Fixed: Refreshing series that have duplicate season information

src/NzbDrone.Core.Test/TvTests/RefreshSeriesServiceFixture.cs

@@ -135,5 +135,50 @@ namespace NzbDrone.Core.Test.TvTests
 
             ExceptionVerification.ExpectedWarns(1);
         }
+
+        [Test]
+        public void should_not_throw_if_duplicate_season_is_in_existing_info()
+        {
+            var newSeriesInfo = _series.JsonClone();
+            newSeriesInfo.Seasons.Add(Builder<Season>.CreateNew()
+                                         .With(s => s.SeasonNumber = 2)
+                                         .Build());
+
+            _series.Seasons.Add(Builder<Season>.CreateNew()
+                                         .With(s => s.SeasonNumber = 2)
+                                         .Build());
+
+            _series.Seasons.Add(Builder<Season>.CreateNew()
+                                         .With(s => s.SeasonNumber = 2)
+                                         .Build());
+
+            GivenNewSeriesInfo(newSeriesInfo);
+
+            Subject.Execute(new RefreshSeriesCommand(_series.Id));
+
+            Mocker.GetMock<ISeriesService>()
+                  .Verify(v => v.UpdateSeries(It.Is<Series>(s => s.Seasons.Count == 2)));
+        }
+
+        [Test]
+        public void should_filter_duplicate_seasons()
+        {
+            var newSeriesInfo = _series.JsonClone();
+            newSeriesInfo.Seasons.Add(Builder<Season>.CreateNew()
+                                         .With(s => s.SeasonNumber = 2)
+                                         .Build());
+
+            newSeriesInfo.Seasons.Add(Builder<Season>.CreateNew()
+                                         .With(s => s.SeasonNumber = 2)
+                                         .Build());
+
+            GivenNewSeriesInfo(newSeriesInfo);
+
+            Subject.Execute(new RefreshSeriesCommand(_series.Id));
+
+            Mocker.GetMock<ISeriesService>()
+                  .Verify(v => v.UpdateSeries(It.Is<Series>(s => s.Seasons.Count == 2)));
+
+        }
     }
 }

src/NzbDrone.Core/Tv/RefreshSeriesService.cs

@@ -116,9 +116,11 @@ namespace NzbDrone.Core.Tv
 
         private List<Season> UpdateSeasons(Series series, Series seriesInfo)
         {
-            foreach (var season in seriesInfo.Seasons)
+            var seasons = seriesInfo.Seasons.DistinctBy(s => s.SeasonNumber).ToList();
+
+            foreach (var season in seasons)
             {
-                var existingSeason = series.Seasons.SingleOrDefault(s => s.SeasonNumber == season.SeasonNumber);
+                var existingSeason = series.Seasons.FirstOrDefault(s => s.SeasonNumber == season.SeasonNumber);
 
                 //Todo: Should this should use the previous season's monitored state?
                 if (existingSeason == null)
@@ -139,7 +141,7 @@ namespace NzbDrone.Core.Tv
                 }
             }
 
-            return seriesInfo.Seasons;
+            return seasons;
         }
 
         public void Execute(RefreshSeriesCommand message)