Editorial: Use early errors to simplify time-only grammar

Previously the grammar relied on bizarre one-off productions such as TimeSpecWithOptionalOffsetNotAmbiguous and DateMonthWithThirtyOneDays, to prevent time strings such as 0119 (01:19 but ambiguous with 19th January) or 1524-08 (15:24 at -08:00 from UTC, but ambiguous with August of 1524) from parsing correctly without a time designator. By using early errors, these confusing productions are no longer necessary to achieve the desired result. Closes: #1984
tc39 · Jun 13, 2024 · c30c407 · c30c407
1 parent 9e9a7f7
commit c30c407
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Showing 2 changed files with 25 additions and 23 deletions.
diff --git a/polyfill/test/validStrings.mjs b/polyfill/test/validStrings.mjs
@@ -285,14 +285,6 @@ const timeSpec = seq(
   timeHour,
   choice([':', timeMinute, [':', timeSecond, [timeFraction]]], seq(timeMinute, [timeSecond, [timeFraction]]))
 );
-const timeSpecWithOptionalOffsetNotAmbiguous = withSyntaxConstraints(seq(timeSpec, [dateTimeUTCOffset]), (result) => {
-  if (/^(?:(?!02-?30)(?:0[1-9]|1[012])-?(?:0[1-9]|[12][0-9]|30)|(?:0[13578]|10|12)-?31)$/.test(result)) {
-    throw new SyntaxError('valid PlainMonthDay');
-  }
-  if (/^(?![−-]000000)(?:[0-9]{4}|[+−-][0-9]{6})-?(?:0[1-9]|1[012])$/.test(result)) {
-    throw new SyntaxError('valid PlainYearMonth');
-  }
-});
 
 function validateDayOfMonth(result, { year, month, day }) {
   if (day > ES.ISODaysInMonth(year, month)) throw SyntaxError('retry if bad day of month');
@@ -306,7 +298,18 @@ const date = withSyntaxConstraints(
 const dateTime = seq(date, [dateTimeSeparator, timeSpec, [dateTimeUTCOffset]]);
 const annotatedTime = choice(
   seq(timeDesignator, timeSpec, [dateTimeUTCOffset], [timeZoneAnnotation], [annotations]),
-  seq(timeSpecWithOptionalOffsetNotAmbiguous, [timeZoneAnnotation], [annotations])
+  seq(
+    withSyntaxConstraints(seq(timeSpec, [dateTimeUTCOffset]), (result) => {
+      if (/^(?:(?!02-?30)(?:0[1-9]|1[012])-?(?:0[1-9]|[12][0-9]|30)|(?:0[13578]|10|12)-?31)$/.test(result)) {
+        throw new SyntaxError('valid PlainMonthDay');
+      }
+      if (/^(?![−-]000000)(?:[0-9]{4}|[+−-][0-9]{6})-?(?:0[1-9]|1[012])$/.test(result)) {
+        throw new SyntaxError('valid PlainYearMonth');
+      }
+    }),
+    [timeZoneAnnotation],
+    [annotations]
+  )
 );
 const annotatedDateTime = seq(dateTime, [timeZoneAnnotation], [annotations]);
 const annotatedDateTimeTimeRequired = seq(

diff --git a/spec/abstractops.html b/spec/abstractops.html
@@ -1239,9 +1239,6 @@ <h1>ISO 8601 grammar</h1>
           `11`
           `12`
 
-      DateMonthWithThirtyOneDays ::: one of
-          `01` `03` `05` `07` `08` `10` `12`
-
       DateDay :::
           `0` NonZeroDigit
           `1` DecimalDigit
@@ -1256,13 +1253,6 @@ <h1>ISO 8601 grammar</h1>
           `--` DateMonth `-`? DateDay
           DateMonth `-`? DateDay
 
-      ValidMonthDay :::
-          DateMonth `-`? `0` NonZeroDigit
-          DateMonth `-`? `1` DecimalDigit
-          DateMonth `-`? `2` DecimalDigit
-          DateMonth `-`? `30` but not one of `0230` or `02-30`
-          DateMonthWithThirtyOneDays `-`? `31`
-
       Date :::
           DateYear `-` DateMonth `-` DateDay
           DateYear DateMonth DateDay
@@ -1363,16 +1353,13 @@ <h1>ISO 8601 grammar</h1>
           TimeHour `:` TimeMinute `:` TimeSecond TimeFraction?
           TimeHour TimeMinute TimeSecond TimeFraction?
 
-      TimeSpecWithOptionalOffsetNotAmbiguous :::
-          TimeSpec DateTimeUTCOffset? but not one of ValidMonthDay or DateSpecYearMonth
-
       DateTime :::
           Date
           Date DateTimeSeparator TimeSpec DateTimeUTCOffset?
 
       AnnotatedTime :::
           TimeDesignator TimeSpec DateTimeUTCOffset? TimeZoneAnnotation? Annotations?
-          TimeSpecWithOptionalOffsetNotAmbiguous TimeZoneAnnotation? Annotations?
+          TimeSpec DateTimeUTCOffset? TimeZoneAnnotation? Annotations?
 
       AnnotatedDateTime[Zoned] :::
           [~Zoned] DateTime TimeZoneAnnotation? Annotations?
@@ -1518,6 +1505,18 @@ <h1>Static Semantics: IsValidDate ( ): a Boolean</h1>
 
     <emu-clause id="sec-temporal-iso8601grammar-static-semantics-early-errors">
       <h1>Static Semantics: Early Errors</h1>
+      <emu-grammar>
+        AnnotatedTime :::
+          TimeSpec DateTimeUTCOffset? TimeZoneAnnotation? Annotations?
+      </emu-grammar>
+      <ul>
+        <li>
+          It is a Syntax Error if IsValidMonthDay of ParseText(|TimeSpec| |DateTimeUTCOffset|, |DateSpecMonthDay|) is *true*.
+        </li>
+        <li>
+          It is a Syntax Error if ParseText(|TimeSpec| |DateTimeUTCOffset|, |DateSpecYearMonth|) is a Parse Node.
+        </li>
+      </ul>
       <emu-grammar>
         Date :::
           DateYear `-` DateMonth `-` DateDay