Don't generate a query body for NoopQuery

elastic4s-core/src/main/scala/com/sksamuel/elastic4s/requests/searches/aggs/builders/FiltersAggregationBuilder.scala

@@ -11,7 +11,7 @@ object FiltersAggregationBuilder {
 
     val filters = {
       builder.startArray("filters")
-      val filters = agg.filters.map(QueryBuilderFn.apply).map(_.string).mkString(",")
+      val filters = agg.filters.map(QueryBuilderFn.apply).map(_.string).filter(_.nonEmpty).mkString(",")
       builder.rawValue(filters)
       builder.endArray()
     }

elastic4s-core/src/test/scala/com/sksamuel/elastic4s/requests/searches/queries/NoopQueryBodyFnTest.scala

@@ -0,0 +1,13 @@
+package com.sksamuel.elastic4s.requests.searches.queries
+
+import com.sksamuel.elastic4s.ElasticDsl._
+import com.sksamuel.elastic4s.handlers.searches.queries.QueryBuilderFn
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class NoopQueryBodyFnTest extends AnyFunSuite with Matchers {
+  test("NoopQuery should not generate a query body") {
+    val q = boolQuery().should(Seq(NoopQuery))
+    QueryBuilderFn(q).string shouldBe """{"bool":{"should":[]}}"""
+  }
+}

elastic4s-handlers/src/main/scala/com/sksamuel/elastic4s/handlers/searches/queries/NoopQueryBuilderFn.scala

@@ -0,0 +1,7 @@
+package com.sksamuel.elastic4s.handlers.searches.queries
+
+import com.sksamuel.elastic4s.json.{XContentBuilder, XContentFactory}
+
+object NoopQueryBuilderFn {
+  def apply(): XContentBuilder = XContentFactory.parse("")
+}

elastic4s-handlers/src/main/scala/com/sksamuel/elastic4s/handlers/searches/queries/QueryBuilderFn.scala

@@ -44,7 +44,7 @@ object QueryBuilderFn {
     case q: MoreLikeThisQuery => MoreLikeThisQueryBuilderFn(q)
     case q: MultiMatchQuery => MultiMatchBodyFn(q)
     case q: NestedQuery => NestedQueryBodyFn(q)
-    case NoopQuery => XContentFactory.jsonBuilder()
+    case NoopQuery => NoopQueryBuilderFn()
     case q: ParentIdQuery => ParentIdQueryBodyFn(q)
     case q: PercolateQuery => PercolateQueryBodyFn(q)
     case q: PinnedQuery => PinnedQueryBuilderFn(q)

elastic4s-handlers/src/main/scala/com/sksamuel/elastic4s/handlers/searches/queries/compound/BoolQueryBuilderFn.scala

@@ -11,28 +11,28 @@ object BoolQueryBuilderFn {
 
     if (bool.must.nonEmpty) {
       builder.startArray("must")
-      val musts = bool.must.map(QueryBuilderFn.apply).map(_.string).mkString(",")
+      val musts = bool.must.map(QueryBuilderFn.apply).map(_.string).filter(_.nonEmpty).mkString(",")
       builder.rawValue(musts)
       builder.endArray()
     }
 
     if (bool.should.nonEmpty) {
       builder.startArray("should")
-      val should = bool.should.map(QueryBuilderFn.apply).map(_.string).mkString(",")
+      val should = bool.should.map(QueryBuilderFn.apply).map(_.string).filter(_.nonEmpty).mkString(",")
       builder.rawValue(should)
       builder.endArray()
     }
 
     if (bool.not.nonEmpty) {
       builder.startArray("must_not")
-      val nots = bool.not.map(QueryBuilderFn.apply).map(_.string).mkString(",")
+      val nots = bool.not.map(QueryBuilderFn.apply).map(_.string).filter(_.nonEmpty).mkString(",")
       builder.rawValue(nots)
       builder.endArray()
     }
 
     if (bool.filters.nonEmpty) {
       builder.startArray("filter")
-      val filters = bool.filters.map(QueryBuilderFn.apply).map(_.string).mkString(",")
+      val filters = bool.filters.map(QueryBuilderFn.apply).map(_.string).filter(_.nonEmpty).mkString(",")
       builder.rawValue(filters)
       builder.endArray()
     }

elastic4s-handlers/src/main/scala/com/sksamuel/elastic4s/handlers/searches/queries/compound/DisMaxQueryBodyFn.scala

@@ -2,7 +2,7 @@ package com.sksamuel.elastic4s.handlers.searches.queries.compound
 
 import com.sksamuel.elastic4s.handlers.searches.queries.QueryBuilderFn
 import com.sksamuel.elastic4s.json.{XContentBuilder, XContentFactory}
-import com.sksamuel.elastic4s.requests.searches.queries.DisMaxQuery
+import com.sksamuel.elastic4s.requests.searches.queries.{DisMaxQuery, NoopQuery}
 
 object DisMaxQueryBodyFn {
   def apply(q: DisMaxQuery): XContentBuilder = {
@@ -15,7 +15,7 @@ object DisMaxQueryBodyFn {
 
     builder.startArray("queries")
     // Workaround for bug where separator is not added with rawValues
-    q.queries.map(QueryBuilderFn.apply).foreach { query =>
+    q.queries.map(QueryBuilderFn.apply).filter(_.string.nonEmpty).foreach { query =>
       builder.rawValue(query)
     }
     builder.endArray()

elastic4s-tests/src/test/scala/com/sksamuel/elastic4s/search/queries/NoopQueryTest.scala

@@ -0,0 +1,36 @@
+package com.sksamuel.elastic4s.search.queries
+
+import scala.util.Try
+
+import com.sksamuel.elastic4s.requests.searches.queries.NoopQuery
+import com.sksamuel.elastic4s.testkit.DockerTests
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class NoopQueryTest extends AnyFlatSpec with Matchers with DockerTests {
+  Try {
+    client.execute {
+      deleteIndex("noop")
+    }.await
+  }
+
+  client.execute {
+    createIndex("noop")
+  }.await
+
+  "noop query" should "not error out when executed" in {
+    client.execute {
+      search("noop").query {
+        boolQuery().should(Seq(NoopQuery))
+      }
+    }.await.result
+  }
+
+  "it" should "not error out when executed in a sequence" in {
+    client.execute {
+      search("noop").query {
+        boolQuery().should(Seq(NoopQuery, NoopQuery))
+      }
+    }.await.result
+  }
+}