Issue #1701 - Implement Intl.PluralRules API

7 files changed, 832 insertions, 67 deletions

diff --git a/js/public/Class.h b/js/public/Class.h
index 9cb377892..094e4a7ed 100644
--- a/js/public/Class.h
+++ b/js/public/Class.h
@@ -778,7 +778,7 @@ struct JSClass {
 // application.
 #define JSCLASS_GLOBAL_APPLICATION_SLOTS 5
 #define JSCLASS_GLOBAL_SLOT_COUNT                                             \
-    (JSCLASS_GLOBAL_APPLICATION_SLOTS + JSProto_LIMIT * 2 + 45)
+    (JSCLASS_GLOBAL_APPLICATION_SLOTS + JSProto_LIMIT * 2 + 46)
 #define JSCLASS_GLOBAL_FLAGS_WITH_SLOTS(n)                                    \
     (JSCLASS_IS_GLOBAL | JSCLASS_HAS_RESERVED_SLOTS(JSCLASS_GLOBAL_SLOT_COUNT + (n)))
 #define JSCLASS_GLOBAL_FLAGS                                                  \
diff --git a/js/src/builtin/Intl.cpp b/js/src/builtin/Intl.cpp
index d231d7bec..622e773e0 100644
--- a/js/src/builtin/Intl.cpp
+++ b/js/src/builtin/Intl.cpp
@@ -10,6 +10,7 @@
 
 #include "builtin/Intl.h"
 
+#include "mozilla/Casting.h"
 #include "mozilla/PodOperations.h"
 #include "mozilla/Range.h"
 #include "mozilla/ScopeExit.h"
@@ -22,6 +23,7 @@
 #include "jsobj.h"
 
 #include "builtin/IntlTimeZoneData.h"
+#include "unicode/plurrule.h"
 #include "unicode/ucal.h"
 #include "unicode/ucol.h"
 #include "unicode/udat.h"
@@ -29,6 +31,7 @@
 #include "unicode/uenum.h"
 #include "unicode/unum.h"
 #include "unicode/unumsys.h"
+#include "unicode/upluralrules.h"
 #include "unicode/ustring.h"
 #include "vm/DateTime.h"
 #include "vm/GlobalObject.h"
@@ -43,6 +46,7 @@
 
 using namespace js;
 
+using mozilla::AssertedCast;
 using mozilla::IsFinite;
 using mozilla::IsNegativeZero;
 using mozilla::MakeScopeExit;
@@ -963,6 +967,89 @@ js::intl_numberingSystem(JSContext* cx, unsigned argc, Value* vp)
 }
 
 /**
+ *
+ * This creates new UNumberFormat with calculated digit formatting
+ * properties for PluralRules.
+ *
+ * This is similar to NewUNumberFormat but doesn't allow for currency or
+ * percent types.
+ *
+ */
+static UNumberFormat*
+NewUNumberFormatForPluralRules(JSContext* cx, HandleObject pluralRules)
+{
+    RootedObject internals(cx, GetInternals(cx, pluralRules));
+    if (!internals)
+       return nullptr;
+
+    RootedValue value(cx);
+
+    if (!GetProperty(cx, internals, internals, cx->names().locale, &value))
+        return nullptr;
+    JSAutoByteString locale(cx, value.toString());
+    if (!locale)
+        return nullptr;
+
+    uint32_t uMinimumIntegerDigits = 1;
+    uint32_t uMinimumFractionDigits = 0;
+    uint32_t uMaximumFractionDigits = 3;
+    int32_t uMinimumSignificantDigits = -1;
+    int32_t uMaximumSignificantDigits = -1;
+
+    RootedId id(cx, NameToId(cx->names().minimumSignificantDigits));
+    bool hasP;
+    if (!HasProperty(cx, internals, id, &hasP))
+        return nullptr;
+    if (hasP) {
+        if (!GetProperty(cx, internals, internals, cx->names().minimumSignificantDigits,
+                         &value))
+            return nullptr;
+        uMinimumSignificantDigits = value.toInt32();
+
+        if (!GetProperty(cx, internals, internals, cx->names().maximumSignificantDigits,
+                         &value))
+            return nullptr;
+        uMaximumSignificantDigits = value.toInt32();
+    } else {
+        if (!GetProperty(cx, internals, internals, cx->names().minimumIntegerDigits,
+                         &value))
+            return nullptr;
+        uMinimumIntegerDigits = AssertedCast<uint32_t>(value.toInt32());
+
+        if (!GetProperty(cx, internals, internals, cx->names().minimumFractionDigits,
+                         &value))
+            return nullptr;
+        uMinimumFractionDigits = AssertedCast<uint32_t>(value.toInt32());
+
+        if (!GetProperty(cx, internals, internals, cx->names().maximumFractionDigits,
+                         &value))
+            return nullptr;
+        uMaximumFractionDigits = AssertedCast<uint32_t>(value.toInt32());
+    }
+
+    UErrorCode status = U_ZERO_ERROR;
+    UNumberFormat* nf = unum_open(UNUM_DECIMAL, nullptr, 0, icuLocale(locale.ptr()), nullptr, &status);
+    if (U_FAILURE(status)) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INTERNAL_INTL_ERROR);
+        return nullptr;
+    }
+    ScopedICUObject<UNumberFormat, unum_close> toClose(nf);
+
+    if (uMinimumSignificantDigits != -1) {
+        unum_setAttribute(nf, UNUM_SIGNIFICANT_DIGITS_USED, true);
+        unum_setAttribute(nf, UNUM_MIN_SIGNIFICANT_DIGITS, uMinimumSignificantDigits);
+        unum_setAttribute(nf, UNUM_MAX_SIGNIFICANT_DIGITS, uMaximumSignificantDigits);
+    } else {
+        unum_setAttribute(nf, UNUM_MIN_INTEGER_DIGITS, uMinimumIntegerDigits);
+        unum_setAttribute(nf, UNUM_MIN_FRACTION_DIGITS, uMinimumFractionDigits);
+        unum_setAttribute(nf, UNUM_MAX_FRACTION_DIGITS, uMaximumFractionDigits);
+    }
+
+    return toClose.forget();
+}
+
+
+/**
  * Returns a new UNumberFormat with the locale and number formatting options
  * of the given NumberFormat.
  */
@@ -1044,35 +1131,25 @@ NewUNumberFormat(JSContext* cx, HandleObject numberFormat)
     if (hasP) {
         if (!GetProperty(cx, internals, internals, cx->names().minimumSignificantDigits,
                          &value))
-        {
             return nullptr;
-        }
-        uMinimumSignificantDigits = int32_t(value.toNumber());
+        uMinimumSignificantDigits = value.toInt32();
         if (!GetProperty(cx, internals, internals, cx->names().maximumSignificantDigits,
                          &value))
-        {
             return nullptr;
-        }
-        uMaximumSignificantDigits = int32_t(value.toNumber());
+        uMaximumSignificantDigits = value.toInt32();
     } else {
         if (!GetProperty(cx, internals, internals, cx->names().minimumIntegerDigits,
                          &value))
-        {
             return nullptr;
-        }
-        uMinimumIntegerDigits = int32_t(value.toNumber());
+        uMinimumIntegerDigits = AssertedCast<uint32_t>(value.toInt32());
         if (!GetProperty(cx, internals, internals, cx->names().minimumFractionDigits,
                          &value))
-        {
             return nullptr;
-        }
-        uMinimumFractionDigits = int32_t(value.toNumber());
+        uMinimumFractionDigits = AssertedCast<uint32_t>(value.toInt32());
         if (!GetProperty(cx, internals, internals, cx->names().maximumFractionDigits,
                          &value))
-        {
             return nullptr;
-        }
-        uMaximumFractionDigits = int32_t(value.toNumber());
+        uMaximumFractionDigits = AssertedCast<uint32_t>(value.toInt32());
     }
 
