Added parFlatMapN

project/Boilerplate.scala

@@ -349,6 +349,9 @@ object Boilerplate {
         -  /** @group ParMapArity */
         -  def parMap$arity[M[_], ${`A..N`}, Z]($fparams)(f: (${`A..N`}) => Z)(implicit p: NonEmptyParallel[M]): M[Z] =
         -    p.flatMap.map(${nestedExpansion.products}) { case ${nestedExpansion.`(a..n)`} => f(${`a..n`}) }
+        -
+        -  def flatParMap$arity[M[_], ${`A..N`}, Z]($fparams)(f: (${`A..N`}) => M[Z])(implicit p: NonEmptyParallel[M]): M[Z] =
+        -    p.flatMap.flatMap(${nestedExpansion.products}) { case ${nestedExpansion.`(a..n)`} => f(${`a..n`}) }
       |}
       """
     }
@@ -472,6 +475,12 @@ object Boilerplate {
         else
           s"def parMapN[Z](f: (${`A..N`}) => Z)(implicit p: NonEmptyParallel[M]): M[Z] = Parallel.parMap$arity($tupleArgs)(f)"
 
+      val flatParMap =
+        if (arity == 1)
+          s"def flatParMap[Z](f: (${`A..N`}) => M[Z])(implicit p: NonEmptyParallel[M]): M[Z] = p.flatMap.flatMap($tupleArgs)(f)"
+        else
+          s"def flatParMapN[Z](f: (${`A..N`}) => M[Z])(implicit p: NonEmptyParallel[M]): M[Z] = p.flatMap.flatten(Parallel.parMap$arity($tupleArgs)(f))"
+
       val parTupled =
         if (arity == 1) ""
         else
@@ -490,6 +499,7 @@ object Boilerplate {
          -private[syntax] final class Tuple${arity}ParallelOps[M[_], ${`A..N`}](private val $tupleTpe) extends Serializable {
          -  $parMap
          -  $parTupled
+         -  $flatParMap
          -}
       |
       """

tests/shared/src/test/scala/cats/tests/SyntaxSuite.scala

@@ -246,9 +246,18 @@ object SyntaxSuite {
     val fb = mock[M[B]]
     val fc = mock[M[C]]
     val f = mock[(A, B, C) => Z]
+    val mf = mock[(A, B, C) => M[Z]]
 
     tfabc.parMapN(f)
     (fa, fb, fc).parMapN(f)
+
+    tfabc.flatParMapN(mf)
+    (fa, fb, fc).flatParMapN(mf)
+
+    val tfa = mock[Tuple1[M[A]]]
+    val mfone = mock[A => M[Z]]
+
+    tfa.flatParMap(mfone)
   }
 
   def testParallelBi[M[_], F[_], T[_, _]: Bitraverse, A, B, C, D](implicit P: Parallel.Aux[M, F]): Unit = {