypeFormatToParts)
#ifdef HERMES_INTL_FORMAT_RANGE
NATIVE_FUNCTION(intlDateTimeFormatPrototypeFormatRange)
NATIVE_FUNCTION(intlDateTimeFormatPrototypeFormatRangeToParts)
#endif
NATIVE_FUNCTION(intlDateTimeFormatPrototypeResolvedOptions)

NATIVE_FUNCTION(intlNumberFormatConstructor)
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4 changes: 4 additions & 0 deletions include/hermes/VM/PredefinedStrings.def
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Expand Up @@ -505,6 +505,10 @@ STR(Intl, "Intl")
STR(compare, "compare")
STR(format, "format")
STR(formatToParts, "formatToParts")
#ifdef HERMES_INTL_FORMAT_RANGE
STR(formatRange, "formatRange")
STR(formatRangeToParts, "formatRangeToParts")
#endif
STR(getCanonicalLocales, "getCanonicalLocales")
STR(resolvedOptions, "resolvedOptions")
STR(supportedLocalesOf, "supportedLocalesOf")
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3 changes: 2 additions & 1 deletion lib/Platform/Intl/BCP47Parser.cpp
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Expand Up @@ -46,7 +46,8 @@ bool isUnicodeRegionSubtag(const std::u16string &subtag) {
bool isUnicodeVariantSubtag(const std::u16string &subtag) {
// = (alphanum{5,8} | digit alphanum{3});
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@lavenzg lavenzg May 16, 2025

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Update the code comment accordingly.

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@robchu05 robchu05 May 30, 2025

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The existing code comment is correct. The previous code incorrectly missed the "digit" part in the "digit alphanum{3}" check.

return isCharType(subtag, 5, 8, &isASCIILetterOrDigit) ||
isCharType(subtag, 3, 3, &isASCIILetterOrDigit);
(subtag.size() == 4 && isASCIIDigit(subtag.front()) &&
isCharType(subtag.substr(1), 3, 3, &isASCIILetterOrDigit));
}
bool isUnicodeExtensionAttribute(const std::u16string &subtag) {
// = alphanum{3,8};
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3 changes: 2 additions & 1 deletion lib/Platform/Intl/CMakeLists.txt
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Expand Up @@ -24,13 +24,14 @@ if(HERMES_ENABLE_INTL)
else()
add_hermes_library(hermesPlatformIntl STATIC
PlatformIntlICU.cpp
PlatformIntlShared.cpp
impl_icu/Collator.cpp
impl_icu/DateTimeFormat.cpp
impl_icu/IntlUtils.cpp
impl_icu/LocaleConverter.cpp
impl_icu/LocaleBCP47Object.cpp
impl_icu/LocaleResolver.cpp
impl_icu/OptionHelpers.cpp
impl_icu/NumberingSystem.cpp
LINK_LIBS
hermesBCP47Parser
hermesPublic
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10 changes: 10 additions & 0 deletions lib/Platform/Intl/PlatformIntlApple.mm
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Expand Up @@ -1484,6 +1484,16 @@ uint8_t getCurrencyDigits(std::u16string_view code) {
// 30. Let dataLocaleData be localeData.[[<dataLocale>]].
// 31. Let matcher be ? GetOption(options, "formatMatcher", "string", «
// "basic", "best fit" », "best fit").
// NOTE: Only best fit format matcher is implemented through use of NSDateFormatter.
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@lavenzg lavenzg May 18, 2025

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This is unclear to me. "basic" format matcher isn't implemented? Or it's implemented without Platform API? If it's not implemented, where do we early return?

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@robchu05 robchu05 May 30, 2025

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The "basic" format matcher algorithm defined in the spec is not implemented. The Apple implementation uses the Apple Platform API to implement the "best fit" format matcher. And the "best fit" format matcher is used even when "basic" is specified.

"best fit" is defined in the spec to be a platform implementation that produces results at least as good as "basic", so it is fine to just always use the "best fit" format matcher.

// The formatMatcher option is read and checked for valid values.
auto formatMatcherRes = getOptionString(
runtime,
options,
u"formatMatcher",
{u"basic", u"best fit"},
u"best fit");
if (LLVM_UNLIKELY(formatMatcherRes == vm::ExecutionStatus::EXCEPTION))
return vm::ExecutionStatus::EXCEPTION;
// 32. Let dateStyle be ? GetOption(options, "dateStyle", "string", « "full",
// "long", "medium", "short" », undefined).
static constexpr std::u16string_view dateStyles[] = {
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