     if (!GetProperty(cx, internals, internals, cx->names().useGrouping, &value))
@@ -2323,6 +2400,381 @@ js::intl_FormatDateTime(JSContext* cx, unsigned argc, Value* vp)
     return true;
 }
 
+/**************** PluralRules *****************/
+
+static void pluralRules_finalize(FreeOp* fop, JSObject* obj);
+
+static const uint32_t UPLURAL_RULES_SLOT = 0;
+static const uint32_t PLURAL_RULES_SLOTS_COUNT = 1;
+
+static const ClassOps PluralRulesClassOps = {
+    nullptr, /* addProperty */
+    nullptr, /* delProperty */
+    nullptr, /* getProperty */
+    nullptr, /* setProperty */
+    nullptr, /* enumerate */
+    nullptr, /* resolve */
+    nullptr, /* mayResolve */
+    pluralRules_finalize
+};
+
+static const Class PluralRulesClass = {
+    js_Object_str,
+    JSCLASS_HAS_RESERVED_SLOTS(PLURAL_RULES_SLOTS_COUNT) |
+    JSCLASS_FOREGROUND_FINALIZE,
+    &PluralRulesClassOps
+};
+
+#if JS_HAS_TOSOURCE
+static bool
+pluralRules_toSource(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    args.rval().setString(cx->names().PluralRules);
+    return true;
+}
+#endif
+
+static const JSFunctionSpec pluralRules_static_methods[] = {
+    JS_SELF_HOSTED_FN("supportedLocalesOf", "Intl_PluralRules_supportedLocalesOf", 1, 0),
+    JS_FS_END
+};
+
+static const JSFunctionSpec pluralRules_methods[] = {
+    JS_SELF_HOSTED_FN("resolvedOptions", "Intl_PluralRules_resolvedOptions", 0, 0),
+    JS_SELF_HOSTED_FN("select", "Intl_PluralRules_select", 1, 0),
+#if JS_HAS_TOSOURCE
+    JS_FN(js_toSource_str, pluralRules_toSource, 0, 0),
+#endif
+    JS_FS_END
+};
+
+/**
+ * PluralRules constructor.
+ * Spec: ECMAScript 402 API, PluralRules, 1.1
+ */
+static bool
+PluralRules(JSContext* cx, const CallArgs& args, bool construct)
+{
+    RootedObject obj(cx);
+
+    if (!construct) {
+        JSObject* intl = GlobalObject::getOrCreateIntlObject(cx, cx->global());
+        if (!intl)
+            return false;
+        RootedValue self(cx, args.thisv());
+        if (!self.isUndefined() && (!self.isObject() || self.toObject() != *intl)) {
+            obj = ToObject(cx, self);
+            if (!obj)
+                return false;
+
+            bool extensible;
+            if (!IsExtensible(cx, obj, &extensible))
+                return false;
+            if (!extensible)
+                return Throw(cx, obj, JSMSG_OBJECT_NOT_EXTENSIBLE);
+        } else {
+            construct = true;
+        }
+    }
+    if (construct) {
+        RootedObject proto(cx, GlobalObject::getOrCreatePluralRulesPrototype(cx, cx->global()));
+        if (!proto)
+            return false;
+        obj = NewObjectWithGivenProto(cx, &PluralRulesClass, proto);
+        if (!obj)
+            return false;
+
+        obj->as<NativeObject>().setReservedSlot(UPLURAL_RULES_SLOT, PrivateValue(nullptr));
+    }
+
+    RootedValue locales(cx, args.get(0));
+    RootedValue options(cx, args.get(1));
+
+    if (!IntlInitialize(cx, obj, cx->names().InitializePluralRules, locales, options))
+        return false;
+
+    args.rval().setObject(*obj);
+    return true;
+}
+
+static bool
+PluralRules(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return PluralRules(cx, args, args.isConstructing());
+}
+
+bool
+js::intl_PluralRules(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    MOZ_ASSERT(args.length() == 2);
+    return PluralRules(cx, args, true);
+}
+
+static void
+pluralRules_finalize(FreeOp* fop, JSObject* obj)
+{
+    MOZ_ASSERT(fop->onMainThread());
+
+    // This is-undefined check shouldn't be necessary, but for internal
+    // brokenness in object allocation code.  For the moment, hack around it by
+    // explicitly guarding against the possibility of the reserved slot not
+    // containing a private.  See bug 949220.
+    const Value& slot = obj->as<NativeObject>().getReservedSlot(UPLURAL_RULES_SLOT);
+    if (!slot.isUndefined()) {
+        if (UPluralRules* pr = static_cast<UPluralRules*>(slot.toPrivate()))
+            uplrules_close(pr);
+    }
+}
+
+static JSObject*
+CreatePluralRulesPrototype(JSContext* cx, HandleObject Intl, Handle<GlobalObject*> global)
+{
+    RootedFunction ctor(cx);
+    ctor = global->createConstructor(cx, &PluralRules, cx->names().PluralRules, 0);
+    if (!ctor)
+        return nullptr;
+
+    RootedNativeObject proto(cx, GlobalObject::createBlankPrototype(cx, global, &PluralRulesClass));
+    if (!proto)
+        return nullptr;
+    proto->setReservedSlot(UPLURAL_RULES_SLOT, PrivateValue(nullptr));
+
+    if (!LinkConstructorAndPrototype(cx, ctor, proto))
+        return nullptr;
+
+    if (!JS_DefineFunctions(cx, ctor, pluralRules_static_methods))
+        return nullptr;
+
+    if (!JS_DefineFunctions(cx, proto, pluralRules_methods))
+        return nullptr;
+
+    RootedValue options(cx);
+    if (!CreateDefaultOptions(cx, &options))
+        return nullptr;
+
+    if (!IntlInitialize(cx, proto, cx->names().InitializePluralRules, UndefinedHandleValue,
+                        options))
+    {
+        return nullptr;
+    }
+
+    RootedValue ctorValue(cx, ObjectValue(*ctor));
+    if (!DefineProperty(cx, Intl, cx->names().PluralRules, ctorValue, nullptr, nullptr, 0))
+        return nullptr;
+
+    return proto;
+}
+
+bool
+js::intl_PluralRules_availableLocales(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    MOZ_ASSERT(args.length() == 0);
+
+    RootedValue result(cx);
+    // We're going to use ULocale availableLocales as per ICU recommendation:
+    // https://ssl.icu-project.org/trac/ticket/12756
+    if (!intl_availableLocales(cx, uloc_countAvailable, uloc_getAvailable, &result))
+        return false;
+    args.rval().set(result);
+    return true;
+}
+
+bool
+js::intl_SelectPluralRule(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    RootedObject pluralRules(cx, &args[0].toObject());
+
+    UNumberFormat* nf = NewUNumberFormatForPluralRules(cx, pluralRules);
+    if (!nf)
