Add pluralrules to JS Intl

1 files changed, 492 insertions, 134 deletions

diff --git a/js/src/builtin/Intl.js b/js/src/builtin/Intl.js
index 493062c1c6..37c87365b3 100644
--- a/js/src/builtin/Intl.js
+++ b/js/src/builtin/Intl.js
@@ -9,7 +9,8 @@
          JSMSG_INVALID_OPTION_VALUE: false, JSMSG_INVALID_DIGITS_VALUE: false,
          JSMSG_INTL_OBJECT_REINITED: false, JSMSG_INVALID_CURRENCY_CODE: false,
          JSMSG_UNDEFINED_CURRENCY: false, JSMSG_INVALID_TIME_ZONE: false,
-         JSMSG_DATE_NOT_FINITE: false,
+         JSMSG_DATE_NOT_FINITE: false, JSMSG_INVALID_KEYS_TYPE: false,
+         JSMSG_INVALID_KEY: false,
          intl_Collator_availableLocales: false,
          intl_availableCollations: false,
          intl_CompareStrings: false,
@@ -20,6 +21,9 @@
          intl_availableCalendars: false,
          intl_patternForSkeleton: false,
          intl_FormatDateTime: false,
+         intl_SelectPluralRule: false,
+         intl_GetPluralCategories: false,
+         intl_GetCalendarInfo: false,
 */
 
 /*
@@ -432,7 +436,7 @@ function CanonicalizeLanguageTag(locale) {
         subtags[i] = subtag;
         i++;
     }
-    var normal = callFunction(std_Array_join, callFunction(std_Array_slice, subtags, 0, i), "-");
+    var normal = ArrayJoinRange(subtags, "-", 0, i);
 
     // Extension sequences are sorted by their singleton characters.
     // "u-ca-chinese-t-zh-latn" -> "t-zh-latn-u-ca-chinese"
@@ -442,7 +446,7 @@ function CanonicalizeLanguageTag(locale) {
         i++;
         while (i < subtags.length && subtags[i].length > 1)
             i++;
-        var extension = callFunction(std_Array_join, callFunction(std_Array_slice, subtags, extensionStart, i), "-");
+        var extension = ArrayJoinRange(subtags, "-", extensionStart, i);
         callFunction(std_Array_push, extensions, extension);
     }
     callFunction(std_Array_sort, extensions);
@@ -450,7 +454,7 @@ function CanonicalizeLanguageTag(locale) {
     // Private use sequences are left as is. "x-private"
     var privateUse = "";
     if (i < subtags.length)
-        privateUse = callFunction(std_Array_join, callFunction(std_Array_slice, subtags, i), "-");
+        privateUse = ArrayJoinRange(subtags, "-", i);
 
     // Put everything back together.
     var canonical = normal;
@@ -467,6 +471,24 @@ function CanonicalizeLanguageTag(locale) {
     return canonical;
 }
 
+/**
+ * Joins the array elements in the given range with the supplied separator.
+ */
+function ArrayJoinRange(array, separator, from, to = array.length) {
+    assert(typeof separator === "string", "|separator| is a string value");
+    assert(typeof from === "number", "|from| is a number value");
+    assert(typeof to === "number", "|to| is a number value");
+    assert(0 <= from && from <= to && to <= array.length, "|from| and |to| form a valid range");
+
+    if (from === to)
+        return "";
+
+    var result = array[from];
+    for (var i = from + 1; i < to; i++) {
+        result += separator + array[i];
+    }
+    return result;
+}
 
 function localeContainsNoUnicodeExtensions(locale) {
     // No "-u-", no possible Unicode extension.
@@ -838,6 +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
@@ -1165,9 +1188,10 @@ function GetOption(options, property, type, values, fallback) {
  * Spec: ECMAScript Internationalization API Specification, 9.2.10.
  */
 function GetNumberOption(options, property, minimum, maximum, fallback) {
-    assert(typeof minimum === "number", "GetNumberOption");
-    assert(typeof maximum === "number", "GetNumberOption");
-    assert(fallback === undefined || (fallback >= minimum && fallback <= maximum), "GetNumberOption");
+    assert(typeof minimum === "number" && (minimum | 0) === minimum, "GetNumberOption");
+    assert(typeof maximum === "number" && (maximum | 0) === maximum, "GetNumberOption");
+    assert(typeof fallback === "number" && (fallback | 0) === fallback, "GetNumberOption");
+    assert(minimum <= fallback && fallback <= maximum, "GetNumberOption");
 
