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Fix #471 (#473)

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[JaEra] Calc: subtracting 1-year from date during Reiwa 1 yields unexpected results.
This commit is contained in:
Eric Wong 2019-04-24 13:37:49 -07:00 committed by GitHub
parent b03a026f6c
commit 1dee9dc984
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2 changed files with 86 additions and 0 deletions
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34
src/CalcViewModel/Common/DateCalculator.cpp
View File

@ -20,13 +20,27 @@ DateCalculationEngine::DateCalculationEngine(_In_ String^ calendarIdentifier)
// Returns: True if function succeeds to calculate the date else returns False
bool DateCalculationEngine::AddDuration(_In_ DateTime startDate, _In_ const DateDifference& duration, _Out_ DateTime *endDate)
{
auto currentCalendarSystem = m_calendar->GetCalendarSystem();
try
{
m_calendar->SetDateTime(startDate);
if (duration.year != 0)
{
// The Japanese Era system can have multiple year partitions within the same year.
// For example, April 30, 2019 is denoted April 30, Heisei 31; May 1, 2019 is denoted as May 1, Reiwa 1.
// The Calendar treats Heisei 31 and Reiwa 1 as separate years, which results in some unexpected behaviors where subtracting a year from Reiwa 1 results in a date in Heisei 31.
// To provide the expected result across era boundaries, we first convert the Japanese era system to a Gregorian system, do date math, and then convert back to the Japanese era system.
// This works because the Japanese era system maintains the same year/month boundaries and durations as the Gregorian system and is only different in display value.
if (currentCalendarSystem == CalendarIdentifiers::Japanese)
{
m_calendar->ChangeCalendarSystem(CalendarIdentifiers::Gregorian);
}
m_calendar->AddYears(duration.year);
m_calendar->ChangeCalendarSystem(currentCalendarSystem);
}
if (duration.month != 0)
{
@ -41,6 +55,9 @@ bool DateCalculationEngine::AddDuration(_In_ DateTime startDate, _In_ const Date
}
catch (Platform::InvalidArgumentException^ ex)
{
// ensure that we revert to the correct calendar system
m_calendar->ChangeCalendarSystem(currentCalendarSystem);
// Do nothing
return false;
}
@ -52,6 +69,8 @@ bool DateCalculationEngine::AddDuration(_In_ DateTime startDate, _In_ const Date
// Returns: True if function succeeds to calculate the date else returns False
bool DateCalculationEngine::SubtractDuration(_In_ DateTime startDate, _In_ const DateDifference& duration, _Out_ DateTime *endDate)
{
auto currentCalendarSystem = m_calendar->GetCalendarSystem();
// For Subtract the Algorithm is different than Add. Here the smaller units are subtracted first
// and then the larger units.
try
@ -68,13 +87,28 @@ bool DateCalculationEngine::SubtractDuration(_In_ DateTime startDate, _In_ const
}
if (duration.year != 0)
{
// The Japanese Era system can have multiple year partitions within the same year.
// For example, April 30, 2019 is denoted April 30, Heisei 31; May 1, 2019 is denoted as May 1, Reiwa 1.
// The Calendar treats Heisei 31 and Reiwa 1 as separate years, which results in some unexpected behaviors where subtracting a year from Reiwa 1 results in a date in Heisei 31.
// To provide the expected result across era boundaries, we first convert the Japanese era system to a Gregorian system, do date math, and then convert back to the Japanese era system.
// This works because the Japanese era system maintains the same year/month boundaries and durations as the Gregorian system and is only different in display value.
if (currentCalendarSystem == CalendarIdentifiers::Japanese)
{
m_calendar->ChangeCalendarSystem(CalendarIdentifiers::Gregorian);
}
m_calendar->AddYears(-duration.year);
m_calendar->ChangeCalendarSystem(currentCalendarSystem);
}
*endDate = m_calendar->GetDateTime();
}
catch (Platform::InvalidArgumentException^ ex)
{
// ensure that we revert to the correct calendar system
m_calendar->ChangeCalendarSystem(currentCalendarSystem);
// Do nothing
return false;
}

52
src/CalculatorUnitTests/DateCalculatorUnitTests.cpp
View File

@ -664,5 +664,57 @@ namespace DateCalculationUnitTests
VERIFY_IS_TRUE(actualValue.find(expectedValue) != wstring::npos, message.c_str());
}
}
TEST_METHOD(JaEraTransitionAddition)
{
auto viewModel = make_unique<DateCalculationEngine>(CalendarIdentifiers::Japanese);
auto cal = ref new Calendar();
// Showa period ended in Jan 1989.
cal->Year = 1989;
cal->Month = 1;
cal->Day = 1;
auto startTime = cal->GetDateTime();
cal->Year = 1990;
cal->Month = 1;
cal->Day = 1;
// Expect that adding a year across boundaries adds the equivalent in the Gregorian calendar.
auto expectedResult = cal->GetDateTime();
DateDifference duration;
duration.year = 1;
DateTime actualResult;
viewModel->AddDuration(startTime, duration, &actualResult);
VERIFY_ARE_EQUAL(expectedResult.UniversalTime, actualResult.UniversalTime);
}
TEST_METHOD(JaEraTransitionSubtraction)
{
auto viewModel = make_unique<DateCalculationEngine>(CalendarIdentifiers::Japanese);
auto cal = ref new Calendar();
// Showa period ended in Jan 1989.
cal->Year = 1990;
cal->Month = 1;
cal->Day = 1;
auto startTime = cal->GetDateTime();
cal->Year = 1989;
cal->Month = 1;
cal->Day = 1;
// Expect that adding a year across boundaries adds the equivalent in the Gregorian calendar.
auto expectedResult = cal->GetDateTime();
DateDifference duration;
duration.year = 1;
DateTime actualResult;
viewModel->SubtractDuration(startTime, duration, &actualResult);
VERIFY_ARE_EQUAL(expectedResult.UniversalTime, actualResult.UniversalTime);
}
};
}