Enhance KotlinSerializer with value codecs for widening primitive conversion.

bson-kotlinx/src/main/kotlin/org/bson/codecs/kotlinx/BsonDecoder.kt

@@ -36,6 +36,8 @@ import org.bson.BsonType
 import org.bson.BsonValue
 import org.bson.codecs.BsonValueCodec
 import org.bson.codecs.DecoderContext
+import org.bson.internal.NumberCodecHelper
+import org.bson.internal.StringCodecHelper
 import org.bson.types.ObjectId
 
 /**
@@ -154,14 +156,17 @@ internal open class DefaultBsonDecoder(
         }
     }
 
-    override fun decodeByte(): Byte = decodeInt().toByte()
-    override fun decodeChar(): Char = decodeString().single()
-    override fun decodeFloat(): Float = decodeDouble().toFloat()
-    override fun decodeShort(): Short = decodeInt().toShort()
-    override fun decodeBoolean(): Boolean = readOrThrow({ reader.readBoolean() }, BsonType.BOOLEAN)
-    override fun decodeDouble(): Double = readOrThrow({ reader.readDouble() }, BsonType.DOUBLE)
-    override fun decodeInt(): Int = readOrThrow({ reader.readInt32() }, BsonType.INT32)
-    override fun decodeLong(): Long = readOrThrow({ reader.readInt64() }, BsonType.INT64)
+    override fun decodeByte(): Byte = NumberCodecHelper.decodeByte(reader)
+
+    override fun decodeChar(): Char = StringCodecHelper.decodeChar(reader)
+    override fun decodeFloat(): Float = NumberCodecHelper.decodeFloat(reader)
+
+    override fun decodeShort(): Short = NumberCodecHelper.decodeShort(reader)
+    override fun decodeBoolean(): Boolean = reader.readBoolean()
+
+    override fun decodeDouble(): Double = NumberCodecHelper.decodeDouble(reader)
+    override fun decodeInt(): Int = NumberCodecHelper.decodeInt(reader)
+    override fun decodeLong(): Long = NumberCodecHelper.decodeLong(reader)
     override fun decodeString(): String = readOrThrow({ reader.readString() }, BsonType.STRING)
 
     override fun decodeNull(): Nothing? {

bson-kotlinx/src/test/kotlin/org/bson/codecs/kotlinx/KotlinSerializerCodecTest.kt

@@ -15,6 +15,7 @@
  */
 package org.bson.codecs.kotlinx
 
+import java.util.stream.Stream
 import kotlin.test.assertEquals
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.MissingFieldException
@@ -23,12 +24,17 @@ import kotlinx.serialization.modules.SerializersModule
 import kotlinx.serialization.modules.plus
 import kotlinx.serialization.modules.polymorphic
 import kotlinx.serialization.modules.subclass
+import org.bson.BsonBoolean
 import org.bson.BsonDocument
 import org.bson.BsonDocumentReader
 import org.bson.BsonDocumentWriter
+import org.bson.BsonDouble
+import org.bson.BsonInt32
+import org.bson.BsonInt64
 import org.bson.BsonInvalidOperationException
 import org.bson.BsonMaxKey
 import org.bson.BsonMinKey
+import org.bson.BsonString
 import org.bson.BsonUndefined
 import org.bson.codecs.DecoderContext
 import org.bson.codecs.EncoderContext
@@ -90,11 +96,12 @@ import org.bson.codecs.kotlinx.samples.SealedInterface
 import org.bson.codecs.kotlinx.samples.ValueClass
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertThrows
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.MethodSource
 
 @OptIn(ExperimentalSerializationApi::class)
 @Suppress("LargeClass")
 class KotlinSerializerCodecTest {
-    private val numberLong = "\$numberLong"
     private val oid = "\$oid"
     private val emptyDocument = "{}"
     private val altConfiguration =
@@ -134,15 +141,59 @@ class KotlinSerializerCodecTest {
 
     private val allBsonTypesDocument = BsonDocument.parse(allBsonTypesJson)
 
