address comments

.gitignore

@@ -6,3 +6,4 @@ out/
 *.iws
 .DS_Store
 *.log
+http

src/main/kotlin/com/amazon/opendistroforelasticsearch/indexmanagement/indexstatemanagement/model/ChangePolicy.kt

@@ -44,6 +44,14 @@ data class ChangePolicy(
     val isSafe: Boolean
 ) : Writeable, ToXContentObject {
 
+    @Throws(IOException::class)
+    constructor(sin: StreamInput) : this(
+        policyID = sin.readString(),
+        state = sin.readOptionalString(),
+        include = sin.readList(::StateFilter),
+        isSafe = sin.readBoolean()
+    )
+
     override fun toXContent(builder: XContentBuilder, params: ToXContent.Params): XContentBuilder {
         builder
             .startObject()
@@ -54,6 +62,7 @@ data class ChangePolicy(
         return builder
     }
 
+    @Throws(IOException::class)
     override fun writeTo(out: StreamOutput) {
         out.writeString(policyID)
         out.writeOptionalString(state)
@@ -68,17 +77,7 @@ data class ChangePolicy(
         const val IS_SAFE_FIELD = "is_safe"
 
         fun fromStreamInput(sin: StreamInput): ChangePolicy {
-            val policyID: String? = sin.readString()
-            val state: String? = sin.readOptionalString()
-            val isSafe: Boolean = sin.readBoolean()
-            val include: MutableList<StateFilter> = sin.readList { StateFilter.fromStreamInput(it) }
-
-            return ChangePolicy(
-                requireNotNull(policyID) { "ChangePolicy policy id is null" },
-                state,
-                include.toList(),
-                isSafe
-            )
+            return ChangePolicy(sin)
         }
 
         @JvmStatic

src/main/kotlin/com/amazon/opendistroforelasticsearch/indexmanagement/indexstatemanagement/model/StateFilter.kt

@@ -25,6 +25,12 @@ import java.io.IOException
 
 data class StateFilter(val state: String) : Writeable {
 
+    @Throws(IOException::class)
+    constructor(sin: StreamInput) : this(
+        state = String()
+    )
+
+    @Throws(IOException::class)
     override fun writeTo(out: StreamOutput) {
         out.writeString(state)
     }
@@ -51,9 +57,7 @@ data class StateFilter(val state: String) : Writeable {
         }
 
         fun fromStreamInput(sin: StreamInput): StateFilter {
-            val state: String? = sin.readString()
-
-            return StateFilter(requireNotNull(state) { "Must include a state when using include filter" })
+            return StateFilter(sin)
         }
     }
 }