+        return false;
+
+    ScopedICUObject<UNumberFormat, unum_close> closeNumberFormat(nf);
+
+    RootedObject internals(cx, GetInternals(cx, pluralRules));
+    if (!internals)
+        return false;
+
+    RootedValue value(cx);
+
+    if (!GetProperty(cx, internals, internals, cx->names().locale, &value))
+        return false;
+    JSAutoByteString locale(cx, value.toString());
+    if (!locale)
+        return false;
+
+    if (!GetProperty(cx, internals, internals, cx->names().type, &value))
+        return false;
+    JSAutoByteString type(cx, value.toString());
+    if (!type)
+        return false;
+
+    double x = args[1].toNumber();
+
+    // We need a NumberFormat in order to format the number
+    // using the number formatting options (minimum/maximum*Digits)
+    // before we push the result to PluralRules
+    //
+    // This should be fixed in ICU 59 and we'll be able to switch to that
+    // API: http://bugs.icu-project.org/trac/ticket/12763
+    //
+    RootedValue fmtNumValue(cx);
+    if (!intl_FormatNumber(cx, nf, x, &fmtNumValue))
+        return false;
+    RootedString fmtNumValueString(cx, fmtNumValue.toString());
+    AutoStableStringChars stableChars(cx);
+    if (!stableChars.initTwoByte(cx, fmtNumValueString))
+        return false;
+
+    const UChar* uFmtNumValue = Char16ToUChar(stableChars.twoByteRange().begin().get());
+
+    UErrorCode status = U_ZERO_ERROR;
+
+    UFormattable* fmt = unum_parseToUFormattable(nf, nullptr, uFmtNumValue,
+                                                 stableChars.twoByteRange().length(), 0, &status);
+    if (U_FAILURE(status)) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INTERNAL_INTL_ERROR);
+        return false;
+    }
+
+    ScopedICUObject<UFormattable, ufmt_close> closeUFormattable(fmt);
+
+    double y = ufmt_getDouble(fmt, &status);
+    if (U_FAILURE(status)) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INTERNAL_INTL_ERROR);
+        return false;
+    }
+
+    UPluralType category;
+
+    if (equal(type, "cardinal")) {
+        category = UPLURAL_TYPE_CARDINAL;
+    } else {
+        MOZ_ASSERT(equal(type, "ordinal"));
+        category = UPLURAL_TYPE_ORDINAL;
+    }
+
+    UPluralRules* pr = uplrules_openForType(icuLocale(locale.ptr()), category, &status);
+    if (U_FAILURE(status)) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INTERNAL_INTL_ERROR);
+        return false;
+    }
+
+    ScopedICUObject<UPluralRules, uplrules_close> closePluralRules(pr);
+
+    Vector<char16_t, INITIAL_CHAR_BUFFER_SIZE> chars(cx);
+    if (!chars.resize(INITIAL_CHAR_BUFFER_SIZE))
+        return false;
+
+    int size = uplrules_select(pr, y, Char16ToUChar(chars.begin()), INITIAL_CHAR_BUFFER_SIZE, &status);
+    if (status == U_BUFFER_OVERFLOW_ERROR) {
+        if (!chars.resize(size))
+            return false;
+        status = U_ZERO_ERROR;
+        uplrules_select(pr, y, Char16ToUChar(chars.begin()), size, &status);
+    }
+    if (U_FAILURE(status)) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INTERNAL_INTL_ERROR);
+        return false;
+    }
+
+    JSString* str = NewStringCopyN<CanGC>(cx, chars.begin(), size);
+    if (!str)
+        return false;
+
+    args.rval().setString(str);
+    return true;
+}
+
+bool
+js::intl_GetPluralCategories(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    MOZ_ASSERT(args.length() == 2);
+
+    JSAutoByteString locale(cx, args[0].toString());
+    if (!locale)
+        return false;
+
+    JSAutoByteString type(cx, args[1].toString());
+    if (!type)
+        return false;
+
+    UErrorCode status = U_ZERO_ERROR;
+
+    UPluralType category;
+
+    if (equal(type, "cardinal")) {
+        category = UPLURAL_TYPE_CARDINAL;
+    } else {
+        MOZ_ASSERT(equal(type, "ordinal"));
+        category = UPLURAL_TYPE_ORDINAL;
+    }
+
+    UPluralRules* pr = uplrules_openForType(
+        icuLocale(locale.ptr()),
+        category,
+        &status
+    );
+    if (U_FAILURE(status)) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INTERNAL_INTL_ERROR);
+        return false;
+    }
+
+    ScopedICUObject<UPluralRules, uplrules_close> closePluralRules(pr);
+
+    // We should get a C API for that in ICU 59 and switch to it
+    // https://ssl.icu-project.org/trac/ticket/12772
+    //
+    icu::StringEnumeration* kwenum =
+        reinterpret_cast<icu::PluralRules*>(pr)->getKeywords(status);
+    UEnumeration* ue = uenum_openFromStringEnumeration(kwenum, &status);
+
+    if (U_FAILURE(status)) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INTERNAL_INTL_ERROR);
+        return false;
+    }
+
+    ScopedICUObject<UEnumeration, uenum_close> closeEnum(ue);
+
+    RootedObject res(cx, NewDenseEmptyArray(cx));
+    if (!res)
+        return false;
+
+    RootedValue element(cx);
+    uint32_t i = 0;
+    int32_t catSize;
+    const char* cat;
+
+    do {
+        cat = uenum_next(ue, &catSize, &status);
+        if (U_FAILURE(status)) {
+            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INTERNAL_INTL_ERROR);
+            return false;
+        }
+
+        if (!cat)
+            break;
+
+        JSString* str = NewStringCopyN<CanGC>(cx, cat, catSize);
+        if (!str)
+            return false;
+
+        element.setString(str);
+        if (!DefineElement(cx, res, i, element))
+            return false;
+        i++;
+    } while (true);
+
+    args.rval().setObject(*res);
+    return true;
+}
+
 bool
 js::intl_GetCalendarInfo(JSContext* cx, unsigned argc, Value* vp)
 {
@@ -2761,6 +3213,9 @@ GlobalObject::initIntlObject(JSContext* cx, Handle<GlobalObject*> global)
     RootedObject numberFormatProto(cx, CreateNumberFormatPrototype(cx, intl, global));
     if (!numberFormatProto)
         return false;
+    RootedObject pluralRulesProto(cx, CreatePluralRulesPrototype(cx, intl, global));
+    if (!pluralRulesProto)
+        return false;
 
