More robust handling of DateTime parsing with daylight savings-type transitions, particularly when they occur at midnight (e.g. Brazil)
Retrying from 173286563 which had to be rolled back.
Cloned from CL 173286563 by 'g4 patch'.
Original change by alanknight@alanknight:dst:1458:citc on 2017/10/24 11:32:32.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=174055235
diff --git a/lib/src/intl/date_format.dart b/lib/src/intl/date_format.dart
index e9def84..a1fc6fb 100644
--- a/lib/src/intl/date_format.dart
+++ b/lib/src/intl/date_format.dart
@@ -324,6 +324,7 @@
// values with no delimiters, which we currently don't do. Should we?
var dateFields = new _DateBuilder();
if (utc) dateFields.utc = true;
+ dateFields._dateOnly = this.dateOnly;
var stream = new _Stream(inputString);
_formatFields.forEach((f) => f.parse(stream, dateFields));
if (strict && !stream.atEnd()) {
@@ -334,6 +335,13 @@
return dateFields.asDate();
}
+ /// Does our format only only date fields, and no time fields.
+ ///
+ /// For example, 'yyyy-MM-dd' would be true, but 'dd hh:mm' would be false.
+ bool get dateOnly => _dateOnly ??= _checkDateOnly;
+ bool _dateOnly;
+ bool get _checkDateOnly => _formatFields.every((each) => each.forDate);
+
/// Given user input, attempt to parse the [inputString] into the anticipated
/// format, treating it as being in UTC.
///
diff --git a/lib/src/intl/date_format_field.dart b/lib/src/intl/date_format_field.dart
index 495f8f9..8a5d25e 100644
--- a/lib/src/intl/date_format_field.dart
+++ b/lib/src/intl/date_format_field.dart
@@ -22,6 +22,10 @@
_trimmedPattern = pattern.trim();
}
+ /// Does this field potentially represent part of a Date, i.e. is not
+ /// time-specific.
+ bool get forDate => true;
+
/// Return the width of [pattern]. Different widths represent different
/// formatting options. See the comment for DateFormat for details.
int get width => pattern.length;
@@ -253,6 +257,17 @@
new _LoosePatternField(pattern, parent).parse(input, dateFields);
}
+ bool _forDate;
+
+ /// Is this field involved in computing the date portion, as opposed to the
+ /// time.
+ ///
+ /// The [pattern] will contain one or more of a particular format character,
+ /// e.g. "yyyy" for a four-digit year. This hard-codes all the pattern
+ /// characters that pertain to dates. The remaining characters, 'ahHkKms' are
+ /// all time-related. See e.g. [formatField]
+ bool get forDate => _forDate ??= 'cdDEGLMQvyZz'.contains(pattern[0]);
+
/// Parse a field representing part of a date pattern. Note that we do not
/// return a value, but rather build up the result in [builder].
void parseField(_Stream input, _DateBuilder builder) {
@@ -578,27 +593,8 @@
return padTo(width, date.day);
}
- String formatDayOfYear(DateTime date) => padTo(width, dayNumberInYear(date));
-
- /// Return the ordinal day, i.e. the day number in the year.
- int dayNumberInYear(DateTime date) {
- if (date.month == 1) return date.day;
- if (date.month == 2) return date.day + 31;
- return ordinalDayFromMarchFirst(date) + 59 + (isLeapYear(date) ? 1 : 0);
- }
-
- /// Return the day of the year counting March 1st as 1, after which the
- /// number of days per month is constant, so it's easier to calculate.
- /// Formula from http://en.wikipedia.org/wiki/Ordinal_date
- int ordinalDayFromMarchFirst(DateTime date) =>
- ((30.6 * date.month) - 91.4).floor() + date.day;
-
- /// Return true if this is a leap year. Rely on [DateTime] to do the
- /// underlying calculation, even though it doesn't expose the test to us.
- bool isLeapYear(DateTime date) {
- var feb29 = new DateTime(date.year, 2, 29);
- return feb29.month == 2;
- }
+ String formatDayOfYear(DateTime date) =>
+ padTo(width, _dayOfYear(date.month, date.day, _isLeapYear(date)));
String formatDayOfWeek(DateTime date) {
// Note that Dart's weekday returns 1 for Monday and 7 for Sunday.
diff --git a/lib/src/intl/date_format_helpers.dart b/lib/src/intl/date_format_helpers.dart
index 3ad651d..327714c 100644
--- a/lib/src/intl/date_format_helpers.dart
+++ b/lib/src/intl/date_format_helpers.dart
@@ -4,6 +4,31 @@
part of intl;
+/// Given a month and day number, return the day of the year, all one-based.
+///
+/// For example,
+/// * January 2nd (1, 2) -> 2.
+/// * February 5th (2, 5) -> 36.