     // Step 1.
     var value = options[property];
@@ -1177,7 +1201,10 @@ function GetNumberOption(options, property, minimum, maximum, fallback) {
         value = ToNumber(value);
         if (Number_isNaN(value) || value < minimum || value > maximum)
             ThrowRangeError(JSMSG_INVALID_DIGITS_VALUE, value);
-        return std_Math_floor(value);
+
+        // Apply bitwise-or to convert -0 to +0 per ES2017, 5.2 and to ensure
+        // the result is an int32 value.
+        return std_Math_floor(value) | 0;
     }
 
     // Step 3.
@@ -1251,7 +1278,9 @@ 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.
@@ -1301,7 +1330,9 @@ 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 {
@@ -1358,6 +1389,8 @@ 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);
@@ -1689,6 +1722,7 @@ function Intl_Collator_compare_get() {
     // Step 2.
     return internals.boundCompare;
 }
+_SetCanonicalName(Intl_Collator_compare_get, "get compare");
 
 
 /**
@@ -1757,45 +1791,37 @@ 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.
-    var s = lazyNumberFormatData.style;
-    internalProps.style = s;
+    // Step 15.
+    var style = lazyNumberFormatData.style;
+    internalProps.style = style;
 
-    // Steps 20, 22.
-    if (s === "currency") {
+    // Steps 19, 21.
+    if (style === "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.
@@ -1804,10 +1830,10 @@ 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
@@ -1835,6 +1861,44 @@ 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, mxfdDefault) {
+    // 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");
+    assert(typeof mxfdDefault === "number", "SetNumberFormatDigitOptions");
+    assert(mnfdDefault <= mxfdDefault, "SetNumberFormatDigitOptions");
+
+    // Steps 4-6.
+    const mnid = GetNumberOption(options, "minimumIntegerDigits", 1, 21, 1);
+    const mnfd = GetNumberOption(options, "minimumFractionDigits", 0, 20, mnfdDefault);
+    const mxfdActualDefault = std_Math_max(mnfd, mxfdDefault);
+    const mxfd = GetNumberOption(options, "maximumFractionDigits", mnfd, 20, mxfdActualDefault);
+
+    // 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.
@@ -1884,7 +1948,7 @@ 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);
 
@@ -1914,67 +1978,46 @@ function InitializeNumberFormat(numberFormat, locales, options) {
     opt.localeMatcher = matcher;
 
     // Compute formatting options.
-    // Step 15.
-    var s = GetOption(options, "style", "string", ["decimal", "percent", "currency"], "decimal");
-    lazyNumberFormatData.style = s;
+    // Step 14.
+    var style = GetOption(options, "style", "string", ["decimal", "percent", "currency"], "decimal");
+    lazyNumberFormatData.style = style;
 
-    // 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);
     var cDigits;
-    if (s === "currency") {
+    if (style === "currency") {
         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")
+    if (style === "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;
-
-    // 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;
+    // Steps 22-25.
+    var mnfdDefault, mxfdDefault;
+    if (style === "currency") {
+        mnfdDefault = cDigits;
+        mxfdDefault = cDigits;
+    } else {
+        mnfdDefault = 0;
+        mxfdDefault = style === "percent" ? 0 : 3;
     }
+    SetNumberFormatDigitOptions(lazyNumberFormatData, options, mnfdDefault, mxfdDefault);
 
-    // Step 34.
+    // Steps 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.
@@ -1983,43 +2026,6 @@ function InitializeNumberFormat(numberFormat, locales, options) {
 
 
 /**
- * Mapping from currency codes to the number of decimal digits used for them.
- * Default is 2 digits.
- *
- * Spec: ISO 4217 Currency and Funds Code List.
- * http://www.currency-iso.org/en/home/tables/table-a1.html
- */
-var currencyDigits = {
-    BHD: 3,
-    BIF: 0,
-    BYR: 0,
-    CLF: 4,
-    CLP: 0,
-    DJF: 0,
-    GNF: 0,
-    IQD: 3,
-    ISK: 0,
-    JOD: 3,
-    JPY: 0,
-    KMF: 0,
-    KRW: 0,
-    KWD: 3,
-    LYD: 3,
-    OMR: 3,
-    PYG: 0,
-    RWF: 0,
-    TND: 3,
-    UGX: 0,
-    UYI: 0,
-    VND: 0,
-    VUV: 0,
-    XAF: 0,
-    XOF: 0,
-    XPF: 0
-};
-
-
-/**
  * Returns the number of decimal digits to be used for the given currency.
  *
  * Spec: ECMAScript Internationalization API Specification, 11.1.1.
@@ -2100,7 +2106,7 @@ function numberFormatFormatToBind(value) {
 
     // Step 1.a.ii-iii.
     var x = ToNumber(value);
-    return intl_FormatNumber(this, x);
+    return intl_FormatNumber(this, x, /* formatToParts = */ false);
 }
 