     // The |Intl| object is fully set up now, so define the global property.
     RootedValue intlValue(cx, ObjectValue(*intl));
@@ -2782,6 +3237,7 @@ GlobalObject::initIntlObject(JSContext* cx, Handle<GlobalObject*> global)
     global->setReservedSlot(COLLATOR_PROTO, ObjectValue(*collatorProto));
     global->setReservedSlot(DATE_TIME_FORMAT_PROTO, ObjectValue(*dateTimeFormatProto));
     global->setReservedSlot(NUMBER_FORMAT_PROTO, ObjectValue(*numberFormatProto));
+    global->setReservedSlot(PLURAL_RULES_PROTO, ObjectValue(*pluralRulesProto));
 
     // Also cache |Intl| to implement spec language that conditions behavior
     // based on values being equal to "the standard built-in |Intl| object".
diff --git a/js/src/builtin/Intl.h b/js/src/builtin/Intl.h
index 5384d9be1..fd1fc5da6 100644
--- a/js/src/builtin/Intl.h
+++ b/js/src/builtin/Intl.h
@@ -358,6 +358,54 @@ intl_patternForSkeleton(JSContext* cx, unsigned argc, Value* vp);
 extern MOZ_MUST_USE bool
 intl_FormatDateTime(JSContext* cx, unsigned argc, Value* vp);
 
+/******************** PluralRules ********************/
+
+/**
+ * Returns a new PluralRules instance.
+ * Self-hosted code cannot cache this constructor (as it does for others in
+ * Utilities.js) because it is initialized after self-hosted code is compiled.
+ *
+ * Usage: pluralRules = intl_PluralRules(locales, options)
+ */
+extern MOZ_MUST_USE bool
+intl_PluralRules(JSContext* cx, unsigned argc, Value* vp);
+
+/**
+ * Returns an object indicating the supported locales for plural rules
+ * by having a true-valued property for each such locale with the
+ * canonicalized language tag as the property name. The object has no
+ * prototype.
+ *
+ * Usage: availableLocales = intl_PluralRules_availableLocales()
+ */
+extern MOZ_MUST_USE bool
+intl_PluralRules_availableLocales(JSContext* cx, unsigned argc, Value* vp);
+
+/**
+ * Returns a plural rule for the number x according to the effective
+ * locale and the formatting options of the given PluralRules.
+ *
+ * A plural rule is a grammatical category that expresses count distinctions
+ * (such as "one", "two", "few" etc.).
+ *
+ * Usage: rule = intl_SelectPluralRule(pluralRules, x)
+ */
+extern MOZ_MUST_USE bool
+intl_SelectPluralRule(JSContext* cx, unsigned argc, Value* vp);
+
+/**
+ * Returns an array of plural rules categories for a given
+ * locale and type.
+ *
+ * Usage: categories = intl_GetPluralCategories(locale, type)
+ *
+ * Example:
+ *
+ * intl_getPluralCategories('pl', 'cardinal'); // ['one', 'few', 'many', 'other']
+ */
+extern MOZ_MUST_USE bool
+intl_GetPluralCategories(JSContext* cx, unsigned argc, Value* vp);
+
 /**
  * Returns a plain object with calendar information for a single valid locale
  * (callers must perform this validation).  The object will have these
diff --git a/js/src/builtin/Intl.js b/js/src/builtin/Intl.js
index 6391c3e70..281b0f424 100644
--- a/js/src/builtin/Intl.js
+++ b/js/src/builtin/Intl.js
@@ -21,6 +21,9 @@
          intl_availableCalendars: false,
          intl_patternForSkeleton: false,
          intl_FormatDateTime: false,
+         intl_SelectPluralRule: false,
+         intl_GetPluralCategories: false,
+         intl_GetCalendarInfo: false,
 */
 
