Allow parsing of legacy dates without time-zone offset as being in local time.

Author: iamstolis

graal-js/src/com.oracle.truffle.js.parser/src/com/oracle/truffle/js/parser/date/DateParser.java

@@ -50,6 +50,7 @@
 import java.util.HashMap;
 import java.util.Locale;
 
+import com.oracle.truffle.js.runtime.JSContext;
 import com.oracle.truffle.js.runtime.JSRealm;
 
 // @formatter:off
@@ -679,7 +680,8 @@ private boolean patchResult(final boolean strict) {
         if (isSet(HOUR) && !isSet(MINUTE)) {
             return false;
         }
-        if (realm.getContext().isOptionV8CompatibilityMode()) {
+        JSContext context = realm.getContext();
+        if (context.isOptionV8CompatibilityMode()) {
             if (!isSet(YEAR) && !isSet(DAY) && !isSet(MONTH)) {
                 return false;
             }
@@ -688,7 +690,7 @@ private boolean patchResult(final boolean strict) {
         // fill in default values for unset fields except timezone
         for (int field = YEAR; field <= TIMEZONE; field++) {
             if (get(field) == null) {
-                if (field == TIMEZONE && !dateOnly) {
+                if (field == TIMEZONE && !isUTCDefaultTimezone(context, dateOnly, strict)) {
                     // When the UTC offset representation is absent,
                     // date-only forms are interpreted as a UTC time and
                     // date-time forms are interpreted as a local time (= empty TIMEZONE).
@@ -737,6 +739,10 @@ private boolean patchResult(final boolean strict) {
         return true;
     }
 
+    private static boolean isUTCDefaultTimezone(JSContext context, boolean dateOnly, boolean strict) {
+        return (strict || context.getContextOptions().shouldUseUTCForLegacyDates()) && dateOnly;
+    }
+
     private static void addName(final String str, final int type, final int value) {
         final Name name = new Name(str, type, value);
         names.put(name.key, name);

graal-js/src/com.oracle.truffle.js/src/com/oracle/truffle/js/runtime/JSContextOptions.java

@@ -487,6 +487,11 @@ public Map<String, String> apply(String value) {
     protected static final OptionKey<Boolean> TOP_LEVEL_AWAIT = new OptionKey<>(false);
     @CompilationFinal private boolean topLevelAwait;
 
+    public static final String USE_UTC_FOR_LEGACY_DATES_NAME = JS_OPTION_PREFIX + "use-utc-for-legacy-dates";
+    @Option(name = USE_UTC_FOR_LEGACY_DATES_NAME, category = OptionCategory.EXPERT, stability = OptionStability.STABLE, help = "Determines what time zone (UTC or local time zone) should be used when UTC offset is absent in a parsed date.") //
+    public static final OptionKey<Boolean> USE_UTC_FOR_LEGACY_DATES = new OptionKey<>(true);
+    @CompilationFinal private boolean useUTCForLegacyDates;
+
     JSContextOptions(JSParserOptions parserOptions, OptionValues optionValues) {
         this.parserOptions = parserOptions;
         this.optionValues = optionValues;
@@ -571,6 +576,7 @@ private void cacheOptions() {
         this.maxPrototypeChainLength = readIntegerOption(MAX_PROTOTYPE_CHAIN_LENGTH);
         this.asyncStackTraces = readBooleanOption(ASYNC_STACK_TRACES);
         this.topLevelAwait = TOP_LEVEL_AWAIT.hasBeenSet(optionValues) ? readBooleanOption(TOP_LEVEL_AWAIT) : getEcmaScriptVersion() >= JSConfig.ECMAScript2022;
+        this.useUTCForLegacyDates = USE_UTC_FOR_LEGACY_DATES.hasBeenSet(optionValues) ? readBooleanOption(USE_UTC_FOR_LEGACY_DATES) : !v8CompatibilityMode;
 
         this.propertyCacheLimit = readIntegerOption(PROPERTY_CACHE_LIMIT);
         this.functionCacheLimit = readIntegerOption(FUNCTION_CACHE_LIMIT);
@@ -925,6 +931,10 @@ public boolean isAsyncStackTraces() {
         return asyncStackTraces;
     }
 
+    public boolean shouldUseUTCForLegacyDates() {
+        return useUTCForLegacyDates;
+    }
+
     @Override
     public int hashCode() {
         int hash = 5;
@@ -973,6 +983,7 @@ public int hashCode() {
         hash = 53 * hash + this.propertyCacheLimit;
         hash = 53 * hash + this.functionCacheLimit;
         hash = 53 * hash + (this.topLevelAwait ? 1 : 0);
+        hash = 53 * hash + (this.useUTCForLegacyDates ? 1 : 0);
         return hash;
     }
 
@@ -1120,6 +1131,9 @@ public boolean equals(Object obj) {
         if (this.topLevelAwait != other.topLevelAwait) {
             return false;
         }
+        if (this.useUTCForLegacyDates != other.useUTCForLegacyDates) {
+            return false;
+        }
         return Objects.equals(this.parserOptions, other.parserOptions);
     }
 }