 
@@ -2127,6 +2133,22 @@ function Intl_NumberFormat_format_get() {
     // Step 2.
     return internals.boundFormat;
 }
+_SetCanonicalName(Intl_NumberFormat_format_get, "get format");
+
+
+function Intl_NumberFormat_formatToParts(value) {
+    // Step 1.
+    var nf = this;
+
+    // Steps 2-3.
+    getNumberFormatInternals(nf, "formatToParts");
+
+    // Step 4.
+    var x = ToNumber(value);
+
+    // Step 5.
+    return intl_FormatNumber(nf, x, /* formatToParts = */ true);
+}
 
 
 /**
@@ -2268,26 +2290,6 @@ function getDateTimeFormatInternals(obj, methodName) {
     return internalProps;
 }
 
-/**
- * Components of date and time formats and their values.
- *
- * Spec: ECMAScript Internationalization API Specification, 12.1.1.
- */
-var dateTimeComponentValues = {
-    weekday: ["narrow", "short", "long"],
-    era: ["narrow", "short", "long"],
-    year: ["2-digit", "numeric"],
-    month: ["2-digit", "numeric", "narrow", "short", "long"],
-    day: ["2-digit", "numeric"],
-    hour: ["2-digit", "numeric"],
-    minute: ["2-digit", "numeric"],
-    second: ["2-digit", "numeric"],
-    timeZoneName: ["short", "long"]
-};
-
-
-var dateTimeComponents = std_Object_getOwnPropertyNames(dateTimeComponentValues);
-
 
 /**
  * Initializes an object as a DateTimeFormat.
@@ -2377,12 +2379,19 @@ function InitializeDateTimeFormat(dateTimeFormat, locales, options) {
     lazyDateTimeFormatData.formatOpt = formatOpt;
 
     // Step 19.
-    var i, prop;
-    for (i = 0; i < dateTimeComponents.length; i++) {
-        prop = dateTimeComponents[i];
-        var value = GetOption(options, prop, "string", dateTimeComponentValues[prop], undefined);
-        formatOpt[prop] = value;
-    }
+    // 12.1, Table 4: Components of date and time formats.
+    formatOpt.weekday = GetOption(options, "weekday", "string", ["narrow", "short", "long"],
+                                  undefined);
+    formatOpt.era = GetOption(options, "era", "string", ["narrow", "short", "long"], undefined);
+    formatOpt.year = GetOption(options, "year", "string", ["2-digit", "numeric"], undefined);
+    formatOpt.month = GetOption(options, "month", "string",
+                                ["2-digit", "numeric", "narrow", "short", "long"], undefined);
+    formatOpt.day = GetOption(options, "day", "string", ["2-digit", "numeric"], undefined);
+    formatOpt.hour = GetOption(options, "hour", "string", ["2-digit", "numeric"], undefined);
+    formatOpt.minute = GetOption(options, "minute", "string", ["2-digit", "numeric"], undefined);
+    formatOpt.second = GetOption(options, "second", "string", ["2-digit", "numeric"], undefined);
+    formatOpt.timeZoneName = GetOption(options, "timeZoneName", "string", ["short", "long"],
+                                       undefined);
 
     // Steps 20-21 provided by ICU - see comment after this function.
 
@@ -2650,7 +2659,6 @@ function ToDateTimeOptions(options, required, defaults) {
     return options;
 }
 
-
 /**
  * Compares the date and time components requested by options with the available
  * date and time formats in formats, and selects the best match according
@@ -2836,6 +2844,7 @@ function Intl_DateTimeFormat_format_get() {
     // Step 2.
     return internals.boundFormat;
 }
+_SetCanonicalName(Intl_DateTimeFormat_format_get, "get format");
 
 
 function Intl_DateTimeFormat_formatToParts() {
@@ -2971,6 +2980,232 @@ 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;
+
+    // Steps 11-12.
+    SetNumberFormatDigitOptions(lazyPluralRulesData, options, 0, 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 internalsPluralCategories = internals.pluralCategories;
+    var pluralCategories = [];
+    for (var i = 0; i < internalsPluralCategories.length; i++)
+        _DefineDataProperty(pluralCategories, i, internalsPluralCategories[i]);
+
+    var result = {
+        locale: internals.locale,
+        type: internals.type,
+        pluralCategories,
+        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 = [];
@@ -3006,3 +3241,126 @@ function Intl_getCalendarInfo(locales) {
 
