From 23d11c1cc88ee12f55a0d975ffc381066e7bf527 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@github.com>
Date: Fri, 11 Dec 2015 00:12:28 -0500
Subject: [PATCH] adjoin2 is idempotent for additions of and onto empty rows.

---
 test/Spec.hs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/Spec.hs b/test/Spec.hs
index a2b73f74b..fe70f0f39 100644
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -100,6 +100,10 @@ main = hspec $ do
         ], (Range 0 7, Range 0 1))
 
   describe "adjoin2" $ do
+    prop "is idempotent for additions of empty rows" $
+      \ () -> let empty = Row EmptyLine EmptyLine in
+        adjoin2 (adjoin2 [ empty ] empty) empty == (adjoin2 [ empty ] empty)
+
     it "appends appends HTML onto incomplete lines" $
       adjoin2 [ rightRowText "[" ] (rightRowText "a") `shouldBe`
               [ rightRow [ Text "[", Text "a" ] ]