TryParse overload

[Atrejoe]

Added overload more similar to common TryParse implementations

[Atrejoe]

I implemented your suggestion of here: #11 (comment)

Instead of having to do:

bool IsCronExpressionValid(string expression) =>
    CrontabSchedule.TryParse(expression) != null;

one can now also call:

if(CrontabSchedule.TryParse(expression, var schedule))
    //Do something with the schedule

or for validation only

if (CrontabSchedule.TryParse(expression, var _))
    //your logic here

[Atrejoe]

I think the AppVeyor build failure may not be due to my commit.

[atifaziz]

I think the AppVeyor build failure may not be due to my commit.

Fixed with da31efd.

[rshillington]

Any chance of getting the PR merged?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.73%. Comparing base (dfea895) to head (034bec1).

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #54      +/-   ##
==========================================
- Coverage   88.37%   87.73%   -0.65%     
==========================================
  Files           5        5              
  Lines         430      432       +2     
  Branches        0       87      +87     
==========================================
- Hits          380      379       -1     
+ Misses         50       49       -1     
- Partials        0        4       +4     

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[Atrejoe]

I'm trying to get a necromancer badge: revived a nearly 5-year old PR just for kicks.

I still believe TryParse should return bool with a value out param though :)
https://learn.microsoft.com/en-us/dotnet/standard/design-guidelines/exceptions-and-performance#try-parse-pattern

[atifaziz]

I'm trying to get a necromancer badge: revived a nearly 5-year old PR just for kicks.

Right, let's try to get this, and boy, thanks for your patience. 😅

I've had an initial look and added my comments.

[atifaziz]

Formatting inconsistencies:

Suggested change

	public static bool TryParse(string expression, out CrontabSchedule? schedule)
	=> (schedule = TryParse(expression, null))!=null;
	public static bool TryParse(string expression, out CrontabSchedule? schedule) =>
	(schedule = TryParse(expression, null)) != null;

[atifaziz]

Formatting inconsistencies and options needs to be nullable to match the type of the argument of the overload being delegated to:

Suggested change

	public static bool TryParse(string expression, ParseOptions options, out CrontabSchedule? schedule)
	=> (schedule = TryParse(expression, options)) != null;
	public static bool TryParse(string expression, ParseOptions? options, out CrontabSchedule? schedule) =>
	(schedule = TryParse(expression, options)) != null;

[atifaziz]

The schedule parameter should be decorate with NotNullWhen(true) for correct nullability analysis.

You'll probably need to bring in PolySharp since NotNullWhenAttribute isn't defined for the frameworks that NCrontab targets. For .NET Framework 3.5, you may need conditional compilation too.

[atifaziz]

For consistency with the rest of the tests, use Assert.That:

Suggested change

	Assert.False(CrontabSchedule.TryParse(string.Empty, out var _));
	Assert.That(CrontabSchedule.TryParse(string.Empty, out var result), Is.False);
	Assert.That(result, Is.Null);

Also, checking that result is indeed null would be more thorough.

[atifaziz]

A few things:

• The first argument to TryParse here should be null, not string.Empty.
• For consistency with the rest of the tests, use Assert.That.
• Testing that result is indeed null would be more thorough.

Suggested change

	Assert.False(CrontabSchedule.TryParse(string.Empty, out var _));
	Assert.That(CrontabSchedule.TryParse(null!, out var result), Is.False);
	Assert.That(result, Is.Null);

[atifaziz]

For consistency with the rest of the tests, use Assert.That:

Suggested change

	Assert.False(CrontabSchedule.TryParse(expression, new ParseOptions
	{
	IncludingSeconds = includingSeconds
	}, out var _));
	Assert.That(CrontabSchedule.TryParse(expression, new ParseOptions
	{
	IncludingSeconds = includingSeconds
	}, out _), Is.False);