+/// * March 1st of a non-leap year (3, 1) -> 60.
+int _dayOfYear(int month, int day, bool leapYear) {
+ if (month == 1) return day;
+ if (month == 2) return day + 31;
+ return ordinalDayFromMarchFirst(month, day) + 59 + (leapYear ? 1 : 0);
+}
+
+/// Return true if this is a leap year. Rely on [DateTime] to do the
+/// underlying calculation, even though it doesn't expose the test to us.
+bool _isLeapYear(DateTime date) {
+ var feb29 = new DateTime(date.year, 2, 29);
+ return feb29.month == 2;
+}
+
+/// Return the day of the year counting March 1st as 1, after which the
+/// number of days per month is constant, so it's easier to calculate.
+/// Formula from http://en.wikipedia.org/wiki/Ordinal_date
+int ordinalDayFromMarchFirst(int month, int day) =>
+ ((30.6 * month) - 91.4).floor() + day;
+
/// A class for holding onto the data for a date so that it can be built
/// up incrementally.
class _DateBuilder {
@@ -19,6 +44,18 @@
bool pm = false;
bool utc = false;
+ /// Is this constructing a pure date.
+ ///
+ /// This is important because some locales change times at midnight,
+ /// e.g. Brazil. So if we try to create a DateTime representing a date at
+ /// midnight on the day of transition it will jump forward or back 1 hour. If
+ /// it jumps forward that's mostly harmless if we only care about the
+ /// date. But if it jumps backwards that will change the date, which is
+ /// bad. Compensate by adjusting the time portion forward. But only do that
+ /// when we're explicitly trying to construct a date, which we can tell from
+ /// the format.
+ bool _dateOnly = false;
+
// Functions that exist just to be closurized so we can pass them to a general
// method.
void setYear(x) {
@@ -67,7 +104,16 @@
// which will catch cases like "14:00:00 PM".
var date = asDate();
_verify(hour24, date.hour, date.hour, "hour", s, date);
- _verify(day, date.day, date.day, "day", s, date);
+ if (day > 31) {
+ // We have an ordinal date, compute the corresponding date for the result
+ // and compare to that.
+ var leapYear = _isLeapYear(date);
+ var correspondingDay = _dayOfYear(date.month, date.day, leapYear);
+ _verify(day, correspondingDay, correspondingDay, "day", s, date);
+ } else {
+ // We have the day of the month, compare directly.
+ _verify(day, date.day, date.day, "day", s, date);
+ }
_verify(year, date.year, date.year, "year", s, date);
}
@@ -83,23 +129,61 @@
/// Return a date built using our values. If no date portion is set,
/// use the "Epoch" of January 1, 1970.
- DateTime asDate({int retries: 10}) {
+ DateTime asDate({int retries: 3}) {
// TODO(alanknight): Validate the date, especially for things which
// can crash the VM, e.g. large month values.
- var result;
if (utc) {
- result = new DateTime.utc(
+ return new DateTime.utc(
year, month, day, hour24, minute, second, fractionalSecond);
} else {
- result = new DateTime(
+ var preliminaryResult = new DateTime(
year, month, day, hour24, minute, second, fractionalSecond);
- // TODO(alanknight): Issue 15560 means non-UTC dates occasionally come out
- // in UTC, or, alternatively, are constructed as if in UTC and then have
- // the offset subtracted. If that happens, retry, several times if
- // necessary.
- if (retries > 0 && (result.hour != hour24 || result.day != day)) {
- result = asDate(retries: retries - 1);
- }
+ return _correctForErrors(preliminaryResult, retries);
+ }
+ }
+
+ static final Duration _zeroDuration = new Duration();
+
+ /// Given a local DateTime, check for errors and try to compensate for them if
+ /// possible.
+ DateTime _correctForErrors(DateTime result, int retries) {
+ // There are 3 kinds of errors that we know of
+ //
+ // 1 - Issue 15560, sometimes we get UTC even when we asked for local, or
+ // they get constructed as if in UTC and then have the offset
+ // subtracted. Retry, possibly several times, until we get something that
+ // looks valid, or we give up.
+ //
+ // 2 - Timezone transitions. If we ask for the time during a timezone
+ // transition then it will offset it by that transition. This is
+ // particularly a problem if the timezone transition happens at midnight,
+ // and we're looking for a date with no time component. This happens in
+ // Brazil, and we can end up with 11:00pm the previous day. Add time to
+ // compensate.
+ //
+ // 3 - Invalid input which the constructor nevertheless accepts. Just
+ // return what it created, and verify will catch it if we're in strict
+ // mode.
