Expose getCanonicalLocales() for Intl object

src/js/i18n.js

Index: src/js/i18n.js
diff --git a/src/js/i18n.js b/src/js/i18n.js
index 6d38a3f2db194c5c1f262dbfa4d0b88599f3f7af..1cfb296e9c0fccdd0ebbc3366b2623a6518d4d0d 100644
--- a/src/js/i18n.js
+++ b/src/js/i18n.js
@@ -718,6 +718,7 @@ function toTitleCaseTimezoneLocation(location) {
 
 /**
  * Canonicalizes the language tag, or throws in case the tag is invalid.
+ * ECMA 402 9.2.1 steps 7.c ii ~ v.
  */
 function canonicalizeLanguageTag(localeID) {
   // null is typeof 'object' so we have to do extra check.
@@ -735,11 +736,14 @@ function canonicalizeLanguageTag(localeID) {
 
   var localeString = TO_STRING(localeID);
 
-  if (isValidLanguageTag(localeString) === false) {
+  if (isStructuallyValidLanguageTag(localeString) === false) {
     throw %make_range_error(kInvalidLanguageTag, localeString);
   }
 
+  // ECMA 402 6.2.3
   var tag = %CanonicalizeLanguageTag(localeString);
+  // TODO(jshin): This should not happen because the structual validity
+  // is already checked. If that's the case, remove this.
   if (tag === 'invalid-tag') {
     throw %make_range_error(kInvalidLanguageTag, localeString);
   }
@@ -751,6 +755,7 @@ function canonicalizeLanguageTag(localeID) {
 /**
  * Returns an array where all locales are canonicalized and duplicates removed.
  * Throws on locales that are not well formed BCP47 tags.
+ * ECMA 402 8.2.1 steps 1 (ECMA 402 9.2.1) and 2.
  */
 function initializeLocaleList(locales) {
   var seen = new InternalArray();
@@ -762,7 +767,7 @@ function initializeLocaleList(locales) {
     }
 
     var o = TO_OBJECT(locales);
-    var len = TO_UINT32(o.length);
+    var len = TO_LENGTH(o.length);
 
     for (var k = 0; k < len; k++) {
       if (k in o) {
@@ -782,15 +787,22 @@ function initializeLocaleList(locales) {
 
 
 /**
- * Validates the language tag. Section 2.2.9 of the bcp47 spec
- * defines a valid tag.
+ * Check the structual Validity of the language tag per ECMA 402 6.2.2:
+ *   - Well-formed per RFC 5646 2.1
+ *   - There are no duplicate variant subtags
+ *   - There are no duplicate singletion (extension) subtags
+ *
+ * One extra-check is done (from RFC 5646 2.2.9): the tag is compared
+ * against the list of grandfathered tags. However, subtags for
+ * primary/extended language, script, region, variant are not checked
+ * against the IANA language subtag registry.
  *
  * ICU is too permissible and lets invalid tags, like
  * hant-cmn-cn, through.
  *
  * Returns false if the language tag is invalid.
  */
-function isValidLanguageTag(locale) {
+function isStructuallyValidLanguageTag(locale) {
   // Check if it's well-formed, including grandfadered tags.
   if (IS_NULL(InternalRegExpMatch(GetLanguageTagRE(), locale))) {
     return false;
@@ -885,6 +897,16 @@ var resolvedAccessor = {
   }
 };
 
+// ECMA 402 section 8.2.1
+InstallFunction(Intl, 'getCanonicalLocales', function(locales) {
+    if (!IS_UNDEFINED(new.target)) {
+      throw %make_type_error(kOrdinaryFunctionCalledAsConstructor);
+    }
+
+    return initializeLocaleList(locales);

[Dan Ehrenberg, 2016/08/11 21:07:01]

This outputs a frozen Array, but the spec indicates a full, ordinary mutable
Array. In addition to fixing the bug here, it'd be nice to file a bug against
test262 to ask for tests of this property, given that what you've done here is a
pretty natural implementation strategy.

+  }
+);
+
 /**
  * Initializes the given object so it's a valid Collator instance.
  * Useful for subclassing.