Serialising an object with a String field containing certain JSON crashes with java.lang.ArrayIndexOutOfBoundsException

[timorantalaiho]

Describe the bug

Serialising an object with a String field containing certain JSON crashes with java.lang.ArrayIndexOutOfBoundsException:

CrashingJsonSerializationTest > bar() FAILED
    java.lang.ArrayIndexOutOfBoundsException: Index 128 out of bounds for length 128
        at kotlinx.serialization.json.internal.JsonStringBuilder.appendStringSlowPath(JsonStringBuilder.kt:102)
        at kotlinx.serialization.json.internal.JsonStringBuilder.appendQuoted(JsonStringBuilder.kt:61)
        at kotlinx.serialization.json.internal.Composer.printQuoted(Composers.kt:42)
        at kotlinx.serialization.json.internal.StreamingJsonEncoder.encodeString(StreamingJsonEncoder.kt:203)
        at kotlinx.serialization.encoding.AbstractEncoder.encodeStringElement(AbstractEncoder.kt:65)
        at CrashingJsonSerializationTest$MyObject$$serializer.serialize(CrashingJsonSerialisation.kt:13)
        at CrashingJsonSerializationTest$MyObject$$serializer.serialize(CrashingJsonSerialisation.kt:13)
        at kotlinx.serialization.json.internal.StreamingJsonEncoder.encodeSerializableValue(StreamingJsonEncoder.kt:211)
        at kotlinx.serialization.json.Json.encodeToString(Json.kt:80)
        at CrashingJsonSerializationTest.bar(CrashingJsonSerialisation.kt:10)

I tried to create a minimal input to reproduce the problem, based on the input we first experienced it with.

To Reproduce

import kotlinx.serialization.Serializable
import kotlinx.serialization.json.Json
import org.junit.jupiter.api.Test

class CrashingJsonSerializationTest {
    @Test
    fun bar() {
        val failingString = "{\"status\":123,\"message\":\"content\",\"path\":\"/here/beeeeeeeeeeee/dragoons/d63574f-705c-49dd-a6bc-c8d1e524eefd/\"}"
        val o = MyObject(failingString)
        System.err.println(Json.encodeToString(MyObject.serializer(), o))
    }

    @Serializable
    data class MyObject(val text: String)
}

See a complete reproducible project at https://github.com/timorantalaiho/kotlin-json-crash .

Expected behavior

Object should be serialised with the String properly escaped.
Serialisation should not crash, regardless of the contents of the String.

Environment

• Kotlin version: 1.5.0
• Library version: 1.2.0
• Kotlin platforms: OpenJDK 11 (openjdk version "11.0.11" 2021-04-20)
• Gradle version: 6.8

[timorantalaiho]

Hey: looks like this is a duplicate of #1441