+ var leapYear = _isLeapYear(result);
+ var correspondingDay = _dayOfYear(result.month, result.day, leapYear);
+
+ if (result.isUtc &&
+ (result.hour != hour24 || result.day != correspondingDay)) {
+ // This may be a UTC failure. Retry and if the result doesn't look
+ // like it's in the UTC time zone, use that instead.
+ var retry = asDate(retries: retries - 1);
+ if (retry.timeZoneOffset != _zeroDuration) return retry;
+ }
+ if (_dateOnly && day != correspondingDay) {
+ // If we're _dateOnly, then hours should be zero, but might have been
+ // offset to e.g. 11:00pm the previous day. Add that time back in. We
+ // only care about jumps backwards. If we were offset to e.g. 1:00am the
+ // same day that's all right for a date. It gets the day correct, and we
+ // have no way to even represent midnight on a day when it doesn't
+ // happen.
+ var adjusted = result.add(new Duration(hours: (24 - result.hour)));
+ if (_dayOfYear(adjusted.month, adjusted.day, leapYear) == day)
+ return adjusted;
}
return result;
}
diff --git a/test/brazil_timezone_test.dart b/test/brazil_timezone_test.dart
new file mode 100644
index 0000000..8bdcc03
--- /dev/null
+++ b/test/brazil_timezone_test.dart
@@ -0,0 +1,23 @@
+// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Test date formatting and parsing while the system time zone is set to
+/// America/Sao Paulo.
+///
+/// In Brazil the time change spring/fall happens at midnight. This can make
+/// operations working with dates as midnight on a particular day fail. For
+/// example, in the (Brazilian) autumn, a date might "fall back" an hour and be
+/// on the previous day. This test verifies that we're handling those
+/// situations.
+
+// This test relies on setting the TZ environment variable to affect the
+// system's time zone calculations. That's only effective on Linux environments,
+// and would only work in a browser if we were able to set it before the browser
+// launched, which we aren't. So restrict this test to the VM and Linux.
+import 'timezone_test_core.dart';
+
+main() {
+ // The test date is Jan 1, so Brazilian Summer Time will be in effect.
+ testTimezone('America/Sao_Paulo', expectedUtcOffset: -2);
+}
diff --git a/test/date_time_format_test_core.dart b/test/date_time_format_test_core.dart
index c1a4dc0..e6f88f5 100644
--- a/test/date_time_format_test_core.dart
+++ b/test/date_time_format_test_core.dart
@@ -160,7 +160,7 @@
var format = new DateFormat(skeleton, localeName);
if (forceAscii) format.useNativeDigits = false;
var actualResult = format.format(date);
- var parsed = format.parse(actualResult);
+ var parsed = format.parseStrict(actualResult);
var thenPrintAgain = format.format(parsed);
expect(thenPrintAgain, equals(actualResult));
}
@@ -399,7 +399,11 @@
Map<int, DateTime> generateDates(int year, int leapDay) =>
new Iterable.generate(365 + leapDay, (n) => n + 1)
.map((day) {
- var result = new DateTime(year, 1, day);
+ // Typically a "date" would have a time value of zero, but we
+ // give them an hour value, because they can get created with an
+ // offset to the previous day in time zones where the daylight
+ // savings transition happens at midnight (e.g. Brazil).
+ var result = new DateTime(year, 1, day, 3);
// TODO(alanknight): This is a workaround for dartbug.com/15560.
if (result.toUtc() == result) result = new DateTime(year, 1, day);
return result;
@@ -415,7 +419,12 @@
expect(formatted, (number + 1).toString());
var formattedWithYear = withYear.format(date);
var parsed = withYear.parse(formattedWithYear);
- expect(parsed, date);
+ // Only compare the date portion, because time zone changes (e.g. DST) can
+ // cause the hour values to be different.
+ expect(parsed.year, date.year);
+ expect(parsed.month, date.month);
+ expect(parsed.day, date.day,
+ reason: 'Mismatch between parsed ($parsed) and original ($date)');
});
}
diff --git a/test/england_timezone_test.dart b/test/england_timezone_test.dart
new file mode 100644
index 0000000..a0e3630
--- /dev/null
+++ b/test/england_timezone_test.dart
@@ -0,0 +1,14 @@
+// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Test date formatting and parsing while the system time zone is set to
+/// Europe/London.
+///
+/// This is the same as UTC for part of the year, which makes it an interesting
+/// edge case.
+import 'timezone_test_core.dart';
+
+main() {
+ testTimezone('Europe/London', expectedUtcOffset: 0);
+}
diff --git a/test/scorbeysund_timezone_test.dart b/test/scorbeysund_timezone_test.dart
new file mode 100644
index 0000000..a5a9b48
--- /dev/null
+++ b/test/scorbeysund_timezone_test.dart
@@ -0,0 +1,14 @@
+// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Test date formatting and parsing while the system time zone is set to
+/// America/Scoresbysund.