 /*
@@ -857,6 +860,7 @@ function BestAvailableLocaleIgnoringDefault(availableLocales, locale) {
     return BestAvailableLocaleHelper(availableLocales, locale, false);
 }
 
+var noRelevantExtensionKeys = [];
 
 /**
  * Compares a BCP 47 language priority list against the set of locales in
@@ -1270,7 +1274,9 @@ function initializeIntlObject(obj) {
 function setLazyData(internals, type, lazyData)
 {
     assert(internals.type === "partial", "can't set lazy data for anything but a newborn");
-    assert(type === "Collator" || type === "DateTimeFormat" || type == "NumberFormat", "bad type");
+    assert(type === "Collator" || type === "DateTimeFormat" ||
+           type == "NumberFormat" || type === "PluralRules",
+           "bad type");
     assert(IsObject(lazyData), "non-object lazy data");
 
     // Set in reverse order so that the .type change is a barrier.
@@ -1320,7 +1326,9 @@ function isInitializedIntlObject(obj) {
     if (IsObject(internals)) {
         assert(callFunction(std_Object_hasOwnProperty, internals, "type"), "missing type");
         var type = internals.type;
-        assert(type === "partial" || type === "Collator" || type === "DateTimeFormat" || type === "NumberFormat", "unexpected type");
+        assert(type === "partial" || type === "Collator" ||
+               type === "DateTimeFormat" || type === "NumberFormat" || type === "PluralRules",
+               "unexpected type");
         assert(callFunction(std_Object_hasOwnProperty, internals, "lazyData"), "missing lazyData");
         assert(callFunction(std_Object_hasOwnProperty, internals, "internalProps"), "missing internalProps");
     } else {
@@ -1377,6 +1385,8 @@ function getInternals(obj)
         internalProps = resolveCollatorInternals(lazyData)
     else if (type === "DateTimeFormat")
         internalProps = resolveDateTimeFormatInternals(lazyData)
+    else if (type === "PluralRules")
+        internalProps = resolvePluralRulesInternals(lazyData)
     else
         internalProps = resolveNumberFormatInternals(lazyData);
     setInternalProperties(internals, internalProps);
@@ -1776,45 +1786,39 @@ function resolveNumberFormatInternals(lazyNumberFormatData) {
     // Step 6.
     var opt = lazyNumberFormatData.opt;
 
-    // Compute effective locale.
-    // Step 9.
     var NumberFormat = numberFormatInternalProperties;
 
-    // Step 10.
+    // Step 9.
     var localeData = NumberFormat.localeData;
 
-    // Step 11.
+    // Step 10.
     var r = ResolveLocale(callFunction(NumberFormat.availableLocales, NumberFormat),
                           lazyNumberFormatData.requestedLocales,
                           lazyNumberFormatData.opt,
                           NumberFormat.relevantExtensionKeys,
                           localeData);
 
-    // Steps 12-13.  (Step 14 is not relevant to our implementation.)
+    // Steps 11-12.  (Step 13 is not relevant to our implementation.)
     internalProps.locale = r.locale;
     internalProps.numberingSystem = r.nu;
 
     // Compute formatting options.
-    // Step 16.
+    // Step 15.
     var s = lazyNumberFormatData.style;
     internalProps.style = s;
 
-    // Steps 20, 22.
+    // Steps 19, 21.
     if (s === "currency") {
         internalProps.currency = lazyNumberFormatData.currency;
         internalProps.currencyDisplay = lazyNumberFormatData.currencyDisplay;
     }
 
-    // Step 24.
     internalProps.minimumIntegerDigits = lazyNumberFormatData.minimumIntegerDigits;
 
-    // Steps 27.
     internalProps.minimumFractionDigits = lazyNumberFormatData.minimumFractionDigits;
 
-    // Step 30.
     internalProps.maximumFractionDigits = lazyNumberFormatData.maximumFractionDigits;
 
-    // Step 33.
     if ("minimumSignificantDigits" in lazyNumberFormatData) {
         // Note: Intl.NumberFormat.prototype.resolvedOptions() exposes the
         // actual presence (versus undefined-ness) of these properties.
@@ -1823,10 +1827,10 @@ function resolveNumberFormatInternals(lazyNumberFormatData) {
         internalProps.maximumSignificantDigits = lazyNumberFormatData.maximumSignificantDigits;
     }
 
-    // Step 35.
+    // Step 27.
     internalProps.useGrouping = lazyNumberFormatData.useGrouping;
 
-    // Step 42.
+    // Step 34.
     internalProps.boundFormat = undefined;
 
     // The caller is responsible for associating |internalProps| with the right
@@ -1854,6 +1858,41 @@ function getNumberFormatInternals(obj, methodName) {
     return internalProps;
 }
 
