Cannot ignore source null values, if destination property is not nullable

[utillity]

I use AutoMapper to ensure all properties are accounted for between Request, Database, and DTO (outgoing data-transfer-objects).

I have request objects coming via the API, to patch an object in the Database.

	[Fact]
	public void MapRequestToRecord()
	{
		var configuration = new MapperConfiguration(cfg =>
		{
			cfg.AllowNullDestinationValues = true;
			cfg.CreateMap<SomeRequest, SomeRecord>()
				// cannot access property-info here to check for nullability
				.ForAllMembers(opt => opt.Condition((s, t, srcV, destV, ctx) => srcV != null));
		});
		configuration.AssertConfigurationIsValid();
		var mapper = configuration.CreateMapper();

		mapper.Map<SomeRecord>(new SomeRequest()).Count.Should().Be(2);
		mapper.Map<SomeRecord>(new SomeRequest { Count = 3 }).Count.Should().Be(3);
	}

	private class SomeRequest
	{
		public int? Count { get; set; }
	}

	private class SomeRecord
	{
		public int Count { get; set; } = 2;
	}

The srcV is converted to 0, which is understandable. But in the Condition method I would like to know which property I'm on (PropertyInfo), so I can at least use reflection to check if the original source-value was null.

Is it possible to add this (either as param or to the ResolutionContext)?

BTW: tested with AutoMapper 14.0.0

[lbargaoanu]

I think this is better suited for StackOverflow.

[jbogard]

Reopening to track this — it is a real bug, not just nullable semantics. The third Condition argument is documented as the source member but we were passing the value after conversion to the destination member type, so a null Nullable<T> had already collapsed to default(T) before the condition ran. Fix in #4655.

[jbogard]

Fixed by #4655, merged as 6e8697b — shipping in 16.3.

Condition now receives the value resolved from the source object before conversion to the destination member type when the condition's member parameter can hold it, so a ForAllMembers condition sees a null Nullable<T> instead of default(T). Conditional-mapping.md gained a "Nullable source members" section covering that, the PreCondition route for typed ForMember conditions, UseDestinationValue for the keep-the-destination case, and the ?? default(T) rule when there is no condition.