Moshi: Codegen not considering `@Json` annotation on superclass constructor parameters.

[NightlyNexus]

abstract class Superclass(@Json(name="superclassPropertyJsonName") var superclassProperty: String? = null)

@JsonClass(generateAdapter = true)
class Subclass(@Json(name="subclassPropertyJsonName") val subclassProperty: String? = null) : Superclass()

@Test fun subclass() {
  val moshi = Moshi.Builder().build()
  val jsonAdapter = moshi.adapter(Subclass::class.java)

  val encoded = Subclass("hello").apply { superclassProperty = "world" }
  assertThat(jsonAdapter.toJson(encoded)).isEqualTo("""{"subclassPropertyJsonName":"hello","superclassPropertyJsonName":"world"}""")

  val decoded = jsonAdapter.fromJson("""{"superclassPropertyJsonName":"world","subclassPropertyJsonName":"hello"}""")!!
  assertThat(decoded.subclassProperty).isEqualTo("hello")
  assertThat(decoded.superclassProperty).isEqualTo("world")
}

fails.

via https://github.com/square/moshi/issues/495#issuecomment-425401941

[swankjesse]

This is working as intended. This is because the subclass is explicitly initializing that value to it's default here: : Superclass().

[NightlyNexus]

marking the target as property makes the test case above pass.

abstract class Superclass(@property:Json(name="superclassPropertyJsonName") var superclassProperty: String? = null)

seems inconsistent?

[swankjesse]

At no point can Moshi call the superclass‘ constructor. It doesn't use it, and it cannot use it. But it can set properties.

[NightlyNexus]

right.
i'm confused and curious why @property:Json vs @Json makes a difference. I would have expected the @Json to be applied to the var property, without needing the explicit @property:Json.

[swankjesse]

I think it’s cause @property:Json is visible to callers of subtypes; but the supertype constructor’s parameters are not.

[NightlyNexus]

yeah! got it, thank you.