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Fix incorrect enum coercion during deserialization from JsonElement #2962

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Merged
sandwwraith merged 1 commit into from
Mar 27, 2025
Merged

Fix incorrect enum coercion during deserialization from JsonElement #2962

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14 changes: 7 additions & 7 deletions formats/json-tests/commonTest/src/kotlinx/serialization/json/JsonCoerceInputValuesTest.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -155,27 +155,27 @@ class JsonCoerceInputValuesTest : JsonTestBase() {
fun testNullableEnumWithoutDefault() {
val j = Json(json) { explicitNulls = false }
parametrizedTest { mode ->
assertEquals(NullableEnumHolder(null), j.decodeFromString("{}"))
assertEquals(NullableEnumHolder(null), j.decodeFromString("""{"enum":"incorrect"}"""))
assertEquals(NullableEnumHolder(null), j.decodeFromString("{}", mode))
assertEquals(NullableEnumHolder(null), j.decodeFromString("""{"enum":"incorrect"}""", mode))
}
}

@Test
fun testNullableEnumWithoutDefaultDoesNotCoerceExplicitly() {
val j = Json(json) { explicitNulls = true }
parametrizedTest { mode ->
assertFailsWith<SerializationException> { j.decodeFromString<NullableEnumHolder>("{}") }
assertFailsWith<SerializationException> { j.decodeFromString<NullableEnumHolder>("""{"enum":"incorrect"}""") }
assertFailsWith<SerializationException> { j.decodeFromString<NullableEnumHolder>("{}", mode) }
assertFailsWith<SerializationException> { j.decodeFromString<NullableEnumHolder>("""{"enum":"incorrect"}""", mode) }
}
}

@Test
fun testNullableEnumWithDefault() {
val j = Json(json) { explicitNulls = false }
parametrizedTest { mode ->
assertEquals(NullableEnumWithDefault(), j.decodeFromString("{}"))
assertEquals(NullableEnumWithDefault(), j.decodeFromString("""{"e":"incorrect"}"""))
assertEquals(NullableEnumWithDefault(null), j.decodeFromString("""{"e":null}"""))
assertEquals(NullableEnumWithDefault(), j.decodeFromString("{}", mode))
assertEquals(NullableEnumWithDefault(), j.decodeFromString("""{"e":"incorrect"}""", mode))
assertEquals(NullableEnumWithDefault(null), j.decodeFromString("""{"e":null}""", mode))
}
}
}
18 changes: 16 additions & 2 deletions formats/json-tests/jsTest/src/kotlinx/serialization/json/JsonCoerceInputValuesDynamicTest.kt
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Expand Up @@ -13,9 +13,9 @@ class JsonCoerceInputValuesDynamicTest {
isLenient = true
}

private fun <T> doTest(inputs: List<dynamic>, expected: T, serializer: KSerializer<T>) {
private fun <T> doTest(inputs: List<dynamic>, expected: T, serializer: KSerializer<T>, jsonImpl: Json = json) {
for (input in inputs) {
assertEquals(expected, json.decodeFromDynamic(serializer, input), "Failed on input: $input")
assertEquals(expected, jsonImpl.decodeFromDynamic(serializer, input), "Failed on input: $input")
}
}

Expand Down Expand Up @@ -49,6 +49,20 @@ class JsonCoerceInputValuesDynamicTest {
}
}

@Test
fun testUseNullWithImplicitNulls() {
val withImplicitNulls = Json(json) { explicitNulls = false }
doTest(
listOf(
js("""{}"""),
js("""{"enum":"incorrect"}"""),
),
JsonCoerceInputValuesTest.NullableEnumHolder(null),
JsonCoerceInputValuesTest.NullableEnumHolder.serializer(),
withImplicitNulls
)
}

