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lemniklemnik
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feat(json): added a simple json element extractor
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‎bugsnag-android-core/src/main/java/com/bugsnag/android/internal/json/JsonCollectionPath.kt‎

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package com.bugsnag.android.internal.json
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/**
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* A simple path implementation similar to json path, but much simpler. The notation is strictly
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* dot (`'.'`) separated and does not support name escaping. Paths are parsed from strings and
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* can be efficiently evaluated any number of times once parsed, and are thread safe.
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*
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* Paths are in the form `"property.0.-1.*.value"` where `'*'` is a wildcard match, `0` is the
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* first item of an array (or a property named `"0"`) and `-1` is the last element in an array (or
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* a property named `"-1"`). Null values or non-existent values are skipped.
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*/
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internal class JsonCollectionPath private constructor(
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private val root: PathNode,
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private val path: String
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) {
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/**
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* Extract all of the selected values from the given JSON object stored in the given `Map`.
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*/
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fun extractFrom(json: Map<String, *>): List<Any> {
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val out = ArrayList<Any>()
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root.visit(json, out::add)
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return out
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}
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override fun toString(): String {
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return path
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}
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companion object {
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val IDENTITY_PATH = JsonCollectionPath(PathNode.TerminalNode, "")
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fun fromString(path: String): JsonCollectionPath {
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if (path.isEmpty()) {
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return IDENTITY_PATH
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}
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val segments = path.split('.')
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.reversed() // we build the path backwards
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var node: PathNode = PathNode.TerminalNode
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segments.forEach { segment ->
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node = segment.toPathNode(node)
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}
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return JsonCollectionPath(node, path)
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}
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private fun String.toPathNode(next: PathNode): PathNode {
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if (this == "*") {
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return PathNode.Wildcard(next)
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}
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val index = this.toIntOrNull()
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if (index != null) {
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return if (index < 0) {
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PathNode.NegativeIndex(index, next)
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} else {
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PathNode.PositiveIndex(index, next)
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}
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}
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return PathNode.Property(this, next)
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}
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}
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private sealed class PathNode {
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abstract fun visit(element: Any, collector: (Any) -> Unit)
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abstract class NonTerminalPathNode(protected val next: PathNode) : PathNode()
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class Property(val name: String, next: PathNode) : NonTerminalPathNode(next) {
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override fun visit(element: Any, collector: (Any) -> Unit) {
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if (element is Map<*, *>) {
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element[name]?.let { next.visit(it, collector) }
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}
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}
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override fun toString(): String = name
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}
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class Wildcard(next: PathNode) : NonTerminalPathNode(next) {
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override fun visit(element: Any, collector: (Any) -> Unit) {
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if (element is Iterable<*>) {
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element.forEach { item ->
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item?.let { next.visit(it, collector) }
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}
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} else if (element is Map<*, *>) {
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element.values.forEach { item ->
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item?.let { next.visit(it, collector) }
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}
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}
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}
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}
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abstract class IndexPathNode(
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protected val index: Int,
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next: PathNode
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) : NonTerminalPathNode(next) {
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protected abstract fun normalisedIndex(list: List<*>): Int
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override fun visit(element: Any, collector: (Any) -> Unit) {
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if (element is List<*>) {
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val normalised = normalisedIndex(element)
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element.getOrNull(normalised)?.let { next.visit(it, collector) }
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} else if (element is Map<*, *>) {
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val value = element[index.toString()]
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value?.let { next.visit(it, collector) }
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}
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}
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}
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class PositiveIndex(index: Int, next: PathNode) : IndexPathNode(index, next) {
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override fun normalisedIndex(list: List<*>): Int {
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return index
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}
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}
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class NegativeIndex(index: Int, next: PathNode) : IndexPathNode(index, next) {
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override fun normalisedIndex(list: List<*>): Int {
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return list.size + index
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}
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}
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object TerminalNode : PathNode() {
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override fun visit(element: Any, collector: (Any) -> Unit) {
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collector(element)
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}
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}
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}
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}

‎bugsnag-android-core/src/test/java/com/bugsnag/android/internal/json/JsonCollectionPathTest.kt‎

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package com.bugsnag.android.internal.json
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import com.bugsnag.android.internal.JsonCollectionParser
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import org.junit.Assert.assertEquals
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import org.junit.Assert.assertNotNull
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import org.junit.Test
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internal class JsonCollectionPathTest {
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@Test
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fun extractLastArrayElement() {
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val extracted = extractPathFromResource(
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"metaData.structuralTests.arrayTests.nested.*.-1",
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"event_serialization_9.json"
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)
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assertEquals(
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listOf(2L, listOf(4L, 5L), listOf(7L, listOf(8L, 9L))),
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extracted
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)
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}
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@Test
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fun extractFirstArrayElement() {
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val extracted = extractPathFromResource(
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"metaData.structuralTests.arrayTests.nested.*.0",
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"event_serialization_9.json"
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)
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assertEquals(
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listOf(1L, 3L, 6L),
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extracted
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)
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}
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@Test
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fun nonExistentPropertyPath() {
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val extracted = extractPathFromResource(
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"metaData.structuralTests.arrayTests.noValueHere",
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"event_serialization_9.json"
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)
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assertEquals(0, extracted.size)
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}
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@Test
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fun nonExistentNumericPath() {
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val extracted = extractPathFromResource(
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"metaData.structuralTests.arrayTests.0",
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"event_serialization_9.json"
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)
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assertEquals(0, extracted.size)
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}
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@Test
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fun nonExistentNegativeNumericPath() {
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val extracted = extractPathFromResource(
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"metaData.structuralTests.arrayTests.-1",
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"event_serialization_9.json"
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)
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assertEquals(0, extracted.size)
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}
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@Test
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fun numericMapKeys() {
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val numberKeys = extractPathFromResource("metaData.numbers.0", "path_fixture.json")
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assertEquals(listOf("naught"), numberKeys)
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}
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@Test
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fun wildcardArrayElements() {
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val numberKeys =
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extractPathFromResource("metaData.arrayOfObjects.*.name", "path_fixture.json")
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assertEquals(listOf("one", "two", "three"), numberKeys)
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}
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@Test
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fun wildcardObjectProperties() {
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val numberKeys = extractPathFromResource("metaData.numbers.*", "path_fixture.json")
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assertEquals(listOf("naught", "one", "two", "three"), numberKeys)
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}
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@Test
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fun toStringReturnsPath() {
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val path = "name.string.more words are here.0.-1.*.*.*.\uD83D\uDE00\uD83D\uDE03\uD83D\uDE04"
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val json = JsonCollectionPath.fromString(path)
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assertEquals(path, json.toString())
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}
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private fun extractPathFromResource(path: String, resource: String): List<Any> {
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val json = JsonCollectionParser(this::class.java.getResourceAsStream("/$resource")!!)
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.parse()
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val collectionPath = JsonCollectionPath.fromString(path)
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assertNotNull("path failed to parse: '$path'", collectionPath)
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@Suppress("UNCHECKED_CAST")
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return collectionPath.extractFrom(json as Map<String, *>)
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}
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}

‎bugsnag-android-core/src/test/resources/path_fixture.json‎

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{
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"metaData": {
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"numbers": {
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"0": "naught",
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"1": "one",
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"2": "two",
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"3": "three"
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},
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"arrayOfObjects": [
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{
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"name": "one"
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},
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{
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"name": "two"
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},
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{
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"name": "three"
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}
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]
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}
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}

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