Support array content equality when deciding whether to encode a default value

[drewhamilton]

What is your use-case and why do you need this feature?

For most properties, the behavior of encodeDefaults or @EncodeDefault is determined by an equals check against the property's default value: If encodeDefaults is false and equals is true, the property doesn't get included when serialized.

For array properties, this doesn't work well, because arrays don't implement content-based equals. Thus, for example, an empty array property value registers as not-equals to the empty array default property value, and the empty array is included in the serialized output.

cashapp/redwood#1395 wants to migrate its public API List properties to Array types, primarily because of performance impact on JS.

Describe the solution you'd like

Support content-based rather than reference-based comparison when determining the encodeDefaults behavior for array properties. This could be by default or via a property annotation.

[sandwwraith]

Given that .equals on arrays aren't as useful, I think the behavior can be changed. Although, it has to be a bugfix in compiler plugin, so it will take some time until it's available in the Kotlin release

[drewhamilton]

Any thoughts on when this could be implemented? Any chance of landing around Kotlin 2.0 release?

[sandwwraith]

Tbh I forgot about this, so it does not have any plans or particular date

[JakeWharton]

Now that Kotlin 2.0 is out do you think this is something that could be put into future consideration?

[sandwwraith]

Yes, I think it is something that can be done now