LibJS: Make parse_simplified_iso8601() use Optional<int> instead of -1

...for the non-success state. This fixes a crash when parsing dates with
the year -1, as we would assert successful parsing ("year != -1").
Mixing Optional and -1 seems worse and more complicated than just using
Optional for all the values, so I did that instead.

Userland/Libraries/LibJS/Runtime/DateConstructor.cpp

@@ -25,7 +25,7 @@ static Value parse_simplified_iso8601(const String& iso_8601)
     // Date.parse() is allowed to accept many formats. We strictly only accept things matching
     // 21.4.1.15 Date Time String Format, https://tc39.es/ecma262/#sec-date-time-string-format
     GenericLexer lexer(iso_8601);
-    auto lex_n_digits = [&](size_t n, int& out) {
+    auto lex_n_digits = [&](size_t n, Optional<int>& out) {
         if (lexer.tell_remaining() < n)
             return false;
         int r = 0;
@@ -39,36 +39,44 @@ static Value parse_simplified_iso8601(const String& iso_8601)
         return true;
     };
 
-    int year = -1, month = -1, day = -1;
-    int hours = -1, minutes = -1, seconds = -1, milliseconds = -1;
-    int timezone = -1;
-    int timezone_hours = -1, timezone_minutes = -1;
+    Optional<int> year;
+    Optional<int> month;
+    Optional<int> day;
+    Optional<int> hours;
+    Optional<int> minutes;
+    Optional<int> seconds;
+    Optional<int> milliseconds;
+    Optional<char> timezone;
+    Optional<int> timezone_hours;
+    Optional<int> timezone_minutes;
+
     auto lex_year = [&]() {
         if (lexer.consume_specific('+'))
             return lex_n_digits(6, year);
         if (lexer.consume_specific('-')) {
-            int absolute_year;
+            Optional<int> absolute_year;
             if (!lex_n_digits(6, absolute_year))
                 return false;
-            year = -absolute_year;
+            year = -absolute_year.value();
             return true;
         }
         return lex_n_digits(4, year);
     };
-    auto lex_month = [&]() { return lex_n_digits(2, month) && month >= 1 && month <= 12; };
-    auto lex_day = [&]() { return lex_n_digits(2, day) && day >= 1 && day <= 31; };
+    auto lex_month = [&]() { return lex_n_digits(2, month) && *month >= 1 && *month <= 12; };
+    auto lex_day = [&]() { return lex_n_digits(2, day) && *day >= 1 && *day <= 31; };
     auto lex_date = [&]() { return lex_year() && (!lexer.consume_specific('-') || (lex_month() && (!lexer.consume_specific('-') || lex_day()))); };
 
-    auto lex_hours_minutes = [&](int& out_h, int& out_m) {
-        int h, m;
-        if (lex_n_digits(2, h) && h >= 0 && h <= 24 && lexer.consume_specific(':') && lex_n_digits(2, m) && m >= 0 && m <= 59) {
-            out_h = h;
-            out_m = m;
+    auto lex_hours_minutes = [&](Optional<int>& out_h, Optional<int>& out_m) {
+        Optional<int> h;
+        Optional<int> m;
+        if (lex_n_digits(2, h) && *h >= 0 && *h <= 24 && lexer.consume_specific(':') && lex_n_digits(2, m) && *m >= 0 && *m <= 59) {
+            out_h = move(h);
+            out_m = move(m);
             return true;
         }
         return false;
     };
-    auto lex_seconds = [&]() { return lex_n_digits(2, seconds) && seconds >= 0 && seconds <= 59; };
+    auto lex_seconds = [&]() { return lex_n_digits(2, seconds) && *seconds >= 0 && *seconds <= 59; };
     auto lex_milliseconds = [&]() { return lex_n_digits(3, milliseconds); };
     auto lex_seconds_milliseconds = [&]() { return lex_seconds() && (!lexer.consume_specific('.') || lex_milliseconds()); };
     auto lex_timezone = [&]() {
@@ -90,34 +98,32 @@ static Value parse_simplified_iso8601(const String& iso_8601)
         return js_nan();
     }
 
-    // We parsed a valid date simplified ISO 8601 string. Values not present in the string are -1.
-    VERIFY(year != -1); // A valid date string always has at least a year.
+    // We parsed a valid date simplified ISO 8601 string.
+    VERIFY(year.has_value()); // A valid date string always has at least a year.
     struct tm tm = {};
-    tm.tm_year = year - 1900;
-    tm.tm_mon = month == -1 ? 0 : month - 1;
-    tm.tm_mday = day == -1 ? 1 : day;
-    tm.tm_hour = hours == -1 ? 0 : hours;
-    tm.tm_min = minutes == -1 ? 0 : minutes;
-    tm.tm_sec = seconds == -1 ? 0 : seconds;
+    tm.tm_year = *year - 1900;
+    tm.tm_mon = !month.has_value() ? 0 : *month - 1;
+    tm.tm_mday = day.value_or(1);
+    tm.tm_hour = hours.value_or(0);
+    tm.tm_min = minutes.value_or(0);
+    tm.tm_sec = seconds.value_or(0);
 
     // https://tc39.es/ecma262/#sec-date.parse:
     // "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."
     time_t timestamp;
-    if (timezone != -1 || hours == -1)
+    if (timezone.has_value() || !hours.has_value())
         timestamp = timegm(&tm);
     else
         timestamp = mktime(&tm);
 
     if (timezone == '-')
-        timestamp += (timezone_hours * 60 + timezone_minutes) * 60;
+        timestamp += (*timezone_hours * 60 + *timezone_minutes) * 60;
     else if (timezone == '+')
-        timestamp -= (timezone_hours * 60 + timezone_minutes) * 60;
+        timestamp -= (*timezone_hours * 60 + *timezone_minutes) * 60;
 
     // FIXME: reject timestamp if resulting value wouldn't fit in a double
 
-    if (milliseconds == -1)
-        milliseconds = 0;
-    return Value(1000.0 * timestamp + milliseconds);
+    return Value(1000.0 * timestamp + milliseconds.value_or(0));
 }
 
 DateConstructor::DateConstructor(GlobalObject& global_object)

Userland/Libraries/LibJS/Tests/builtins/Date/Date.parse.js

@@ -10,6 +10,7 @@ test("basic functionality", () => {
     expect(Date.parse("2020T23:59Z")).toBe(1577923140000);
 
     expect(Date.parse("+020000")).toBe(568971820800000);
+    expect(Date.parse("-000001")).toBe(-62198755200000);
     expect(Date.parse("+020000-01")).toBe(568971820800000);
     expect(Date.parse("+020000-01T00:00:00.000Z")).toBe(568971820800000);