Properties serialization incorrect behavior

[FerrumBrain]

0. Setup

We created the following class hierarchy for testing serialization library:

Value (org.plan.research)
    ArrayValue (org.plan.research)
    BooleanArrayValue (org.plan.research)
    BooleanValue (org.plan.research)
    ByteArrayValue (org.plan.research)
    ByteValue (org.plan.research)
    CharArrayValue (org.plan.research)
    CharValue (org.plan.research)
    CompositeNullableValue (org.plan.research)
    DefaultValueAlways (org.plan.research)
    DefaultValueNever (org.plan.research)
    DoubleArrayValue (org.plan.research)
    DoubleValue (org.plan.research)
    EnumValue (org.plan.research)
    FloatArrayValue (org.plan.research)
    FloatValue (org.plan.research)
    IntArrayValue (org.plan.research)
    IntValue (org.plan.research)
    ListValue (org.plan.research)
    LongArrayValue (org.plan.research)
    LongValue (org.plan.research)
    NullValue (org.plan.research)
    ObjectValue (org.plan.research)
    ShortArrayValue (org.plan.research)
    ShortValue (org.plan.research)
    StringValue (org.plan.research)

Value hierarchy tries to use most of the available serialization API and test it on all main data types available on Kotlin/JVM. The exact implementation details are not important in most cases. We will highlight interesting implementation details whenever necessary.

1. Empty primitive arrays are not serialized

Empty primitive arrays are not present in any way in the encoded string. Documentation does not specify behavior in that case.

The same exception can be achieved with null value fields, but that behavior is documented.

@OptIn(ExperimentalSerializationApi::class)
@Test
fun `missing field for empty primitive array`() {
    val value: Value = BooleanArrayValue(booleanArrayOf())
    val strMap = Properties.encodeToStringMap(value)
    // Fails with
    // "kotlinx.serialization.MissingFieldException: Field 'value' is required for type with serial name 'org.plan.research.BooleanArrayValue', but it was missing"
    val decodedValue = Properties.decodeFromStringMap<Value>(strMap)
    assertTrue { value == decodedValue }
}

Bugs are found by fuzzing team @ PLAN Lab

Environment

• Kotlin version: 2.0.20
• Library version: 1.7.3
• Kotlin platforms: JVM
• Gradle version: 8.8