Fix incorrect behaviour of DefaultCodec

Author: LukynkaCZE

gradle.properties

@@ -1,2 +1,2 @@
 kotlin.code.style=official
-tide.version=3.6
+tide.version=3.7

src/main/kotlin/io/github/dockyardmc/tide/codec/DefaultCodec.kt

@@ -5,7 +5,8 @@ import io.github.dockyardmc.tide.transcoder.Transcoder
 class DefaultCodec<T>(val inner: Codec<T>, val default: T) : Codec<T> {
 
     override fun <D> encode(transcoder: Transcoder<D>, value: T): D {
-        return inner.encode(transcoder, value ?: default)
+        if (value == null || value == default) return transcoder.encodeNull()
+        return inner.encode(transcoder, value)
     }
 
     override fun <D> decode(transcoder: Transcoder<D>, value: D): T {

src/test/kotlin/io/github/dockyardmc/tide/DefaultCodecTest.kt

@@ -0,0 +1,28 @@
+package io.github.dockyardmc.tide
+
+import io.github.dockyardmc.tide.codec.Codec
+import io.github.dockyardmc.tide.codec.StructCodec
+import io.github.dockyardmc.tide.transcoder.JsonTranscoder
+import org.junit.jupiter.api.Test
+
+class DefaultCodecTest {
+
+    data class Player(val username: String, val isGay: Boolean) {
+        companion object {
+            val CODEC = StructCodec.of(
+                "username", Codec.STRING, Player::username,
+                "is_gay", Codec.BOOLEAN.default(false), Player::isGay,
+                ::Player
+            )
+        }
+    }
+
+    @Test
+    fun testDefault() {
+        val player = Player("LukynkaCZE", false)
+        val encoded = Player.CODEC.encode(JsonTranscoder, player)
+
+        assert(!encoded.toString().contains("isGay"))
+    }
+
+}