From 92fc8b32ddb824cd69988f85488ff3013fbccd87 Mon Sep 17 00:00:00 2001
From: LMnet <lmnet89@gmail.com>
Date: Wed, 17 Apr 2019 17:04:13 +0700
Subject: [PATCH] Added collectFirst to Chain and NonEmptyChain

---
 core/src/main/scala/cats/data/Chain.scala       | 17 +++++++++++++++++
 .../main/scala/cats/data/NonEmptyChain.scala    |  6 ++++++
 2 files changed, 23 insertions(+)

diff --git a/core/src/main/scala/cats/data/Chain.scala b/core/src/main/scala/cats/data/Chain.scala
index aa229dc9ba..b4611e81f9 100644
--- a/core/src/main/scala/cats/data/Chain.scala
+++ b/core/src/main/scala/cats/data/Chain.scala
@@ -145,6 +145,23 @@ sealed abstract class Chain[+A] {
       else acc
     }
 
+  /**
+    * Finds the first element of this `Chain` for which the given partial
+    * function is defined, and applies the partial function to it.
+    */
+  final def collectFirst[B](pf: PartialFunction[A, B]): Option[B] = {
+    var result: Option[B] = None
+    foreachUntil { a =>
+      // trick from TraversableOnce, used to avoid calling both isDefined and apply (or calling lift)
+      val x = pf.applyOrElse(a, sentinel)
+      if (x.asInstanceOf[AnyRef] ne sentinel) {
+        result = Some(x.asInstanceOf[B])
+        true
+      } else false
+    }
+    result
+  }
+
   /**
    * Remove elements not matching the predicate
    */
diff --git a/core/src/main/scala/cats/data/NonEmptyChain.scala b/core/src/main/scala/cats/data/NonEmptyChain.scala
index 9aad230469..2d7eec0fe9 100644
--- a/core/src/main/scala/cats/data/NonEmptyChain.scala
+++ b/core/src/main/scala/cats/data/NonEmptyChain.scala
@@ -239,6 +239,12 @@ class NonEmptyChainOps[A](private val value: NonEmptyChain[A]) extends AnyVal {
    */
   final def collect[B](pf: PartialFunction[A, B]): Chain[B] = toChain.collect(pf)
 
+  /**
+    * Finds the first element of this `NonEmptyChain` for which the given partial
+    * function is defined, and applies the partial function to it.
+    */
+  final def collectFirst[B](pf: PartialFunction[A, B]): Option[B] = toChain.collectFirst(pf)
+
   /**
    * Filters all elements of this chain that do not satisfy the given predicate.
    */