fix: Enable EC2 query empty list protocol test (#794)

* Add fix for list member serialization in EC2 query protocol.

* Update codegen test

---------

Co-authored-by: Sichan Yoo <[email protected]>
Co-authored-by: Josh Elkins <[email protected]>

Author: 3 people

smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/member/MemberShapeEncodeGenerator.kt

@@ -104,6 +104,12 @@ abstract class MemberShapeEncodeGenerator(
         val listKey = nodeInfoUtils.nodeInfo(member)
         val isFlattened = member.hasTrait<XmlFlattenedTrait>() || ctx.service.awsProtocol == AWSProtocol.EC2_QUERY
         val memberNodeInfo = nodeInfoUtils.nodeInfo(listShape.member)
+        // AWS Query protocol keeps a list member in the request even if it is empty, e.g., List=&Version=2020-01-08
+        // EC2 Query protocol leaves out a list member from the request if it is empty, e.g., Version=2020-01-08
+        if (ctx.service.awsProtocol == AWSProtocol.EC2_QUERY) {
+            writer.write("if !(\$L\$L?.isEmpty ?? true) {", prefix, memberName)
+            writer.indent()
+        }
         writer.write(
             "try writer[\$L].writeList(\$L\$L, memberWritingClosure: \$L, memberNodeInfo: \$L, isFlattened: \$L)",
             listKey,
@@ -113,6 +119,10 @@ abstract class MemberShapeEncodeGenerator(
             memberNodeInfo,
             isFlattened
         )
+        if (ctx.service.awsProtocol == AWSProtocol.EC2_QUERY) {
+            writer.dedent()
+            writer.write("}")
+        }
     }
 
     private fun writeMapMember(member: MemberShape, mapShape: MapShape, prefix: String, isSparse: Boolean) {

smithy-swift-codegen/src/test/kotlin/serde/ec2/OnlyFlattenedListEncodeFormURLGeneratorTests.kt

@@ -25,10 +25,18 @@ extension Ec2QueryListsInput {
 
     static func write(value: Ec2QueryListsInput?, to writer: SmithyFormURL.Writer) throws {
         guard let value else { return }
-        try writer["ComplexListArg"].writeList(value.complexListArg, memberWritingClosure: Ec2queryprotocolClientTypes.GreetingStruct.write(value:to:), memberNodeInfo: "Member", isFlattened: true)
-        try writer["ListArg"].writeList(value.listArg, memberWritingClosure: SmithyReadWrite.WritingClosures.writeString(value:to:), memberNodeInfo: "Member", isFlattened: true)
-        try writer["Hi"].writeList(value.listArgWithXmlName, memberWritingClosure: SmithyReadWrite.WritingClosures.writeString(value:to:), memberNodeInfo: "Item", isFlattened: true)
-        try writer["ListArgWithXmlNameMember"].writeList(value.listArgWithXmlNameMember, memberWritingClosure: SmithyReadWrite.WritingClosures.writeString(value:to:), memberNodeInfo: "Item", isFlattened: true)
+        if !(value.complexListArg?.isEmpty ?? true) {
+            try writer["ComplexListArg"].writeList(value.complexListArg, memberWritingClosure: Ec2queryprotocolClientTypes.GreetingStruct.write(value:to:), memberNodeInfo: "Member", isFlattened: true)
+        }
+        if !(value.listArg?.isEmpty ?? true) {
+            try writer["ListArg"].writeList(value.listArg, memberWritingClosure: SmithyReadWrite.WritingClosures.writeString(value:to:), memberNodeInfo: "Member", isFlattened: true)
+        }
+        if !(value.listArgWithXmlName?.isEmpty ?? true) {
+            try writer["Hi"].writeList(value.listArgWithXmlName, memberWritingClosure: SmithyReadWrite.WritingClosures.writeString(value:to:), memberNodeInfo: "Item", isFlattened: true)
+        }
+        if !(value.listArgWithXmlNameMember?.isEmpty ?? true) {
+            try writer["ListArgWithXmlNameMember"].writeList(value.listArgWithXmlNameMember, memberWritingClosure: SmithyReadWrite.WritingClosures.writeString(value:to:), memberNodeInfo: "Item", isFlattened: true)
+        }
         try writer["Action"].write("Ec2QueryLists")
         try writer["Version"].write("2020-01-08")
     }