+/**
+ * Applies digit options used for number formatting onto the intl object.
+ *
+ * Spec: ECMAScript Internationalization API Specification, 11.1.1.
+ */
+function SetNumberFormatDigitOptions(lazyData, options, mnfdDefault) {
+    // We skip Step 1 because we set the properties on a lazyData object.
+
+    // Step 2-3.
+    assert(IsObject(options), "SetNumberFormatDigitOptions");
+    assert(typeof mnfdDefault === "number", "SetNumberFormatDigitOptions");
+
+    // Steps 4-6.
+    const mnid = GetNumberOption(options, "minimumIntegerDigits", 1, 21, 1);
+    const mnfd = GetNumberOption(options, "minimumFractionDigits", 0, 20, mnfdDefault);
+    const mxfd = GetNumberOption(options, "maximumFractionDigits", mnfd, 20);
+
+    // Steps 7-8.
+    let mnsd = options.minimumSignificantDigits;
+    let mxsd = options.maximumSignificantDigits;
+
+    // Steps 9-11.
+    lazyData.minimumIntegerDigits = mnid;
+    lazyData.minimumFractionDigits = mnfd;
+    lazyData.maximumFractionDigits = mxfd;
+
+    // Step 12.
+    if (mnsd !== undefined || mxsd !== undefined) {
+        mnsd = GetNumberOption(options, "minimumSignificantDigits", 1, 21, 1);
+        mxsd = GetNumberOption(options, "maximumSignificantDigits", mnsd, 21, 21);
+        lazyData.minimumSignificantDigits = mnsd;
+        lazyData.maximumSignificantDigits = mxsd;
+    }
+}
+
 
 /**
  * Initializes an object as a NumberFormat.
@@ -1903,7 +1942,7 @@ function InitializeNumberFormat(numberFormat, locales, options) {
     //   }
     //
     // Note that lazy data is only installed as a final step of initialization,
-    // so every Collator lazy data object has *all* these properties, never a
+    // so every NumberFormat lazy data object has *all* these properties, never a
     // subset of them.
     var lazyNumberFormatData = std_Object_create(null);
 
@@ -1933,11 +1972,11 @@ function InitializeNumberFormat(numberFormat, locales, options) {
     opt.localeMatcher = matcher;
 
     // Compute formatting options.
-    // Step 15.
+    // Step 14.
     var s = GetOption(options, "style", "string", ["decimal", "percent", "currency"], "decimal");
     lazyNumberFormatData.style = s;
 
-    // Steps 17-20.
+    // Steps 16-19.
     var c = GetOption(options, "currency", "string", undefined, undefined);
     if (c !== undefined && !IsWellFormedCurrencyCode(c))
         ThrowRangeError(JSMSG_INVALID_CURRENCY_CODE, c);
@@ -1946,54 +1985,36 @@ function InitializeNumberFormat(numberFormat, locales, options) {
         if (c === undefined)
             ThrowTypeError(JSMSG_UNDEFINED_CURRENCY);
 
-        // Steps 20.a-c.
+        // Steps 19.a-c.
         c = toASCIIUpperCase(c);
         lazyNumberFormatData.currency = c;
         cDigits = CurrencyDigits(c);
     }
 
-    // Step 21.
+    // Step 20.
     var cd = GetOption(options, "currencyDisplay", "string", ["code", "symbol", "name"], "symbol");
     if (s === "currency")
         lazyNumberFormatData.currencyDisplay = cd;
 
-    // Step 23.
-    var mnid = GetNumberOption(options, "minimumIntegerDigits", 1, 21, 1);
-    lazyNumberFormatData.minimumIntegerDigits = mnid;
-
-    // Steps 25-26.
-    var mnfdDefault = (s === "currency") ? cDigits : 0;
-    var mnfd = GetNumberOption(options, "minimumFractionDigits", 0, 20, mnfdDefault);
-    lazyNumberFormatData.minimumFractionDigits = mnfd;
-
-    // Steps 28-29.
-    var mxfdDefault;
-    if (s === "currency")
-        mxfdDefault = std_Math_max(mnfd, cDigits);
-    else if (s === "percent")
-        mxfdDefault = std_Math_max(mnfd, 0);
-    else
-        mxfdDefault = std_Math_max(mnfd, 3);
-    var mxfd = GetNumberOption(options, "maximumFractionDigits", mnfd, 20, mxfdDefault);
-    lazyNumberFormatData.maximumFractionDigits = mxfd;
-
-    // Steps 31-32.
-    var mnsd = options.minimumSignificantDigits;
-    var mxsd = options.maximumSignificantDigits;
+    // Steps 22-24.
+    SetNumberFormatDigitOptions(lazyNumberFormatData, options, s === "currency" ? cDigits: 0);
 
-    // Step 33.
-    if (mnsd !== undefined || mxsd !== undefined) {
-        mnsd = GetNumberOption(options, "minimumSignificantDigits", 1, 21, 1);
-        mxsd = GetNumberOption(options, "maximumSignificantDigits", mnsd, 21, 21);
-        lazyNumberFormatData.minimumSignificantDigits = mnsd;
-        lazyNumberFormatData.maximumSignificantDigits = mxsd;
+    // Step 25.
+    if (lazyNumberFormatData.maximumFractionDigits === undefined) {
+        let mxfdDefault = s === "currency"
+                          ? cDigits
+                          : s === "percent"
+                          ? 0
+                          : 3;
+        lazyNumberFormatData.maximumFractionDigits =
+            std_Math_max(lazyNumberFormatData.minimumFractionDigits, mxfdDefault);
     }
 
-    // Step 34.
+    // Step 26.
     var g = GetOption(options, "useGrouping", "boolean", undefined, true);
     lazyNumberFormatData.useGrouping = g;
 
-    // Step 43.
+    // Steps 35-36.
     //
     // We've done everything that must be done now: mark the lazy data as fully
     // computed and install it.
@@ -2990,6 +3011,234 @@ function resolveICUPattern(pattern, result) {
     }
 }
 
