Simple way to exclude all properties of source or target class except explicitly mapped

[vin-igor]

Is your feature request related to a problem? Please describe.
I have class A with about 70 properties and class B with 29 properties. All properties from class B exist in class A. But I want to map only 10 properties from B to A. Now I'm forced to add 19 [MapperIgnoreSource(nameof(B.Prop1))] attributes to mapper method. With this approach it is simpler to write 10 rows of manual mapping code (a.Prop2 = b.Prop2).

Maybe I'm missing somethiing but didn't find any ability to ignore all props of class with single attribute or something.

Describe the solution you'd like
It will be nice if I be able to add something like this:

[MapperIgnoreSource]
[MapProperty(nameof(B.Prop2), nameof(A.Prop2))]
[MapProperty(nameof(B.Prop3), nameof(A.Prop3))]
public static partial A Map(B b);

or one-liner (the best option):

[MapperIgnoreSource(Except=new[]{nameof(B.Prop2), nameof(B.Prop3)})]
public static partial A Map(B b);

Describe alternatives you've considered
An alternative is do not use Mapperly and write mapping myself for this cases :(

Additional context
None

[latonz]

Thank you for this proposal. In a first iteration I'd suggest implementing it without Except support. I'm also not sure about the name yet, probably OnlyMapExplicitMappedMembers or similar would be better? Also we should introduce a property on the MapperAttribute to handle this.
We would be happy to accept a PR implementing this. A good starting point to contribute is the contributors documentation. Let us know if you plan to work on this 😊

[xaraxarax]

I’d like to add my support for this feature request, as I’m running into a very similar scenario.

In our application, EF entities contain many members that are intentionally not mapped to DTOs:

• audit fields (Created, Changed)
• navigation properties (Color, ItemRefs)
• internal flags (Protected)
• collections
• base‑class members

With RequiredMappingStrategy.Target and TreatWarningsAsErrors, these members currently produce warnings that escalate to errors — even though the mapping is correct and intentional.

Using [MapperIgnoreSource] or [MapperIgnoreTarget] on every single member is not feasible, especially when entities contain dozens of properties. Also, modifying EF/domain models to add ignore attributes is not desirable or even possible in many architectures.

A configuration at the mapper level, as proposed or alternatively:

[Mapper(IgnoreSourceMembers = new[] { nameof(EfEntity.Flag), nameof(EfEntity.Created) })]

or/and

[Mapper(MapSourceMembers = new[] { nameof(EfEntity.Flag), nameof(EfEntity.Created) })]

would solve this cleanly and explicitly.

Why this feature would be valuable

• Explicit & intentional: cleanly documents which members are ignored
• Strict‑mode friendly: DTO properties must still be mapped
• TreatWarningsAsErrors compatible: no false‑positive diagnostics
• No domain model pollution: avoids adding mapping attributes to EF/domain classes
• Refactor‑safe: nameof() keeps everything navigable and compiler‑checked
• Context‑specific: different mappers can ignore different members
• Enterprise‑ready: supports large models with many irrelevant properties

While I understand the conceptual flow of Mapperly, I’m not experienced enough with Roslyn generator internals to implement this feature in a way that would be maintainable and up to the project’s standards. I don’t want to submit a PR that creates long‑term maintenance overhead for the project.

Thanks again for considering this feature — it would be extremely valuable for strict DTO mapping in enterprise‑grade architectures.