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Ensure custom KProperty include the name in the hashcode #1710

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Merged
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May 19, 2025
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Merged

Ensure custom KProperty include the name in the hashcode #1710

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03de645
Ensure custom KProperty include the name in the hashcode
rozza May 7, 2025
0764544
PR - simplify the cache key
rozza May 12, 2025
b345e4b
Spotless update
rozza May 12, 2025
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3 changes: 1 addition & 2 deletions driver-kotlin-extensions/src/main/kotlin/com/mongodb/kotlin/client/model/Properties.kt
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Expand Up @@ -71,8 +71,7 @@ public fun <T> KProperty<T>.path(): String {
return if (this is KPropertyPath<*, T>) {
this.name
} else {
pathCache.computeIfAbsent(this.toString()) {

pathCache.computeIfAbsent("${this.javaClass.getSimpleName()}@${Integer.toHexString(hashCode())}") {
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Good catch!

Can't we just refactor the map to

private val pathCache: MutableMap<Int, String> by lazySoft { ConcurrentHashMap<Int, String>() }

then use the hashCode

pathCache.computeIfAbsent(this.hashCode())

not sure why you concatenate the class name with the hash?

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I suppose I followed the previous logic for the key.

Hashcodes alone don't provide enough protection from collisions:

    data class Name(val name: String)
    data class School(val house: String)

    @Test
    fun testToString() {
        assertEquals(Name("Merlin").hashCode(), School("Merlin").hashCode())
    }

In this case they appear to - I tested up to 2 million for naming collisions but I still have some concern that it could also cause an issue. What do you think?

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The hashcode is calculated for the KProperty1 so it will only match if you're using the same KProperty1

data class Name(val name: String)
data class School(val name: String)

val p1: KProperty1<Name, String> = Name::name
val p2: KProperty1<School, String> = School::name

println(p1.hashCode())            // 2000641095
println(Name::name.hashCode())    // 2000641095
println(School::name.hashCode())  // -1039559637

// Check serial name - Note kotlinx.serialization.SerialName may not be on the class
// path
val serialName =
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17 changes: 17 additions & 0 deletions driver-kotlin-extensions/src/main/kotlin/com/mongodb/kotlin/client/property/KPropertyPath.kt
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Expand Up @@ -20,6 +20,7 @@ package com.mongodb.kotlin.client.property

import com.mongodb.annotations.Sealed
import com.mongodb.kotlin.client.model.path
import java.util.Objects
import kotlin.reflect.KParameter
import kotlin.reflect.KProperty1
import kotlin.reflect.KType
Expand Down Expand Up @@ -84,6 +85,15 @@ public open class KPropertyPath<T, R>(
override fun callBy(args: Map<KParameter, Any?>): R = unSupportedOperation()
override fun get(receiver: T): R = unSupportedOperation()
override fun getDelegate(receiver: T): Any? = unSupportedOperation()
override fun hashCode(): Int = Objects.hash(previous, property, name)
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It's a good idea to provide the hashCode and equals but these weren't involved in the code path since we return the name directly if the instance is KPropertyPath in

return if (this is KPropertyPath<*, T>) {
        this.name

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Not used for the direct path, but the hashcode for CustomProperty relies on the hashcode.

override fun equals(other: Any?): Boolean {
if (this === other) return true
if (javaClass != other?.javaClass) return false
other as KPropertyPath<*, *>
return Objects.equals(previous, other.previous) &&
Objects.equals(property, other.property) &&
Objects.equals(name, other.name)
}

public companion object {

Expand Down Expand Up @@ -121,6 +131,13 @@ public open class KPropertyPath<T, R>(
override fun get(receiver: T): R = unSupportedOperation()
override fun getDelegate(receiver: T): Any? = unSupportedOperation()
override fun invoke(p1: T): R = unSupportedOperation()
override fun hashCode(): Int = Objects.hash(previous, name)
override fun equals(other: Any?): Boolean {
if (this === other) return true
if (javaClass != other?.javaClass) return false
other as CustomProperty<*, *>
return Objects.equals(previous, other.previous) && Objects.equals(name, other.name)
}
}

/** Provides "fake" property with custom name. */
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14 changes: 14 additions & 0 deletions driver-kotlin-extensions/src/test/kotlin/com/mongodb/kotlin/client/model/KPropertiesTest.kt
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Expand Up @@ -139,4 +139,18 @@ class KPropertiesTest {
assertThrows<UnsupportedOperationException> { property.get(restaurant) }
assertThrows<UnsupportedOperationException> { property.getDelegate(restaurant) }
}

@Test
fun testNoCacheCollisions() {
for (i in 1.rangeTo(25_000)) {
assertEquals("reviews.$i", Restaurant::reviews.pos(i).path())
assertEquals("reviews.$[identifier$i]", Restaurant::reviews.filteredPosOp("identifier$i").path())
assertEquals("localeMap.$i", Restaurant::localeMap.keyProjection(i).path())

val x = i / 2
assertEquals("reviews.$[identifier$x].rating", (Restaurant::reviews.filteredPosOp("identifier$x") / Review::score).path())
assertEquals("reviews.$x.rating", (Restaurant::reviews.pos(x) / Review::score).path())
assertEquals("localeMap.$x.rating", (Restaurant::localeMap.keyProjection(x) / Review::score).path())
}
}
}