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Merged
merged 3 commits into from
Sep 28, 2025
Merged

Fallback to using DateTimeOffset.TryParse if normal parsing doesn't work #118

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ee0c328
Fallback to using DateTimeOffset.TryParse if normal parsing doesn't work
ejsmith Sep 28, 2025
4e312da
Use shared regex
ejsmith Sep 28, 2025
dc02960
Refactor method
ejsmith Sep 28, 2025
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60 changes: 57 additions & 3 deletions src/Exceptionless.DateTimeExtensions/DateMath.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,9 @@ public static class DateMath
// Pre-compiled regex for operation parsing to avoid repeated compilation
private static readonly Regex _operationRegex = new(@"([+\-/])(\d*)([yMwdhHms])", RegexOptions.Compiled);

// Pre-compiled regex for offset parsing to avoid repeated compilation
private static readonly Regex _offsetRegex = new(@"(Z|[+-]\d{2}:\d{2})$", RegexOptions.Compiled);

/// <summary>
/// Parses a date math expression and returns the resulting DateTimeOffset.
/// </summary>
Expand Down Expand Up @@ -64,7 +67,9 @@ public static bool TryParse(string expression, DateTimeOffset relativeBaseTime,

var match = Parser.Match(expression);
if (!match.Success)
return false;
{
return TryParseFallbackDate(expression, relativeBaseTime.Offset, isUpperLimit, out result);
}

return TryParseFromMatch(match, relativeBaseTime, isUpperLimit, out result);
}
Expand Down Expand Up @@ -110,7 +115,9 @@ public static bool TryParse(string expression, TimeZoneInfo timeZone, bool isUpp

var match = Parser.Match(expression);
if (!match.Success)
return false;
{
return TryParseFallbackDate(expression, timeZone, isUpperLimit, out result);
}

return TryParseFromMatch(match, timeZone, isUpperLimit, out result);
}
Expand Down Expand Up @@ -211,7 +218,54 @@ public static bool IsValidExpression(string expression)
if (String.IsNullOrEmpty(expression))
return false;

return Parser.IsMatch(expression);
if (Parser.IsMatch(expression))
return true;

// Fallback: Check if it's a valid explicit date
return TryParseFallbackDate(expression, TimeZoneInfo.Local, false, out _);
}

private static bool TryParseFallbackDate(string expression, TimeZoneInfo defaultTimeZone, bool isUpperLimit, out DateTimeOffset result)
{
return TryParseFallbackDateCore(expression, isUpperLimit, out result, defaultTimeZone.GetUtcOffset);
}

private static bool TryParseFallbackDate(string expression, TimeSpan offset, bool isUpperLimit, out DateTimeOffset result)
{
return TryParseFallbackDateCore(expression, isUpperLimit, out result, _ => offset);
}

private static bool TryParseFallbackDateCore(string expression, bool isUpperLimit, out DateTimeOffset result, Func<DateTime, TimeSpan> offsetResolver)
{
result = default;

if (_offsetRegex.IsMatch(expression) && DateTimeOffset.TryParse(expression, out DateTimeOffset explicitDate))
{
result = explicitDate;

if (result.TimeOfDay == TimeSpan.Zero && isUpperLimit)
{
// If time is exactly midnight, and it's an upper limit, set to end of day
result = result.EndOfDay();
}

return true;
}

if (DateTime.TryParse(expression, out DateTime dt))
{
result = new DateTimeOffset(dt, offsetResolver(dt));

if (result.TimeOfDay == TimeSpan.Zero && isUpperLimit)
{
// If time is exactly midnight, and it's an upper limit, set to end of day
result = result.EndOfDay();
}

return true;
}

return false;
}

/// <summary>
Expand Down
67 changes: 63 additions & 4 deletions tests/Exceptionless.DateTimeExtensions.Tests/DateMathTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -311,7 +311,6 @@ public void Parse_ExplicitDateWithOperations_ReturnsCorrectResult(string express
[InlineData(" ")]
[InlineData("invalid")]
[InlineData("now+1x")] // Invalid unit
[InlineData("2023-01-01")] // Missing ||
[InlineData("||+1d")] // Missing anchor
[InlineData("now/x")] // Invalid rounding unit
[InlineData("2023-13-01||")] // Invalid month
Expand Down Expand Up @@ -344,6 +343,7 @@ public void Parse_NullExpression_ThrowsArgumentException()
[InlineData("now")]
[InlineData("now+1h")]
[InlineData("now-1d/d")]
[InlineData("2023-06-15")]
[InlineData("2023-06-15||")]
[InlineData("2023-06-15||+1M/d")]
[InlineData("2025-01-01T01:25:35Z||+3d/d")]
Expand All @@ -368,7 +368,6 @@ public void TryParse_ValidExpressions_ReturnsTrueAndCorrectResult(string express
[InlineData("")]
[InlineData("invalid")]
[InlineData("now+")]
[InlineData("2023-01-01")] // Missing ||
[InlineData("||+1d")] // Missing anchor
[InlineData("2001.02.01||")] // Dotted format no longer supported
[InlineData("now/d+1h")] // Rounding must be final operation
Expand Down Expand Up @@ -398,9 +397,69 @@ public void TryParse_NullExpression_ReturnsFalse()
Assert.Equal(default, result);
}