+/********** Intl.PluralRules **********/
+
+/**
+ * PluralRules internal properties.
+ *
+ * Spec: ECMAScript 402 API, PluralRules, 1.3.3.
+ */
+var pluralRulesInternalProperties = {
+    _availableLocales: null,
+    availableLocales: function()
+    {
+        var locales = this._availableLocales;
+        if (locales)
+            return locales;
+
+        locales = intl_PluralRules_availableLocales();
+        addSpecialMissingLanguageTags(locales);
+        return (this._availableLocales = locales);
+    }
+};
+
+/**
+ * Compute an internal properties object from |lazyPluralRulesData|.
+ */
+function resolvePluralRulesInternals(lazyPluralRulesData) {
+    assert(IsObject(lazyPluralRulesData), "lazy data not an object?");
+
+    var internalProps = std_Object_create(null);
+
+    var requestedLocales = lazyPluralRulesData.requestedLocales;
+
+    var PluralRules = pluralRulesInternalProperties;
+
+    // Step 13.
+    const r = ResolveLocale(callFunction(PluralRules.availableLocales, PluralRules),
+                          lazyPluralRulesData.requestedLocales,
+                          lazyPluralRulesData.opt,
+                          noRelevantExtensionKeys, undefined);
+
+    // Step 14.
+    internalProps.locale = r.locale;
+    internalProps.type = lazyPluralRulesData.type;
+
+    internalProps.pluralCategories = intl_GetPluralCategories(
+        internalProps.locale,
+        internalProps.type);
+
+    internalProps.minimumIntegerDigits = lazyPluralRulesData.minimumIntegerDigits;
+    internalProps.minimumFractionDigits = lazyPluralRulesData.minimumFractionDigits;
+    internalProps.maximumFractionDigits = lazyPluralRulesData.maximumFractionDigits;
+
+    if ("minimumSignificantDigits" in lazyPluralRulesData) {
+        assert("maximumSignificantDigits" in lazyPluralRulesData, "min/max sig digits mismatch");
+        internalProps.minimumSignificantDigits = lazyPluralRulesData.minimumSignificantDigits;
+        internalProps.maximumSignificantDigits = lazyPluralRulesData.maximumSignificantDigits;
+    }
+
+    return internalProps;
+}
+
+/**
+ * Returns an object containing the PluralRules internal properties of |obj|,
+ * or throws a TypeError if |obj| isn't PluralRules-initialized.
+ */
+function getPluralRulesInternals(obj, methodName) {
+    var internals = getIntlObjectInternals(obj, "PluralRules", methodName);
+    assert(internals.type === "PluralRules", "bad type escaped getIntlObjectInternals");
+
+    var internalProps = maybeInternalProperties(internals);
+    if (internalProps)
+        return internalProps;
+
+    internalProps = resolvePluralRulesInternals(internals.lazyData);
+    setInternalProperties(internals, internalProps);
+    return internalProps;
+}
+
+/**
+ * Initializes an object as a PluralRules.
+ *
+ * This method is complicated a moderate bit by its implementing initialization
+ * as a *lazy* concept.  Everything that must happen now, does -- but we defer
+ * all the work we can until the object is actually used as a PluralRules.
+ * This later work occurs in |resolvePluralRulesInternals|; steps not noted
+ * here occur there.
+ *
+ * Spec: ECMAScript 402 API, PluralRules, 1.1.1.
+ */
+function InitializePluralRules(pluralRules, locales, options) {
+    assert(IsObject(pluralRules), "InitializePluralRules");
+
+    // Step 1.
+    if (isInitializedIntlObject(pluralRules))
+        ThrowTypeError(JSMSG_INTL_OBJECT_REINITED);
+
+    let internals = initializeIntlObject(pluralRules);
+
+    // Lazy PluralRules data has the following structure:
+    //
+    //   {
+    //     requestedLocales: List of locales,
+    //     type: "cardinal" / "ordinal",
+    //
+    //     opt: // opt object computer in InitializePluralRules
+    //       {
+    //         localeMatcher: "lookup" / "best fit",
+    //       }
+    //
+    //     minimumIntegerDigits: integer ∈ [1, 21],
+    //     minimumFractionDigits: integer ∈ [0, 20],
+    //     maximumFractionDigits: integer ∈ [0, 20],
+    //
+    //     // optional
+    //     minimumSignificantDigits: integer ∈ [1, 21],
+    //     maximumSignificantDigits: integer ∈ [1, 21],
+    //   }
+    //
+    // Note that lazy data is only installed as a final step of initialization,
+    // so every PluralRules lazy data object has *all* these properties, never a
+    // subset of them.
+    const lazyPluralRulesData = std_Object_create(null);
+
+    // Step 3.
+    let requestedLocales = CanonicalizeLocaleList(locales);
+    lazyPluralRulesData.requestedLocales = requestedLocales;
+
+    // Steps 4-5.
+    if (options === undefined)
+        options = {};
+    else
+        options = ToObject(options);
+
+    // Step 6.
+    const type = GetOption(options, "type", "string", ["cardinal", "ordinal"], "cardinal");
+    lazyPluralRulesData.type = type;
+
+    // Step 8.
+    let opt = new Record();
+    lazyPluralRulesData.opt = opt;
+
+    // Steps 9-10.
+    let matcher = GetOption(options, "localeMatcher", "string", ["lookup", "best fit"], "best fit");
+    opt.localeMatcher = matcher;
+
+
+    // Step 11.
+    SetNumberFormatDigitOptions(lazyPluralRulesData, options, 0);
+
+    // Step 12.
+    if (lazyPluralRulesData.maximumFractionDigits === undefined) {
+        lazyPluralRulesData.maximumFractionDigits =
+           std_Math_max(lazyPluralRulesData.minimumFractionDigits, 3);
+    }
+
+    setLazyData(internals, "PluralRules", lazyPluralRulesData)
+}
+
+/**
+ * Returns the subset of the given locale list for which this locale list has a
+ * matching (possibly fallback) locale. Locales appear in the same order in the
+ * returned list as in the input list.
+ *
+ * Spec: ECMAScript 402 API, PluralRules, 1.3.2.
+ */
+function Intl_PluralRules_supportedLocalesOf(locales /*, options*/) {
+    var options = arguments.length > 1 ? arguments[1] : undefined;
+
+    // Step 1.
+    var availableLocales = callFunction(pluralRulesInternalProperties.availableLocales,
+                                        pluralRulesInternalProperties);
+    // Step 2.
+    let requestedLocales = CanonicalizeLocaleList(locales);
+
+    // Step 3.
+    return SupportedLocales(availableLocales, requestedLocales, options);
+}
+
+/**
+ * Returns a String value representing the plural category matching
+ * the number passed as value according to the
+ * effective locale and the formatting options of this PluralRules.
+ *
+ * Spec: ECMAScript 402 API, PluralRules, 1.4.3.
+ */
+function Intl_PluralRules_select(value) {
+    // Step 1.
+    let pluralRules = this;
+    // Step 2.
+    let internals = getPluralRulesInternals(pluralRules, "select");
+
+    // Steps 3-4.
+    let n = ToNumber(value);
+
+    // Step 5.
+    return intl_SelectPluralRule(pluralRules, n);
+}
+
+/**
+ * Returns the resolved options for a PluralRules object.
+ *
+ * Spec: ECMAScript 402 API, PluralRules, 1.4.4.
+ */
+function Intl_PluralRules_resolvedOptions() {
+    var internals = getPluralRulesInternals(this, "resolvedOptions");
+
+    var result = {
+        locale: internals.locale,
+        type: internals.type,
+        pluralCategories: callFunction(std_Array_slice, internals.pluralCategories, 0),
+        minimumIntegerDigits: internals.minimumIntegerDigits,
+        minimumFractionDigits: internals.minimumFractionDigits,
+        maximumFractionDigits: internals.maximumFractionDigits,
+    };
+
+    var optionalProperties = [
+        "minimumSignificantDigits",
+        "maximumSignificantDigits"
+    ];
+
+    for (var i = 0; i < optionalProperties.length; i++) {
+        var p = optionalProperties[i];
+        if (callFunction(std_Object_hasOwnProperty, internals, p))
+            _DefineDataProperty(result, p, internals[p]);
+    }
+    return result;
+}
+
+
 function Intl_getCanonicalLocales(locales) {
   let codes = CanonicalizeLocaleList(locales);
   let result = [];
diff --git a/js/src/vm/CommonPropertyNames.h b/js/src/vm/CommonPropertyNames.h
index 789a573dc..a88406bc6 100644
--- a/js/src/vm/CommonPropertyNames.h
+++ b/js/src/vm/CommonPropertyNames.h
@@ -178,6 +178,7 @@
     macro(InitializeCollator, InitializeCollator, "InitializeCollator") \
     macro(InitializeDateTimeFormat, InitializeDateTimeFormat, "InitializeDateTimeFormat") \
     macro(InitializeNumberFormat, InitializeNumberFormat, "InitializeNumberFormat") \
+    macro(InitializePluralRules, InitializePluralRules, "InitializePluralRules") \
     macro(innermost, innermost, "innermost") \
     macro(inNursery, inNursery, "inNursery") \
     macro(input, input, "input") \
@@ -270,6 +271,8 @@
     macro(parseInt, parseInt, "parseInt") \
     macro(pattern, pattern, "pattern") \
     macro(pending, pending, "pending") \
+    macro(PluralRules, PluralRules, "PluralRules") \
+    macro(PluralRulesSelect, PluralRulesSelect, "Intl_PluralRules_Select") \
     macro(public, public_, "public") \
     macro(preventExtensions, preventExtensions, "preventExtensions") \
     macro(private, private_, "private") \
diff --git a/js/src/vm/GlobalObject.h b/js/src/vm/GlobalObject.h
index 011f90aa1..f9c0149f1 100644
--- a/js/src/vm/GlobalObject.h
+++ b/js/src/vm/GlobalObject.h
@@ -109,6 +109,7 @@ class GlobalObject : public NativeObject
         COLLATOR_PROTO,
         NUMBER_FORMAT_PROTO,
         DATE_TIME_FORMAT_PROTO,
+        PLURAL_RULES_PROTO,
         MODULE_PROTO,
         IMPORT_ENTRY_PROTO,
         EXPORT_ENTRY_PROTO,
@@ -507,6 +508,11 @@ class GlobalObject : public NativeObject
         return getOrCreateObject(cx, global, DATE_TIME_FORMAT_PROTO, initIntlObject);
     }
 
