Summary

Issue is reproduced when using the 5.4.0 driver.

When creating a mongo path to a property containing a filtered positional operator, the resulting path may be incorrect. The following snippet shows how to reproduce an incorrect path:

import com.mongodb.kotlin.client.model.filteredPosOp
import com.mongodb.kotlin.client.model.path
import org.bson.types.ObjectId

data class Document(
    val _id: ObjectId,
    val elements: List<String>,
)

fun main() {
    var incorrectPathFound = false
    var index = 0

    while (!incorrectPathFound) {
        val path = Document::elements.filteredPosOp("identifier$index").path()
        val expectedPath = "elements.$[identifier$index]"

        incorrectPathFound = path != expectedPath

        if (incorrectPathFound) {
            println("Incorrect path for index $index: path is $path but should be $expectedPath")
        }
        index++
    }
} 

The snippet can be found this repo: https://github.com/brigondaud-betclic/mongo-java-driver-5.4.0-bug 

A possible output of this snippet is: 

Incorrect path for index 102115: path is elements.$[identifier58628] but should be elements.$[identifier102115]

Issue seems related to instances of KPropertyPath.CustomProperty. When resolving a path using the com.mongodb.kotlin.client.model.path method, instances of this class are stored in the pathCache using the default toString method. A cache hit may happen in case of hashCode conflicts when resolving another path with a CustomProperty instance, producing an incorrect property name.