Add Foldable extension collectFirstSomeM

core/src/main/scala/cats/syntax/all.scala

@@ -72,3 +72,4 @@ trait AllSyntaxBinCompat1
 
 trait AllSyntaxBinCompat2
   extends ParallelTraverseSyntax
+    with FoldableExtensionSyntax

core/src/main/scala/cats/syntax/foldable.scala

@@ -1,6 +1,8 @@
 package cats
 package syntax
 
+import cats.data.OptionT
+
 trait FoldableSyntax extends Foldable.ToFoldableOps with UnorderedFoldable.ToUnorderedFoldableOps {
   implicit final def catsSyntaxNestedFoldable[F[_]: Foldable, G[_], A](fga: F[G[A]]): NestedFoldableOps[F, G, A] =
     new NestedFoldableOps[F, G, A](fga)
@@ -93,3 +95,15 @@ final class FoldableOps[F[_], A](val fa: F[A]) extends AnyVal {
     } + suffix
   }
 }
+
+trait FoldableExtensionSyntax {
+  implicit final def catsSyntaxFoldableExtension[F[_], A](fa: F[A]): FoldableExtension[F, A] =
+    new FoldableExtension(fa)
+}
+
+final class FoldableExtension[F[_], A](val fa: F[A]) extends AnyVal {
+  def collectFirstSomeM[G[_], B](f: A => G[Option[B]])(implicit F: Foldable[F], G: Monad[G]): G[Option[B]] =
+    F.foldRight(fa, Eval.now(OptionT.none[G, B]))((a, lb) =>
+      Eval.now(OptionT(f(a)).orElse(lb.value))
+    ).value.value
+}

core/src/main/scala/cats/syntax/package.scala

@@ -26,7 +26,7 @@ package object syntax {
   object either extends EitherSyntax
   object eq extends EqSyntax
   object flatMap extends FlatMapSyntax
-  object foldable extends FoldableSyntax
+  object foldable extends FoldableSyntax with FoldableExtensionSyntax
   object functor extends FunctorSyntax
   object group extends GroupSyntax
   object invariant extends InvariantSyntax

tests/src/test/scala/cats/tests/FoldableSuite.scala

@@ -140,12 +140,20 @@ abstract class FoldableSuite[F[_]: Foldable](name: String)(
       fa.toList should === (iterator(fa).toList)
     }
   }
-  
+
   test(s"Foldable[$name] mkString_") {
     forAll { (fa: F[Int]) =>
       fa.mkString_("L[", ";", "]") should === (fa.toList.mkString("L[", ";", "]"))
     }
   }
+
+  test(s"Foldable[$name].collectFirstSomeM") {
+    forAll { (fa: F[Int], n: Int) =>
+      fa.collectFirstSomeM(x => (x > n).guard[Option].as(x).asRight[String]) should === (fa.toList.collectFirst {
+        case x if x > n => x
+      }.asRight[String])
+    }
+  }
 }
 
 class FoldableSuiteAdditional extends CatsSuite {