Cherry-pick "Fix stack overflow in typedPipeMonoid.zero" (#1688)

* Fix stack overflow in typedPipeMonoid.zero * Timur's comments.
twitter · May 22, 2017 · 6bcb169 · 6bcb169
1 parent 9da38a1
commit 6bcb169
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diff --git a/.gitignore b/.gitignore
@@ -37,4 +37,5 @@ scalding-hadoop-test/NOTICE
 NOTICE
 
 # Auto-copied by sbt-microsites
-docs/src/main/tut/contributing.md
+docs/src/main/tut/contributing.md
+.DS_Store
diff --git a/scalding-core/src/main/scala/com/twitter/scalding/typed/TypedPipe.scala b/scalding-core/src/main/scala/com/twitter/scalding/typed/TypedPipe.scala
@@ -102,7 +102,7 @@ object TypedPipe extends Serializable {
    * TypedPipe instances are monoids. They are isomorphic to multisets.
    */
   implicit def typedPipeMonoid[T]: Monoid[TypedPipe[T]] = new Monoid[TypedPipe[T]] {
-    def zero = empty
+    def zero = TypedPipe.empty
     def plus(left: TypedPipe[T], right: TypedPipe[T]): TypedPipe[T] =
       left ++ right
   }

diff --git a/scalding-core/src/test/scala/com/twitter/scalding/TypedPipeTest.scala b/scalding-core/src/test/scala/com/twitter/scalding/TypedPipeTest.scala
@@ -17,6 +17,7 @@ package com.twitter.scalding
 
 import org.scalatest.{ FunSuite, Matchers, WordSpec }
 
+import com.twitter.algebird.Monoid
 import com.twitter.scalding.source.TypedText
 // Use the scalacheck generators
 import org.scalacheck.Gen
@@ -121,6 +122,15 @@ class TypedSumByKeyTest extends WordSpec with Matchers {
   }
 }
 
+class TypedPipeMonoidTest extends WordSpec with Matchers {
+  "typedPipeMonoid.zero" should {
+    "be equal to TypePipe.empty" in {
+      val mon = implicitly[Monoid[TypedPipe[Int]]]
+      assert(mon.zero == TypedPipe.empty)
+    }
+  }
+}
+
 class TypedPipeSortByJob(args: Args) extends Job(args) {
   TypedPipe.from(TypedText.tsv[(Int, Float, String)]("input"))
     .groupBy(_._1)