[Fact]
public void TryParse_FallbackExplicitDate_AppliesBaseOffset()
{
const string expression = "2023-04-01";
_logger.LogDebug("Testing TryParse fallback with expression: '{Expression}', BaseTime: {BaseTime}", expression, _baseTime);

bool success = DateMath.TryParse(expression, _baseTime, false, out var result);

_logger.LogDebug("TryParse success: {Success}, Result: {Result}", success, result);

Assert.True(success);
var expected = new DateTimeOffset(2023, 4, 1, 0, 0, 0, _baseTime.Offset);
Assert.Equal(expected, result);
}

[Fact]
public void TryParse_FallbackExplicitDateUpperLimit_AdjustsToEndOfDay()
{
const string expression = "2023-07-10";
_logger.LogDebug("Testing TryParse fallback upper limit with expression: '{Expression}', BaseTime: {BaseTime}", expression, _baseTime);

bool success = DateMath.TryParse(expression, _baseTime, true, out var result);

_logger.LogDebug("TryParse success: {Success}, Result: {Result}", success, result);

Assert.True(success);
var expected = new DateTimeOffset(2023, 7, 10, 23, 59, 59, 999, _baseTime.Offset);
Assert.Equal(expected, result);
}

[Fact]
public void TryParse_FallbackExplicitDateWithTimezone_PreservesOffset()
{
const string expression = "2023-05-05T18:45:00-07:00";
_logger.LogDebug("Testing TryParse fallback with explicit offset expression: '{Expression}'", expression);

bool success = DateMath.TryParse(expression, _baseTime, false, out var result);

_logger.LogDebug("TryParse success: {Success}, Result: {Result}", success, result);

Assert.True(success);
Assert.Equal(new DateTimeOffset(2023, 5, 5, 18, 45, 0, TimeSpan.FromHours(-7)), result);
}

[Fact]
public void TryParse_FallbackExplicitDateWithTimeZoneInfo_UsesProvidedOffset()
{
const string expression = "2023-09-15";
var customZone = TimeZoneInfo.CreateCustomTimeZone("TestPlusThree", TimeSpan.FromHours(3), "Test +3", "Test +3");
_logger.LogDebug("Testing TryParse fallback with TimeZoneInfo: '{Expression}', TimeZone: {TimeZone}", expression, customZone);

bool success = DateMath.TryParse(expression, customZone, false, out var result);

_logger.LogDebug("TryParse success: {Success}, Result: {Result}", success, result);

Assert.True(success);
Assert.Equal(new DateTimeOffset(2023, 9, 15, 0, 0, 0, customZone.BaseUtcOffset), result);
}

[Theory]
[InlineData("now+1h", false)]
[InlineData("now-1d/d", true)]
[InlineData("2023-06-15", false)]
[InlineData("2023-06-15||+1M", false)]
[InlineData("2025-01-01T01:25:35Z||+3d/d", true)]
public void Parse_And_TryParse_ReturnSameResults(string expression, bool isUpperLimit)
Expand Down Expand Up @@ -556,7 +615,7 @@ public void ParseTimeZone_Now_ReturnsCorrectTimezone(string timeZoneId, int expe
public void ParseTimeZone_ExplicitDateWithoutTimezone_UsesSpecifiedTimezone()
{
var easternTimeZone = TimeZoneInfo.FindSystemTimeZoneById("US/Eastern");
const string expression = "2023-06-15T14:30:00||";
const string expression = "2023-06-15T14:30:00";

_logger.LogDebug("Testing Parse with TimeZoneInfo for expression: '{Expression}', TimeZone: {TimeZone}",
expression, easternTimeZone.Id);
Expand All @@ -581,7 +640,7 @@ public void ParseTimeZone_ExplicitDateWithoutTimezone_UsesSpecifiedTimezone()
public void ParseTimeZone_ExplicitDateWithTimezone_PreservesOriginalTimezone()
{
var pacificTimeZone = TimeZoneInfo.FindSystemTimeZoneById("US/Pacific");
const string expression = "2023-06-15T14:30:00+05:00||"; // Explicit +05:00 timezone
const string expression = "2023-06-15T14:30:00+05:00"; // Explicit +05:00 timezone

_logger.LogDebug("Testing Parse with TimeZoneInfo for expression: '{Expression}', TimeZone: {TimeZone}",
expression, pacificTimeZone.Id);
Expand Down