-    @Test
-    fun testDataClassWithSimpleValues() {
-        val expected =
-            """{"char": "c", "byte": 0, "short": 1, "int": 22, "long": {"$numberLong": "42"}, "float": 4.0,
-                | "double": 4.2, "boolean": true, "string": "String"}"""
-                .trimMargin()
-        val dataClass = DataClassWithSimpleValues('c', 0, 1, 22, 42L, 4.0f, 4.2, true, "String")
+    companion object {
+        @JvmStatic
+        fun testTypesCastingDataClassWithSimpleValues(): Stream<BsonDocument> {
+            return Stream.of(
+                BsonDocument()
+                    .append("char", BsonString("c"))
+                    .append("byte", BsonInt32(1))
+                    .append("short", BsonInt32(2))
+                    .append("int", BsonInt32(10))
+                    .append("long", BsonInt32(10))
+                    .append("float", BsonInt32(2))
+                    .append("double", BsonInt32(3))
+                    .append("boolean", BsonBoolean.TRUE)
+                    .append("string", BsonString("String")),
+                BsonDocument()
+                    .append("char", BsonString("c"))
+                    .append("byte", BsonDouble(1.0))
+                    .append("short", BsonDouble(2.0))
+                    .append("int", BsonDouble(9.9999999999999992))
+                    .append("long", BsonDouble(9.9999999999999992))
+                    .append("float", BsonDouble(2.0))
+                    .append("double", BsonDouble(3.0))
+                    .append("boolean", BsonBoolean.TRUE)
+                    .append("string", BsonString("String")),
+                BsonDocument()
+                    .append("char", BsonString("c"))
+                    .append("byte", BsonDouble(1.0))
+                    .append("short", BsonDouble(2.0))
+                    .append("int", BsonDouble(10.0))
+                    .append("long", BsonDouble(10.0))
+                    .append("float", BsonDouble(2.0))
+                    .append("double", BsonDouble(3.0))
+                    .append("boolean", BsonBoolean.TRUE)
+                    .append("string", BsonString("String")),
+                BsonDocument()
+                    .append("char", BsonString("c"))
+                    .append("byte", BsonInt64(1))
+                    .append("short", BsonInt64(2))
+                    .append("int", BsonInt64(10))
+                    .append("long", BsonInt64(10))
+                    .append("float", BsonInt64(2))
+                    .append("double", BsonInt64(3))
+                    .append("boolean", BsonBoolean.TRUE)
+                    .append("string", BsonString("String")))
+        }
+    }
 
-        assertRoundTrips(expected, dataClass)
+    @ParameterizedTest
+    @MethodSource("testTypesCastingDataClassWithSimpleValues")
+    fun testTypesCastingDataClassWithSimpleValues(data: BsonDocument) {
+        val expectedDataClass = DataClassWithSimpleValues('c', 1, 2, 10, 10L, 2.0f, 3.0, true, "String")
+
+        assertDecodesTo(data, expectedDataClass)
     }
 
     @Test

bson/src/main/org/bson/codecs/AtomicIntegerCodec.java

@@ -21,7 +21,7 @@
 
 import java.util.concurrent.atomic.AtomicInteger;
 
-import static org.bson.codecs.NumberCodecHelper.decodeInt;
+import static org.bson.internal.NumberCodecHelper.decodeInt;
 
 /**
  * Encodes and decodes {@code AtomicInteger} objects.

bson/src/main/org/bson/codecs/AtomicLongCodec.java

@@ -21,7 +21,7 @@
 
 import java.util.concurrent.atomic.AtomicLong;
 
-import static org.bson.codecs.NumberCodecHelper.decodeLong;
+import static org.bson.internal.NumberCodecHelper.decodeLong;
 
 /**
  * Encodes and decodes {@code AtomicLong} objects.

bson/src/main/org/bson/codecs/ByteCodec.java

@@ -16,12 +16,10 @@
 
 package org.bson.codecs;
 
-import org.bson.BsonInvalidOperationException;
 import org.bson.BsonReader;
 import org.bson.BsonWriter;
 
-import static java.lang.String.format;
-import static org.bson.codecs.NumberCodecHelper.decodeInt;
+import static org.bson.internal.NumberCodecHelper.decodeByte;
 
 /**
  * Encodes and decodes {@code Byte} objects.
@@ -37,11 +35,7 @@ public void encode(final BsonWriter writer, final Byte value, final EncoderConte
 
     @Override
     public Byte decode(final BsonReader reader, final DecoderContext decoderContext) {
-        int value = decodeInt(reader);
-        if (value < Byte.MIN_VALUE || value > Byte.MAX_VALUE) {
-            throw new BsonInvalidOperationException(format("%s can not be converted into a Byte.", value));
-        }
-        return (byte) value;
+        return decodeByte(reader);
     }
 
     @Override

bson/src/main/org/bson/codecs/CharacterCodec.java

@@ -16,11 +16,10 @@
 
 package org.bson.codecs;
 
-import org.bson.BsonInvalidOperationException;
 import org.bson.BsonReader;
 import org.bson.BsonWriter;
+import org.bson.internal.StringCodecHelper;
 
-import static java.lang.String.format;
 import static org.bson.assertions.Assertions.notNull;
 
 /**
@@ -38,13 +37,7 @@ public void encode(final BsonWriter writer, final Character value, final Encoder
 
     @Override
     public Character decode(final BsonReader reader, final DecoderContext decoderContext) {
-        String string = reader.readString();
-        if (string.length() != 1) {
-            throw new BsonInvalidOperationException(format("Attempting to decode the string '%s' to a character, but its length is not "
-                                                           + "equal to one", string));
-        }
-
-        return string.charAt(0);
+        return StringCodecHelper.decodeChar(reader);
     }
 
     @Override

bson/src/main/org/bson/codecs/DoubleCodec.java

@@ -19,7 +19,7 @@
 import org.bson.BsonReader;
 import org.bson.BsonWriter;
 
-import static org.bson.codecs.NumberCodecHelper.decodeDouble;
+import static org.bson.internal.NumberCodecHelper.decodeDouble;
 
 /**
  * Encodes and decodes {@code Double} objects.

bson/src/main/org/bson/codecs/FloatCodec.java

@@ -16,12 +16,10 @@
 
 package org.bson.codecs;
 
