[Kotlin CR] Support naming strategy for bson-kotlinx (#209)

* add snake case serialization eg

* version note

* driver reference

* what's new

* release note

* dependency name

* bluehawk

* RR feedback

* MW feedback

---------

Co-authored-by: rustagir <[email protected]>

Author: rachel-mack

examples/src/test/kotlin/KotlinXSerializationTest.kt

@@ -26,6 +26,7 @@ import org.bson.codecs.configuration.CodecRegistries
 import org.bson.codecs.kotlinx.BsonConfiguration
 import org.bson.codecs.kotlinx.BsonDecoder
 import org.bson.codecs.kotlinx.BsonEncoder
+import org.bson.codecs.kotlinx.BsonNamingStrategy
 import org.bson.codecs.kotlinx.KotlinSerializerCodec
 import org.bson.codecs.kotlinx.ObjectIdSerializer
 import org.bson.types.ObjectId
@@ -133,6 +134,34 @@ internal class KotlinXSerializationTest {
         collection.drop()
     }
 
+    @Test
+    fun snakeCaseNamingTest() = runBlocking {
+        @Serializable
+        data class PaintOrder(
+            val ManufacturerName: String,
+            val QuantityOfCans: Int,
+        )
+
+        val collection = database.getCollection<PaintOrder>("orders2")
+
+        // :snippet-start: snake-case-naming
+        val myCustomCodec = KotlinSerializerCodec.create<PaintOrder>(
+            bsonConfiguration = BsonConfiguration(bsonNamingStrategy = BsonNamingStrategy.SNAKE_CASE)
+        )
+
+        val registry = CodecRegistries.fromRegistries(
+            CodecRegistries.fromCodecs(myCustomCodec), collection.codecRegistry
+        )
+        // :snippet-end:
+
+        val paint = PaintOrder("Acme", 10)
+        collection.withCodecRegistry(registry).insertOne(paint)
+        val result = collection.withDocumentClass<Document>().find().first().toJson()
+        assertTrue(result.contains("quantity_of_cans"))
+        assertFalse(result.contains("ManufacturerName"))
+        collection.drop()
+    }
+
     // :snippet-start: kserializer
     object InstantAsBsonDateTime : KSerializer<Instant> {
         override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("InstantAsBsonDateTime", PrimitiveKind.LONG)

source/examples/generated/KotlinXSerializationTest.snippet.snake-case-naming.kt

@@ -0,0 +1,7 @@
+val myCustomCodec = KotlinSerializerCodec.create<PaintOrder>(
+    bsonConfiguration = BsonConfiguration(bsonNamingStrategy = BsonNamingStrategy.SNAKE_CASE)
+)
+
+val registry = CodecRegistries.fromRegistries(
+    CodecRegistries.fromCodecs(myCustomCodec), collection.codecRegistry
+)

source/fundamentals/data-formats/serialization.txt

@@ -173,7 +173,8 @@ package to create a codec for your ``@Serializable`` data classes and
 customize what is stored.
 
 Use the ``BsonConfiguration`` class to define the configuration, 
-including whether to encode defaults, encode nulls, or define class discriminators.
+including whether to encode defaults, encode nulls, define class discriminators,
+or enforce snake case.
 
 To create a custom codec, install the ``bson-kotlinx``
 dependency to your project. Select from the following tabs to see how to
@@ -241,12 +242,33 @@ The following example shows how to create a codec using the
 .. literalinclude:: /examples/generated/KotlinXSerializationTest.snippet.custom-serialization.kt
     :language: kotlin
 
+.. _kotlin-serialization-snake-case-eg:
+
+Implement Snake Case Naming Strategy
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When using ``bson-kotlinx`` package v5.4 or later, you can direct the driver to
+serialize data class field names written in camel case to snake case in MongoDB.
+The following example shows how to create and register a custom codec
+to convert data class field names into snake case by setting the
+``bsonNamingStrategy`` parameter in a codec:
+
+.. code-block:: kotlin
+    :copyable: true
+
+   import org.bson.codecs.kotlinx.BsonConfiguration
+   import org.bson.codecs.kotlinx.BsonNamingStrategy
+
+.. literalinclude:: /examples/generated/KotlinXSerializationTest.snippet.snake-case-naming.kt
+   :language: kotlin
+
 For more information about the methods and classes mentioned in this section,
 see the following API documentation:
 
 - `KotlinSerializerCodec <{+api-root+}/bson-kotlinx/bson-kotlinx/org.bson.codecs.kotlinx/-kotlin-serializer-codec/index.html>`__
 - `KotlinSerializerCodec.create() <{+api-root+}/bson-kotlinx/bson-kotlinx/org.bson.codecs.kotlinx/-kotlin-serializer-codec/-companion/create.html>`__
 - `BsonConfiguration <{+api-root+}/bson-kotlinx/bson-kotlinx/org.bson.codecs.kotlinx/-bson-configuration/index.html>`__
+- `BsonNamingStrategy <{+api-root+}/bson-kotlinx/bson-kotlinx/org.bson.codecs.kotlinx/-bson-naming-strategy/index.html>`__
 
 .. _kotlin-polymorphic:
 

source/whats-new.txt

@@ -31,6 +31,10 @@ What's New in 5.4
 The 5.4 driver release includes the following changes, fixes,
 and features:
 
+- Adds ``BsonConfiguration`` support for ``bson-kotlinx`` snake case conversion
+  during serialization. To learn more, see the
+  :ref:`kotlin-serialization-snake-case-eg` section on the Serialization page.
+
 .. sharedinclude:: dbx/jvm/v5.4-wn-items.rst
 
    .. replacement:: install-bom-link