fix: upgrade smithy and correct formurl serialization of empty lists (#727)

Author: lucix-aws

.changes/8b692602-06c4-4c97-b554-a08cac97e1ea.json

@@ -0,0 +1,5 @@
+{
+    "id": "8b692602-06c4-4c97-b554-a08cac97e1ea",
+    "type": "bugfix",
+    "description": "Correct formurl serialization of empty lists"
+}

gradle.properties

@@ -21,7 +21,7 @@ jsoupVersion=1.14.3
 okHttpVersion=5.0.0-alpha.10
 
 # codegen
-smithyVersion=1.25.2
+smithyVersion=1.26.1
 smithyGradleVersion=0.6.0
 
 # testing/utility
@@ -43,4 +43,4 @@ kotlinLoggingVersion=2.1.21
 slf4jVersion=1.7.36
 
 # crt
-crtKotlinVersion=0.6.5
+crtKotlinVersion=0.6.5

runtime/serde/serde-form-url/common/src/aws/smithy/kotlin/runtime/serde/formurl/FormUrlSerializer.kt

@@ -157,7 +157,10 @@ private class FormUrlStructSerializer(
 
     override fun listField(descriptor: SdkFieldDescriptor, block: ListSerializer.() -> Unit) {
         val childDescriptor = descriptor.copyWithNewSerialName("${prefix}${descriptor.serialName}")
-        FormUrlListSerializer(parent, childDescriptor).apply(block)
+        FormUrlListSerializer(parent, childDescriptor).apply {
+            block()
+            endList()
+        }
     }
 
     override fun mapField(descriptor: SdkFieldDescriptor, block: MapSerializer.() -> Unit) {
@@ -179,6 +182,7 @@ private class FormUrlListSerializer(
     private val descriptor: SdkFieldDescriptor,
 ) : ListSerializer {
     private val buffer = parent.buffer
+    private val initialBufferPos = buffer.writePosition
     private var idx = 0
 
     private fun prefix(): String = when {
@@ -197,7 +201,15 @@ private class FormUrlListSerializer(
         buffer.apply(block)
     }
 
-    override fun endList() {}
+    override fun endList() {
+        if (buffer.writePosition == initialBufferPos) {
+            // explicit serialization of an empty list
+            if (buffer.writePosition > 0u) buffer.write("&")
+            buffer.write(descriptor.serialName)
+            buffer.write("=")
+        }
+    }
+
     override fun serializeBoolean(value: Boolean) = writePrefixed { write("$value") }
     override fun serializeChar(value: Char) = writePrefixed { write(value.toString()) }
     override fun serializeByte(value: Byte) = writePrefixed { commonWriteNumber(value) }
@@ -312,7 +324,10 @@ private class FormUrlMapSerializer(
         writeKey(key)
 
         val childDescriptor = SdkFieldDescriptor(SerialKind.List, FormUrlSerialName("$commonPrefix.${mapName.value}"))
-        FormUrlListSerializer(parent, childDescriptor).apply(block)
+        FormUrlListSerializer(parent, childDescriptor).apply {
+            block()
+            endList()
+        }
     }
 
     override fun mapEntry(key: String, mapDescriptor: SdkFieldDescriptor, block: MapSerializer.() -> Unit) {

runtime/serde/serde-form-url/common/test/aws/smithy/kotlin/runtime/serde/formurl/FormUrlSerializerTest.kt

@@ -600,4 +600,40 @@ class FormUrlSerializerTest {
         val actual = serializer.toByteArray().decodeToString()
         assertEquals(expected, actual)
     }
+
+    @Test
+    fun itSerializesEmptyList() {
+        val input = ListInput(
+            listOf(),
+            null,
+        )
+
+        val expected = """
+            PrimitiveList=
+        """.trimIndent().replace("\n", "")
+
+        val serializer = FormUrlSerializer()
+        input.serialize(serializer)
+        val actual = serializer.toByteArray().decodeToString()
+        assertEquals(expected, actual)
+    }
+
+    @Test
+    fun itSerializesEmptyListInMap() {
+        val input = MapInput(
+            mapOfLists = mapOf(
+                "foo" to listOf(),
+            ),
+        )
+
+        val expected = """
+            MapOfLists.entry.1.key=foo
+            &MapOfLists.entry.1.value=
+        """.trimIndent().replace("\n", "")
+
+        val serializer = FormUrlSerializer()
+        input.serialize(serializer)
+        val actual = serializer.toByteArray().decodeToString()
+        assertEquals(expected, actual)
+    }
 }