Add addLeft/addRight for Ior

core/src/main/scala/cats/data/Ior.scala

@@ -98,6 +98,58 @@ sealed abstract class Ior[+A, +B] extends Product with Serializable {
   final def putRight[C](right: C): A Ior C =
     fold(Ior.both(_, right), _ => Ior.right(right), (a, _) => Ior.both(a, right))
 
+  /**
+   * When a Left value is present in the Ior, combine it will the value specified.
+   *
+   * When the Left value is absent, set it to the value specified.
+   *
+   * Example:
+   * {{{
+   * scala> import cats.data.Ior
+   * scala> import cats.implicits._
+   *
+   * scala> val ior1 = "abc".leftIor[Int]
+   * scala> ior1.addLeft("def")
+   * res0: Ior[String, Int] = Left(abcdef)
+   *
+   * scala> val ior2 = 123.rightIor[String]
+   * scala> ior2.addLeft("abc")
+   * res1: cats.data.Ior[String,Int] = Both(abc,123)
+   *
+   * scala> val ior3 = Ior.Both("abc",123)
+   * scala> ior3.addLeft("def")
+   * res2: Ior[String, Int] = Both(abcdef,123)
+   * }}}
+   */
+  final def addLeft[AA >: A](left: AA)(implicit AA: Semigroup[AA]): AA Ior B =
+    fold(l => Ior.left(AA.combine(l, left)), Ior.both(left, _), (l, r) => Ior.both(AA.combine(l, left), r))
+
+  /**
+   * When a Right value is present in the Ior, combine it will the value specified.
+   *
+   * When the Right value is absent, set it to the value specified.
+   *
+   * Example:
+   * {{{
+   * scala> import cats.data.Ior
+   * scala> import cats.implicits._
+   *
+   * scala> val ior1 = "abc".leftIor[Int]
+   * scala> ior1.addRight(123)
+   * res0: Ior[String, Int] = Both(abc,123)
+   *
+   * scala> val ior2 = 123.rightIor[String]
+   * scala> ior2.addRight(123)
+   * res1: Ior[String, Int] = Right(246)
+   *
+   * scala> val ior3 = Ior.Both("abc",123)
+   * scala> ior3.addRight(123)
+   * res2: Ior[String, Int] = Both(abc,246)
+   * }}}
+   */
+  final def addRight[BB >: B](right: BB)(implicit BB: Semigroup[BB]): A Ior BB =
+    fold(Ior.both(_, right), r => Ior.right(BB.combine(r, right)), (l, r) => Ior.both(l, BB.combine(r, right)))
+
   /**
    * Example:
    * {{{

tests/src/test/scala/cats/tests/IorSuite.scala

@@ -182,6 +182,32 @@ class IorSuite extends CatsSuite {
     }
   }
 
+  test("addLeft") {
+    forAll { (i: Int Ior Int, j: Int) =>
+      val expectedResult =
+        if (i.isLeft)
+          Ior.left(i.left.get + j)
+        else if (i.isRight)
+          Ior.both(j, i.right.get)
+        else
+          Ior.both(i.left.get + j, i.right.get)
+      assert(i.addLeft(j) === expectedResult)
+    }
+  }
+
+  test("addRight") {
+    forAll { (i: Int Ior Int, j: Int) =>
+      val expectedResult =
+        if (i.isLeft)
+          Ior.both(i.left.get, j)
+        else if (i.isRight)
+          Ior.right(i.right.get + j)
+        else
+          Ior.both(i.left.get, i.right.get + j)
+      assert(i.addRight(j) === expectedResult)
+    }
+  }
+
   test("combine left") {
     forAll { (i: Int Ior String, j: Int Ior String) =>
       assert(i.combine(j).left === (i.left.map(_ + j.left.getOrElse(0)).orElse(j.left)))