Fix date() and time() function translation (#792)

[jamerst]

Fix #792 - date() function not being translated. Also fixes similar issue of time() function not being translated.

The comments previously implied that the Date and TimeOfDay properties of DateTime and DateTimeOffset were not supported by EF, but this is not the case with EF Core (see function mappings documentation).

The translation has been updated to use these properties for the functions so that they work correctly. Test cases have been added for when they are used in $orderby specifically.

Note that this issue was not present in most circumstances when the date() function was used in $filter due to the type conversion used when dealing with Date types in binary expressions resulting in dates being compared via an integer representation instead:

AspNetCoreOData/src/Microsoft.AspNetCore.OData/Query/Expressions/ExpressionBinderHelper.cs

Lines 425 to 441 in c860cdc

	private static Expression CreateDateBinaryExpression(Expression source, ODataQuerySettings querySettings)
	{
	source = ConvertToDateTimeRelatedConstExpression(source);
	// Year, Month, Day
	Expression year = GetProperty(source, ClrCanonicalFunctions.YearFunctionName, querySettings);
	Expression month = GetProperty(source, ClrCanonicalFunctions.MonthFunctionName, querySettings);
	Expression day = GetProperty(source, ClrCanonicalFunctions.DayFunctionName, querySettings);
	// return (year * 10000 + month * 100 + day)
	Expression result =
	Expression.Add(
	Expression.Add(Expression.Multiply(year, Expression.Constant(10000)),
	Expression.Multiply(month, Expression.Constant(100))), day);
	return CreateFunctionCallWithNullPropagation(result, new[] { source }, querySettings);
	}

This won't work with EF6 as it doesn't support translating the Date property. Not sure if this is a problem, does this library even officially support EF6? Attempting to work around it feels somewhat out of scope.

[jamerst]

@microsoft-github-policy-service agree

[WanjohiSammy]

Thanks for this fix.

Just to confirm..
Will this change break for users still using older versions of Entity Framework other than EF6? Why not add a condition to ensure it supports older versions of EF.

[WanjohiSammy]

Same here:
Older versions might not support new features from EF6. Adding a condition ensures compatibility.

[WanjohiSammy]

Same here:
https://github.com/OData/AspNetCoreOData/pull/1407/files#r1944232224

[jamerst]

Is it possible to tell if the query provider is EF6 from here?

The only place I can find that checks if it is EF6 is in TransformationBinderBase, and it uses the type of IQueryable.Provider to do so.

That would probably work for the translation in ExpressionBinderBase since TransformationBinderBase derives from it, but QueryBinder isn't exposed to the queryable at any point?

AspNetCoreOData/src/Microsoft.AspNetCore.OData/Query/Expressions/TransformationBinderBase.cs

Lines 49 to 54 in 40caec2

	internal virtual bool IsClassicEF(IQueryable query)
	{
	var providerNS = query.Provider.GetType().Namespace;
	return (providerNS == HandleNullPropagationOptionHelper.ObjectContextQueryProviderNamespaceEF6
	|| providerNS == HandleNullPropagationOptionHelper.EntityFrameworkQueryProviderNamespace);
	}

[WanjohiSammy]

Are you using EF here?