+///
+/// This is the same as UTC for part of the year and -1:00 from UTC otherwise,
+/// which makes it an interesting edge case.
+import 'timezone_test_core.dart';
+
+main() {
+ testTimezone('America/Scoresbysund', expectedUtcOffset: -1);
+}
diff --git a/test/timezone_local_even_test_helper.dart b/test/timezone_local_even_test_helper.dart
new file mode 100644
index 0000000..cd06423
--- /dev/null
+++ b/test/timezone_local_even_test_helper.dart
@@ -0,0 +1,31 @@
+// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Test date formatting and parsing using locale data directly imported.
+///
+/// This is a copy of date_time_format_local_even_test.dart which also
+/// verifies the time zone against an environment variable.
+
+import 'dart:io';
+
+import 'date_time_format_test_stub.dart';
+import 'package:intl/date_symbol_data_local.dart';
+import 'package:test/test.dart';
+
+main() {
+ var tzOffset = Platform.environment['EXPECTED_TZ_OFFSET_FOR_TEST'];
+ var timezoneName = Platform.environment['TZ'];
+ if (tzOffset != null) {
+ test("Actually running in the correct time zone: $timezoneName", () {
+ // Pick a constant Date so that the offset is known.
+ var d = new DateTime(2012, 1, 1, 7, 6, 5);
+ print("Time zone offset is ${d.timeZoneOffset.inHours}");
+ print("Time zone name is ${d.timeZoneName}");
+ expect(tzOffset, '${d.timeZoneOffset.inHours}');
+ });
+ }
+
+ // Run the main date formatting tests with a large set of locales.
+ runWith(evenLocales, null, initializeDateFormatting);
+}
diff --git a/test/timezone_test_core.dart b/test/timezone_test_core.dart
new file mode 100644
index 0000000..435f2a7
--- /dev/null
+++ b/test/timezone_test_core.dart
@@ -0,0 +1,57 @@
+// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Test date formatting and parsing while the system time zone is set.
+import 'package:test/test.dart';
+import 'dart:io';
+import 'dart:convert';
+
+// This test relies on setting the TZ environment variable to affect the
+// system's time zone calculations. That's only effective on Linux environments,
+// and would only work in a browser if we were able to set it before the browser
+// launched, which we aren't. So restrict this test to the VM and Linux.
+@TestOn('vm')
+@TestOn('linux')
+
+/// The VM arguments we were given, most importantly package-root.
+final vmArgs = Platform.executableArguments;
+
+final dart = Platform.executable;
+
+/// Test for a particular timezone. In order to verify that we are in fact
+/// running in that time zone, verify that the DateTime offset is one of the
+/// expected values.
+testTimezone(String timezoneName, {int expectedUtcOffset}) {
+ // The VM can be invoked with a "-DPACKAGE_DIR=<directory>" argument to
+ // indicate the root of the Intl package. If it is not provided, we assume
+ // that the root of the Intl package is the current directory.
+ var packageDir = new String.fromEnvironment('PACKAGE_DIR');
+ var packageRelative = 'test/timezone_local_even_test_helper.dart';
+ var fileToSpawn =
+ packageDir == null ? packageRelative : '$packageDir/$packageRelative';
+
+ test("Run tests in $timezoneName time zone", () async {
+ List<String> args = []
+ ..addAll(vmArgs)
+ ..add(fileToSpawn);
+ var environment = <String, String>{'TZ': timezoneName};
+ if (expectedUtcOffset != null) {
+ environment['EXPECTED_TZ_OFFSET_FOR_TEST'] = '$expectedUtcOffset';
+ }
+ var result = await Process.run(dart, args,
+ stdoutEncoding: UTF8,
+ stderrEncoding: UTF8,
+ includeParentEnvironment: true,
+ environment: environment);
+ // Because the actual tests are run in a spawned parocess their output isn't
+ // directly visible here. To debug, it's necessary to look at the output of
+ // that test, so we print it here for convenience.
+ print("Spawning test to run in the $timezoneName time zone. Stderr is:");
+ print(result.stderr);
+ print("Spawned test in $timezoneName time zone has Stdout:");
+ print(result.stdout);
+ expect(result.exitCode, 0,
+ reason: "Spawned test failed. See the test log from stderr to debug");
+ });
+}
diff --git a/test/utc_timezone_test.dart b/test/utc_timezone_test.dart
new file mode 100644
index 0000000..0ef5240
--- /dev/null
+++ b/test/utc_timezone_test.dart
@@ -0,0 +1,11 @@
+// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Test date formatting and parsing while the system time zone is set to
+/// UTC.
+import 'timezone_test_core.dart';
+
+main() {
+ testTimezone('UTC', expectedUtcOffset: 0);
+}
