Add `@SourcePropertyName` to handle a property name of the source object

[filiphr]

A suggestion from #3313 (comment)

[filiphr]

We might actually need a new @SourcePropertyName to have the source property. Currently all our tests use implicit mapping, and in this case the source and target property names are identical.

[filiphr]

Discussed with the team we are going to add @SourcePropertyName that would pass the name of the source property and @TargetPropertyName that would pass the target property name

[aboqasem]

Hello @filiphr & @babyfish-ct, I do not see where's the confusion in the name. It's indeed getting the target's property name as the name says. I added a test case that proves that: aboqasem@76e7067.

Am I missing something?

[thunderhook]

@aboqasem I looked at the tests and the code and yes, indeed. The @TargetPropertyName handles the targets property name. So there will be an additional @SourcePropertyName annotation which handles the sources property name. I will rename this ticket to avoid any further confusion.

[aboqasem]

Thank you @thunderhook!

This is my first time contributing to MapStruct. May I try to contribute to implementing this?

I started doing it and currently trying to understand what are the .ftl files (seems like they are for code gen). Then perhaps start with the org.mapstruct.ap.MappingProcessor class?

Any tips or pointers would help!

[thunderhook]

What I would do in your case: Take a look at the commit where the @TargetPropertyName was introduced to see out how it works. I think the code for the @SourcePropertyName will be very similar.

Yes, the .ftl files are Apache FreeMarker java templates which are used for the code generation of mappers (and all of their belongings). The org.mapstruct.ap.internal.processor.MapperCreationProcessor is the main processor that handles the creation of a mapper class.

Another hint: When you run a test, e.g. the TargetPropertyNameTest, you can have a look at the generated sources and mappers that are generated and compiled in: ...\mapstruct\processor\target\compilation-tests\org.mapstruct.ap.test.conditional.targetpropertyname.TargetPropertyNameTest.

If it is okay with @filiphr (I don't know if he's currently working on this issue) you are welcome to contribute!

[aboqasem]

Thanks a lot, @thunderhook!

I was looking for the generated classes in the wrong place, thanks for the hint!

Let me try to check the good-first-issues first, since there's 5 of them at the moment.