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Incorporate JsonPath into exception messages (#1841)
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141 changes: 141 additions & 0 deletions
141
formats/json/commonMain/src/kotlinx/serialization/json/internal/JsonPath.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,141 @@ | ||
| package kotlinx.serialization.json.internal | ||
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| import kotlinx.serialization.* | ||
| import kotlinx.serialization.descriptors.* | ||
| import kotlinx.serialization.internal.* | ||
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| /** | ||
| * Internal representation of the current JSON path. | ||
| * It is stored as the array of serial descriptors (for regular classes) | ||
| * and `Any?` in case of Map keys. | ||
| * | ||
| * Example of the state when decoding the list | ||
| * ``` | ||
| * class Foo(val a: Int, val l: List<String>) | ||
| * | ||
| * // {"l": ["a", "b", "c"] } | ||
| * | ||
| * Current path when decoding array elements: | ||
| * Foo.descriptor, List(String).descriptor | ||
| * 1 (index of the 'l'), 2 (index of currently being decoded "c") | ||
| * ``` | ||
| */ | ||
| internal class JsonPath { | ||
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| // Tombstone indicates that we are within a map, but the map key is currently being decoded. | ||
| // It is also used to overwrite a previous map key to avoid memory leaks and misattribution. | ||
| object Tombstone | ||
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| /* | ||
| * Serial descriptor, map key or the tombstone for map key | ||
| */ | ||
| private var currentObjectPath = arrayOfNulls<Any?>(8) | ||
| /* | ||
| * Index is a small state-machine used to determine the state of the path: | ||
| * >=0 -> index of the element being decoded with the outer class currentObjectPath[currentDepth] | ||
| * -1 -> nested elements are not yet decoded | ||
| * -2 -> the map is being decoded and both its descriptor AND the last key were added to the path. | ||
| * | ||
| * -2 is effectively required to specify that two slots has been claimed and both should be | ||
| * cleaned up when the decoding is done. | ||
| * The cleanup is essential in order to avoid memory leaks for huge strings and structured keys. | ||
| */ | ||
| private var indicies = IntArray(8) { -1 } | ||
| private var currentDepth = -1 | ||
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| // Invoked when class is started being decoded | ||
| fun pushDescriptor(sd: SerialDescriptor) { | ||
| val depth = ++currentDepth | ||
| if (depth == currentObjectPath.size) { | ||
| resize() | ||
| } | ||
| currentObjectPath[depth] = sd | ||
| } | ||
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| // Invoked when index-th element of the current descriptor is being decoded | ||
| fun updateDescriptorIndex(index: Int) { | ||
| indicies[currentDepth] = index | ||
| } | ||
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| /* | ||
| * For maps we cannot use indicies and should use the key as an element of the path instead. | ||
| * The key can be even an object (e.g. in a case of 'allowStructuredMapKeys') where | ||
| * 'toString' is way too heavy or have side-effects. | ||
| * For that we are storing the key instead. | ||
| */ | ||
| fun updateCurrentMapKey(key: Any?) { | ||
| // idx != -2 -> this is the very first key being added | ||
| if (indicies[currentDepth] != -2 && ++currentDepth == currentObjectPath.size) { | ||
| resize() | ||
| } | ||
| currentObjectPath[currentDepth] = key | ||
| indicies[currentDepth] = -2 | ||
| } | ||
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| /** Used to indicate that we are in the process of decoding the key itself and can't specify it in path */ | ||
| fun resetCurrentMapKey() { | ||
| if (indicies[currentDepth] == -2) { | ||
| currentObjectPath[currentDepth] = Tombstone | ||
| } | ||
| } | ||
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| fun popDescriptor() { | ||
| // When we are ending map, we pop the last key and the outer field as well | ||
| val depth = currentDepth | ||
| if (indicies[depth] == -2) { | ||
| indicies[depth] = -1 | ||
| currentDepth-- | ||
| } | ||
| // Guard against top-level maps | ||
| if (currentDepth != -1) { | ||
| // No need to clean idx up as it was already cleaned by updateDescriptorIndex(DECODE_DONE) | ||
| currentDepth-- | ||
| } | ||
| } | ||
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| @OptIn(ExperimentalSerializationApi::class) | ||
| fun getPath(): String { | ||
| return buildString { | ||
| append("$") | ||
| repeat(currentDepth + 1) { | ||
| val element = currentObjectPath[it] | ||
| if (element is SerialDescriptor) { | ||
| if (element.kind == StructureKind.LIST) { | ||
| if (indicies[it] != -1) { | ||
| append("[") | ||
| append(indicies[it]) | ||
| append("]") | ||
| } | ||
| } else { | ||
| val idx = indicies[it] | ||
| // If an actual element is being decoded | ||
| if (idx >= 0) { | ||
| append(".") | ||
| append(element.getElementName(idx)) | ||
| } | ||
| } | ||
| } else if (element !== Tombstone) { | ||
| append("[") | ||
| // All non-indicies should be properly quoted by JsonPath convention | ||
| append("'") | ||
| // Else -- map key | ||
| append(element) | ||
| append("'") | ||
| append("]") | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| @OptIn(ExperimentalSerializationApi::class) | ||
| private fun prettyString(it: Any?) = (it as? SerialDescriptor)?.serialName ?: it.toString() | ||
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| private fun resize() { | ||
| val newSize = currentDepth * 2 | ||
| currentObjectPath = currentObjectPath.copyOf(newSize) | ||
| indicies = indicies.copyOf(newSize) | ||
| } | ||
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| override fun toString(): String = getPath() | ||
| } |
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