@Test
fun testUseDefaultInMultipleCases() {
val testData = mapOf<dynamic, JsonCoerceInputValuesTest.MultipleValues>(
Expand Down
32 changes: 19 additions & 13 deletions formats/json/commonMain/src/kotlinx/serialization/json/internal/TreeJsonDecoder.kt
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Expand Up @@ -197,31 +197,35 @@ private open class JsonTreeDecoder(
) : AbstractJsonTreeDecoder(json, value, polymorphicDiscriminator) {
private var position = 0
private var forceNull: Boolean = false
/*
* Checks whether JSON has `null` value for non-null property or unknown enum value for enum property
*/
private fun coerceInputValue(descriptor: SerialDescriptor, index: Int, tag: String): Boolean =
json.tryCoerceValue(
descriptor, index,
{ currentElement(tag) is JsonNull },
{ (currentElement(tag) as? JsonPrimitive)?.contentOrNull }
)

override fun decodeElementIndex(descriptor: SerialDescriptor): Int {
while (position < descriptor.elementsCount) {
val name = descriptor.getTag(position++)
val index = position - 1
forceNull = false
if ((name in value || absenceIsNull(descriptor, index))
&& (!configuration.coerceInputValues || !coerceInputValue(descriptor, index, name))
) {

if (name in value || setForceNull(descriptor, index)) {
// if forceNull is true, then decodeNotNullMark returns false and `null` is automatically inserted
// by Decoder.decodeIfNullable
if (!configuration.coerceInputValues) return index

if (json.tryCoerceValue(
descriptor, index,
{ currentElementOrNull(name) is JsonNull },
{ (currentElementOrNull(name) as? JsonPrimitive)?.contentOrNull },
{ // an unknown enum value should be coerced to null via decodeNotNullMark if explicitNulls=false :
if (setForceNull(descriptor, index)) return index
}
)
) continue // do not read coerced value

return index
}
}
return CompositeDecoder.DECODE_DONE
}

private fun absenceIsNull(descriptor: SerialDescriptor, index: Int): Boolean {
private fun setForceNull(descriptor: SerialDescriptor, index: Int): Boolean {
forceNull = !json.configuration.explicitNulls
&& !descriptor.isElementOptional(index) && descriptor.getElementDescriptor(index).isNullable
return forceNull
Expand Down Expand Up @@ -257,6 +261,8 @@ private open class JsonTreeDecoder(

override fun currentElement(tag: String): JsonElement = value.getValue(tag)

fun currentElementOrNull(tag: String): JsonElement? = value[tag]

override fun beginStructure(descriptor: SerialDescriptor): CompositeDecoder {
// polyDiscriminator needs to be preserved so the check for unknown keys
// in endStructure can filter polyDiscriminator out.
Expand Down
19 changes: 17 additions & 2 deletions formats/json/jsMain/src/kotlinx/serialization/json/internal/DynamicDecoders.kt
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Expand Up @@ -85,7 +85,22 @@ private open class DynamicInput(
val name = descriptor.getTag(currentPosition++)
val index = currentPosition - 1
forceNull = false
if ((hasName(name) || absenceIsNull(descriptor, index)) && (!json.configuration.coerceInputValues || !coerceInputValue(descriptor, index, name))) {

if (hasName(name) || setForceNull(descriptor, index)) {
// if forceNull is true, then decodeNotNullMark returns false and `null` is automatically inserted
// by Decoder.decodeIfNullable
if (!json.configuration.coerceInputValues) return index

if (json.tryCoerceValue(
descriptor, index,
{ getByTag(name) == null },
{ getByTag(name) as? String },
{ // an unknown enum value should be coerced to null via decodeNotNullMark if explicitNulls=false :
if (setForceNull(descriptor, index)) return index
}
)
) continue // do not read coerced value

return index
}
}
Expand All @@ -94,7 +109,7 @@ private open class DynamicInput(

private fun hasName(name: String) = value[name] !== undefined

private fun absenceIsNull(descriptor: SerialDescriptor, index: Int): Boolean {
private fun setForceNull(descriptor: SerialDescriptor, index: Int): Boolean {
forceNull = !json.configuration.explicitNulls
&& !descriptor.isElementOptional(index) && descriptor.getElementDescriptor(index).isNullable
return forceNull
Expand Down