-import org.bson.BsonInvalidOperationException;
 import org.bson.BsonReader;
 import org.bson.BsonWriter;
 
-import static java.lang.String.format;
-import static org.bson.codecs.NumberCodecHelper.decodeDouble;
+import static org.bson.internal.NumberCodecHelper.decodeFloat;
 
 /**
  * Encodes and decodes {@code Float} objects.
@@ -37,11 +35,7 @@ public void encode(final BsonWriter writer, final Float value, final EncoderCont
 
     @Override
     public Float decode(final BsonReader reader, final DecoderContext decoderContext) {
-        double value = decodeDouble(reader);
-        if (value < -Float.MAX_VALUE || value > Float.MAX_VALUE) {
-            throw new BsonInvalidOperationException(format("%s can not be converted into a Float.", value));
-        }
-        return (float) value;
+        return decodeFloat(reader);
     }
 
     @Override

bson/src/main/org/bson/codecs/IntegerCodec.java

@@ -19,7 +19,7 @@
 import org.bson.BsonReader;
 import org.bson.BsonWriter;
 
-import static org.bson.codecs.NumberCodecHelper.decodeInt;
+import static org.bson.internal.NumberCodecHelper.decodeInt;
 
 /**
  * Encodes and decodes {@code Integer} objects.

bson/src/main/org/bson/codecs/LongCodec.java

@@ -19,7 +19,7 @@
 import org.bson.BsonReader;
 import org.bson.BsonWriter;
 
-import static org.bson.codecs.NumberCodecHelper.decodeLong;
+import static org.bson.internal.NumberCodecHelper.decodeLong;
 
 /**
  * Encodes and decodes {@code Long} objects.

bson/src/main/org/bson/codecs/ShortCodec.java

@@ -16,12 +16,10 @@
 
 package org.bson.codecs;
 
-import org.bson.BsonInvalidOperationException;
 import org.bson.BsonReader;
 import org.bson.BsonWriter;
 
-import static java.lang.String.format;
-import static org.bson.codecs.NumberCodecHelper.decodeInt;
+import static org.bson.internal.NumberCodecHelper.decodeShort;
 
 /**
  * Encodes and decodes {@code Short} objects.
@@ -37,11 +35,7 @@ public void encode(final BsonWriter writer, final Short value, final EncoderCont
 
     @Override
     public Short decode(final BsonReader reader, final DecoderContext decoderContext) {
-        int value = decodeInt(reader);
-        if (value < Short.MIN_VALUE || value > Short.MAX_VALUE) {
-            throw new BsonInvalidOperationException(format("%s can not be converted into a Short.", value));
-        }
-        return (short) value;
+        return decodeShort(reader);
     }
 
     @Override

bson/src/main/org/bson/codecs/NumberCodecHelper.java → bson/src/main/org/bson/internal/NumberCodecHelper.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.bson.codecs;
+package org.bson.internal;
 
 import org.bson.BsonInvalidOperationException;
 import org.bson.BsonReader;
@@ -25,9 +25,28 @@
 
 import static java.lang.String.format;
 
-final class NumberCodecHelper {
+/**
+ * This class is not part of the public API. It may be removed or changed at any time.
+ */
+public final class NumberCodecHelper {
+
+    public static byte decodeByte(final BsonReader reader) {
+        int value = decodeInt(reader);
+        if (value < Byte.MIN_VALUE || value > Byte.MAX_VALUE) {
+            throw new BsonInvalidOperationException(format("%s can not be converted into a Byte.", value));
+        }
+        return (byte) value;
+    }
+
+    public static short decodeShort(final BsonReader reader) {
+        int value = decodeInt(reader);
+        if (value < Short.MIN_VALUE || value > Short.MAX_VALUE) {
+            throw new BsonInvalidOperationException(format("%s can not be converted into a Short.", value));
+        }
+        return (short) value;
+    }
 
-    static int decodeInt(final BsonReader reader) {
+    public static int decodeInt(final BsonReader reader) {
         int intValue;
         BsonType bsonType = reader.getCurrentBsonType();
         switch (bsonType) {
@@ -61,7 +80,7 @@ static int decodeInt(final BsonReader reader) {
         return intValue;
     }
 
-    static long decodeLong(final BsonReader reader) {
+    public static long decodeLong(final BsonReader reader) {
         long longValue;
         BsonType bsonType = reader.getCurrentBsonType();
         switch (bsonType) {
@@ -91,7 +110,15 @@ static long decodeLong(final BsonReader reader) {
         return longValue;
     }
 
-    static double decodeDouble(final BsonReader reader) {
+    public static float decodeFloat(final BsonReader reader) {
+        double value = decodeDouble(reader);
+        if (value < -Float.MAX_VALUE || value > Float.MAX_VALUE) {
+            throw new BsonInvalidOperationException(format("%s can not be converted into a Float.", value));
+        }
+        return (float) value;
+    }
+
+   public static double decodeDouble(final BsonReader reader) {
         double doubleValue;
         BsonType bsonType = reader.getCurrentBsonType();
         switch (bsonType) {