+    static JSObject*
+    getOrCreatePluralRulesPrototype(JSContext* cx, Handle<GlobalObject*> global) {
+        return getOrCreateObject(cx, global, PLURAL_RULES_PROTO, initIntlObject);
+    }
+
     static bool ensureModulePrototypesCreated(JSContext *cx, Handle<GlobalObject*> global);
 
     JSObject* maybeGetModulePrototype() {
diff --git a/js/src/vm/SelfHosting.cpp b/js/src/vm/SelfHosting.cpp
index dc1dfb9fa..df326a69e 100644
--- a/js/src/vm/SelfHosting.cpp
+++ b/js/src/vm/SelfHosting.cpp
@@ -2605,6 +2605,9 @@ static const JSFunctionSpec intrinsic_functions[] = {
     JS_FN("intl_NumberFormat_availableLocales", intl_NumberFormat_availableLocales, 0,0),
     JS_FN("intl_numberingSystem", intl_numberingSystem, 1,0),
     JS_FN("intl_patternForSkeleton", intl_patternForSkeleton, 2,0),
+    JS_FN("intl_PluralRules_availableLocales", intl_PluralRules_availableLocales, 0,0),
+    JS_FN("intl_GetPluralCategories", intl_GetPluralCategories, 2, 0),
+    JS_FN("intl_SelectPluralRule", intl_SelectPluralRule, 2,0),
 
     JS_INLINABLE_FN("IsRegExpObject",
                     intrinsic_IsInstanceOfBuiltin<RegExpObject>, 1,0,