   return result;
 }
+
+/**
+ * This function is a custom method designed after Intl API, but currently
+ * not part of the spec or spec proposal.
+ * We want to use it internally to retrieve translated values from CLDR in
+ * order to ensure they're aligned with what Intl API returns.
+ *
+ * This API may one day be a foundation for an ECMA402 API spec proposal.
+ *
+ * The function takes two arguments - locales which is a list of locale strings
+ * and options which is an object with two optional properties:
+ *
+ *   keys:
+ *     an Array of string values that are paths to individual terms
+ *
+ *   style:
+ *     a String with a value "long", "short" or "narrow"
+ *
+ * It returns an object with properties:
+ *
+ *   locale:
+ *     a negotiated locale string
+ *
+ *   style:
+ *     negotiated style
+ *
+ *   values:
+ *     A key-value pair list of requested keys and corresponding
+ *     translated values
+ *
+ */
+function Intl_getDisplayNames(locales, options) {
+    // 1. Let requestLocales be ? CanonicalizeLocaleList(locales).
+    const requestedLocales = CanonicalizeLocaleList(locales);
+
+    // 2. If options is undefined, then
+    if (options === undefined)
+        // a. Let options be ObjectCreate(%ObjectPrototype%).
+        options = {};
+    // 3. Else,
+    else
+        // a. Let options be ? ToObject(options).
+        options = ToObject(options);
+
+    const DateTimeFormat = dateTimeFormatInternalProperties;
+
+    // 4. Let localeData be %DateTimeFormat%.[[localeData]].
+    const localeData = DateTimeFormat.localeData;
+
+    // 5. Let opt be a new Record.
+    const localeOpt = new Record();
+    // 6. Set localeOpt.[[localeMatcher]] to "best fit".
+    localeOpt.localeMatcher = "best fit";
+
+    // 7. Let r be ResolveLocale(%DateTimeFormat%.[[availableLocales]], requestedLocales, localeOpt,
+    //    %DateTimeFormat%.[[relevantExtensionKeys]], localeData).
+    const r = ResolveLocale(callFunction(DateTimeFormat.availableLocales, DateTimeFormat),
+                          requestedLocales,
+                          localeOpt,
+                          DateTimeFormat.relevantExtensionKeys,
+                          localeData);
+
+    // 8. Let style be ? GetOption(options, "style", "string", « "long", "short", "narrow" », "long").
+    const style = GetOption(options, "style", "string", ["long", "short", "narrow"], "long");
+    // 9. Let keys be ? Get(options, "keys").
+    let keys = options.keys;
+
+    // 10. If keys is undefined,
+    if (keys === undefined) {
+        // a. Let keys be ArrayCreate(0).
+        keys = [];
+    } else if (!IsObject(keys)) {
+        // 11. Else,
+        //   a. If Type(keys) is not Object, throw a TypeError exception.
+        ThrowTypeError(JSMSG_INVALID_KEYS_TYPE);
+    }
+
+    // 12. Let processedKeys be ArrayCreate(0).
+    // (This really should be a List, but we use an Array here in order that
+    // |intl_ComputeDisplayNames| may infallibly access the list's length via
+    // |ArrayObject::length|.)
+    let processedKeys = [];
+    // 13. Let len be ? ToLength(? Get(keys, "length")).
+    let len = ToLength(keys.length);
+    // 14. Let i be 0.
+    // 15. Repeat, while i < len
+    for (let i = 0; i < len; i++) {
+        // a. Let processedKey be ? ToString(? Get(keys, i)).
+        // b. Perform ? CreateDataPropertyOrThrow(processedKeys, i, processedKey).
+        callFunction(std_Array_push, processedKeys, ToString(keys[i]));
+    }
+
+    // 16. Let names be ? ComputeDisplayNames(r.[[locale]], style, processedKeys).
+    const names = intl_ComputeDisplayNames(r.locale, style, processedKeys);
+
+    // 17. Let values be ObjectCreate(%ObjectPrototype%).
+    const values = {};
+
+    // 18. Set i to 0.
+    // 19. Repeat, while i < len
+    for (let i = 0; i < len; i++) {
+        // a. Let key be ? Get(processedKeys, i).
+        const key = processedKeys[i];
+        // b. Let name be ? Get(names, i).
+        const name = names[i];
+        // c. Assert: Type(name) is string.
+        assert(typeof name === "string", "unexpected non-string value");
+        // d. Assert: the length of name is greater than zero.
+        assert(name.length > 0, "empty string value");
+        // e. Perform ? DefinePropertyOrThrow(values, key, name).
+        _DefineDataProperty(values, key, name);
+    }
+
+    // 20. Let options be ObjectCreate(%ObjectPrototype%).
+    // 21. Perform ! DefinePropertyOrThrow(result, "locale", r.[[locale]]).
+    // 22. Perform ! DefinePropertyOrThrow(result, "style", style).
+    // 23. Perform ! DefinePropertyOrThrow(result, "values", values).
+    const result = { locale: r.locale, style, values };
+
+    // 24. Return result.
+    return result;
+}
+