[API Proposal]: Support for selecting multiple properties in single expression.

[voroninp]

Background and motivation

If I write assertion this way:

 actualEnv.Should().BeEquivalentTo(env, _ => _.Excluding(_ => new { _.Id, _.Creator, _.LastEditor }));

the exception is thrown:

System.ArgumentException : Expression <new <>f__AnonymousType0`3(Id = _.Id, Creator = _.Creator, LastEditor = _.LastEditor)> cannot be used to select a member. (Parameter 'expression')

So I have to write it slightly more verbose.

 actualEnv.Should().BeEquivalentTo(env, _ => _.Excluding(_ => _.Id).Excluding(_ => _.Creator).Excluding(_ => _.LastEditor));

API Proposal

So, my proposal is to treat expression for anonymous object creation as an enumeration of properties to exclude.
For example EF Core uses this approach for defining composite key.

API Usage

a.Shoul().BeEquivalentTo(b, _ => _.Excluding(b => new { b.Prop1, ...., b.PropN }));

Alternative Designs

No response

Risks

No response

Are you willing to help with a proof-of-concept (as PR in that or a separate repo) first and as pull-request later on?

No

[IT-VBFK]

I assume that should be only possible for Excluding(), .For().Exclude() and Including() and nothing else?

Asking, because strictly speaking e.g. subject.Should().BeEquivalentTo(expected, opt => opt.WithStrictOrderingFor(o => new { o.prop1, o.prop2 })); would also be possible (from API perspective, but makes little sense.. at least for me 🙂). That's why I am limiting this to the first element if applicable.

What does the rest think?

[voroninp]

but makes little sense

Why do you think so? 🤔 AFAIK this is also a way of defining ordering, at least for some frameworks.

dotnet/efcore#19367

[IT-VBFK]

Huh.. that's true
Will also add this to a few missing options

[voroninp]

@IT-VBFK , on the other hand, linq throws because anonymous types do not implement IComparable.

var a = new []
{
    new { x = 1, y = -1},
    new { x = -1, y = 1}
};
a[0].GetType().Dump();
a.Order().ToList();

[ITaluone]

The question is: What do we want to achieve here?
IMO: excluding/including as non-verbose as possible. And possibly ordering?

[dennisdoomen]

Please refrain from creating a PR until we ask for it or we label the issue as api-approved

[IT-VBFK]

Ok,

I converted it to a draft. But I leave it open. Take it as a sketch 😉