Add updateOnlyNotNullProperties boolean in order to update only not null properties

[qcho]

Hi,

I'm trying to perform partial updates based on the fact that ObjectMappingConfiguration.serializeNull = false. So i expect that my Document doesn't serialize field2 when it's value is null. Obviously i'm using kmongo-native

Am I interpreting this feature wrong?? btw no documentation on this topic anywhere. Here is a Unit test I've made explaining the behavior

import org.bson.codecs.pojo.annotations.BsonId
import org.litote.kmongo.* //NEEDED! import KMongo extensions
import org.litote.kmongo.util.ObjectMappingConfiguration
import kotlin.test.Test
import kotlin.test.assertEquals
import kotlin.test.assertNotNull

class AppTest {

    data class Document(
            @BsonId val id: Int,
            val field1: String,
            val field2: String?
    )

    @Test fun testMongoBehaviours() {
        val client = KMongo.createClient()
        val database = client.getDatabase("test")
        val col = database.getCollection<Document>()
        ObjectMappingConfiguration.serializeNull = false // This is the default value anyway. Just being verbose
        run {
            col.save(Document(1, "Hello1", null))
            val document = col.findOne(Document::id eq 1)
            assertNotNull(document)
            assertEquals("Hello1", document.field1)
            assertEquals(null, document.field2)
        }
        run {
            col.save(Document(1, "Hello2", "World2"))
            val document = col.findOne(Document::id eq 1)
            assertNotNull(document)
            assertEquals("Hello2", document.field1)
            assertEquals("World2", document.field2)
        }
        run {
            col.save(Document(1, "Hello3", null))
            val document = col.findOne(Document::id eq 1)
            assertNotNull(document)
            assertEquals("Hello3", document.field1)
            assertEquals("World2", document.field2) // EXCEPTION THIS LINE. I expect this null value not to be serialized
        }
    }
}

I get

java.lang.AssertionError: 
Expected :World2
Actual   :null

[qcho]

On further investigation I think the issue is at PojoClassMappingTypeService.kt

    override fun filterIdToBson(obj: Any): BsonDocument {
        val bsonDocument = BsonDocument()
        val bsonWriter = BsonDocumentWriter(bsonDocument)
        codecRegistryWithNullSerialization // <--- HERE is always using WithNullSerialization
            .get(obj.javaClass)
            ?.encode(
                bsonWriter,
                obj,
                EncoderContext.builder().build()
            )
        bsonDocument.remove("_id")
        return bsonDocument
    }

Maybe it needs to call ClassMappingType.codecRegistry(MongoClientSettings.getDefaultCodecRegistry()) the same as ::toExtendedJson does?

[qcho]

I've fixed the issue. Sending a pull request now.

It was a mix of two things.
First: PojoClassMappingTypeService was wrong due to #115 (comment)
Second: I was wrong on the usage of save() because it doesn't perform updateOne, instead it does a replaceOne following mongodb's spec.

So doing col.updateOne(<DOCUMENT>, upsert()) instead of col.save(<DOCUMENT>) plus First fixed does the trick.

import org.bson.codecs.pojo.annotations.BsonId
import org.litote.kmongo.* //NEEDED! import KMongo extensions
import org.litote.kmongo.util.ObjectMappingConfiguration
import kotlin.test.Test
import kotlin.test.assertEquals
import kotlin.test.assertNotNull

class AppTest {

    data class Document(
            @BsonId val id: Int,
            val field1: String,
            val field2: String?
    )

    @Test fun testMongoBehaviours() {
        val client = KMongo.createClient() //use coroutine extension
        val database = client.getDatabase("test") //normal java driver usage
        val col = database.getCollection<Document>() //KMongo extension method
        ObjectMappingConfiguration.serializeNull = false
        col.deleteMany()
        run {
            col.updateOne(Document(1, "Hello1", null), upsert())
            val document = col.findOne(Document::id eq 1)
            assertNotNull(document)
            assertEquals("Hello1", document.field1)
            assertEquals(null, document.field2)
        }
        run {
            col.updateOne(Document(1, "Hello2", "World2"), upsert())
            val document = col.findOne(Document::id eq 1)
            assertNotNull(document)
            assertEquals("Hello2", document.field1)
            assertEquals("World2", document.field2)
        }
        run {
            col.updateOne(Document(1, "Hello3", null), upsert())
            val document = col.findOne(Document::id eq 1)
            assertNotNull(document)
            assertEquals("Hello3", document.field1)
            assertEquals("World2", document.field2) // because it was null
        }
    }
}