Option to omit toString generation

[drewhamilton]

Generated toString implementations add to the string pool, and can't be removed by optimizers like R8 due to the general widely-used nature of toString. For this reason it is desirable in some contexts to skip toString—only generate equals and hashCode—on internal value types. It would be nice if Poko had a way to do this for some, but not all, classes in a module/project.

In the meantime, it's possible to achieve the desired behavior manually:

@Poko class Thing(
    val property: OtherThing,
) {
    override fun toString(): String = super.toString()
}

[drewhamilton]

There are a few API design options that come to mind. These all interact with #67's design in some way, so probably both designs need to be fleshed out at the same time.

1. Add a separate class-level annotation: @DisableToStringGeneration @Poko class Blah(...). This is the simplest to implement. But it's not as concise as other options. It doesn't scale well if we want other class-level behavior customizations. Doesn't play well with one Cache computed hashCode and toString for deeply immutable types #67 proposal, which is to add @Memoized to each function declaration—what should happen if this annotation is used but @Memoized is also added to toString?

2. Add a property to the existing @Poko annotation: @Poko(generateToString = false). More concise and scales better than (1), but maybe still not super well. Doesn't play well with the same Cache computed hashCode and toString for deeply immutable types #67 approach that (1) doesn't play well with—what should happen if generateToString is false but @Memoized is also added to toString?

3. Add a property for each of the three generated functions to @Poko, and use an enum to define each value. This seems like it would scale better. But it feels weird to sort of write functions inside an annotation. And it's not clear what should happen if someone explicitly chooses one of these options but manually overrides the corresponding function at the same time.

@Poko(
    equals = INCLUDED|EXCLUDED|MEMOIZED,
    hashCode = INCLUDED|EXCLUDED|MEMOIZED,
    toString = INCLUDED|EXCLUDED|MEMOIZED,
)

4. Stick with the workaround listed above. This may be the best option if all the others require compromises.