Simplify ParseTemporalTimeZoneString

This was a bit of a mess. Rewrite the operation so that it tries to parse
the string as a bare time zone identifier _first_, and if that fails,
as an ISO string, throwing if the ISO string doesn't contain any time zone
(whether Z designator, UTC offset, or IANA name).

This was what the operation previously did, just much more difficult to
follow.

The reference polyfill mostly already worked like this, but move the
IANA name canonicalization step out of ParseTemporalTimeZoneString and
into its only caller, to correspond better with the spec text. This also
requires bringing the time zone ID regex better in line with the grammar's
|TimeZoneIdentifier| production by adding the IANA legacy names.

UPSTREAM_COMMIT=eec8efab983131401c2092dd26a1f9e8d049b666

Author: ptomato

lib/ecmascript.ts

@@ -343,8 +343,8 @@ export function RejectObjectWithCalendarOrTimeZone(item: AnyTemporalLikeType) {
   }
 }
 function ParseTemporalTimeZone(stringIdent: string) {
-  let { ianaName, offset, z } = ParseTemporalTimeZoneString(stringIdent);
-  if (ianaName) return ianaName;
+  const { ianaName, offset, z } = ParseTemporalTimeZoneString(stringIdent);
+  if (ianaName) return GetCanonicalTimeZoneIdentifier(ianaName);
   if (z) return 'UTC';
   return offset as string; // if !ianaName && !z then offset must be present
 }
@@ -533,12 +533,8 @@ export function ParseTemporalTimeZoneString(stringIdent: string): Partial<{
   offset: string | undefined;
   z: boolean | undefined;
 }> {
-  try {
-    let canonicalIdent = GetCanonicalTimeZoneIdentifier(stringIdent);
-    if (canonicalIdent) return { ianaName: canonicalIdent.toString() };
-  } catch {
-    // fall through
-  }
+  const bareID = new RegExp(`^${PARSE.timeZoneID.source}$`, 'i');
+  if (bareID.test(stringIdent)) return { ianaName: stringIdent };
   try {
     // Try parsing ISO string instead
     const result = ParseISODateTime(stringIdent);

lib/regex.ts

@@ -1,7 +1,18 @@
 const tzComponent = /\.[-A-Za-z_]|\.\.[-A-Za-z._]{1,12}|\.[-A-Za-z_][-A-Za-z._]{0,12}|[A-Za-z_][-A-Za-z._]{0,13}/;
 const offsetNoCapture = /(?:[+\u2212-][0-2][0-9](?::?[0-5][0-9](?::?[0-5][0-9](?:[.,]\d{1,9})?)?)?)/;
-const timeZoneID = new RegExp(
-  `(?:(?:${tzComponent.source})(?:\\/(?:${tzComponent.source}))*|Etc/GMT[-+]\\d{1,2}|${offsetNoCapture.source})`
+export const timeZoneID = new RegExp(
+  '(?:' +
+    [
+      `(?:${tzComponent.source})(?:\\/(?:${tzComponent.source}))*`,
+      'Etc/GMT(?:0|[-+]\\d{1,2})',
+      'GMT[-+]?0',
+      'EST5EDT',
+      'CST6CDT',
+      'MST7MDT',
+      'PST8PDT',
+      offsetNoCapture.source
+    ].join('|') +
+    ')'
 );
 
 const calComponent = /[A-Za-z0-9]{3,8}/;

test/validStrings.mjs

@@ -265,7 +265,7 @@ const timeZoneUTCOffsetName = seq(
 const timeZoneIANAName = choice(...timezoneNames);
 const timeZoneIdentifier = withCode(
   choice(timeZoneUTCOffsetName, timeZoneIANAName),
-  (data, result) => (data.ianaName = ES.GetCanonicalTimeZoneIdentifier(result).toString())
+  (data, result) => (data.ianaName = result)
 );
 const timeZoneBracketedAnnotation = seq('[', timeZoneIdentifier, ']');
 const timeZoneOffsetRequired = withCode(seq(timeZoneUTCOffset, [timeZoneBracketedAnnotation]), (data) => {