Fixed: Incorrectly grabbing revision downgrades

Closes #4431

src/NzbDrone.Core.Test/DecisionEngineTests/UpgradeDiskSpecificationFixture.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using FizzWare.NBuilder;
 using FluentAssertions;
+using Moq;
 using NUnit.Framework;
 using NzbDrone.Core.DecisionEngine.Specifications;
 using NzbDrone.Core.MediaFiles;
@@ -138,5 +139,19 @@ namespace NzbDrone.Core.Test.DecisionEngineTests
             _parseResultSingle.ParsedEpisodeInfo.Quality = new QualityModel(Quality.WEBDL1080p);
             _upgradeDisk.IsSatisfiedBy(_parseResultSingle, null).Accepted.Should().BeFalse();
         }
+        
+        [Test]
+        public void should_not_be_upgradable_if_revision_downgrade_and_preferred_word_upgrade_if_propers_are_preferred()
+        {
+            Mocker.GetMock<IEpisodeFilePreferredWordCalculator>()
+                  .Setup(s => s.Calculate(It.IsAny<Series>(), It.IsAny<EpisodeFile>()))
+                  .Returns(5);
+
+            _parseResultSingle.PreferredWordScore = 10;
+
+            _firstFile.Quality = new QualityModel(Quality.WEBDL1080p, new Revision(2));
+            _parseResultSingle.ParsedEpisodeInfo.Quality = new QualityModel(Quality.WEBDL1080p);
+            _upgradeDisk.IsSatisfiedBy(_parseResultSingle, null).Accepted.Should().BeFalse();
+        }
     }
 }

src/NzbDrone.Core/DecisionEngine/Specifications/UpgradableSpecification.cs

@@ -39,6 +39,7 @@ namespace NzbDrone.Core.DecisionEngine.Specifications
         {
             var qualityComparer = new QualityModelComparer(qualityProfile);
             var qualityCompare = qualityComparer.Compare(newQuality?.Quality, currentQuality.Quality);
+            var downloadPropersAndRepacks = _configService.DownloadPropersAndRepacks;
 
             if (qualityCompare > 0)
             {
@@ -52,15 +53,25 @@ namespace NzbDrone.Core.DecisionEngine.Specifications
                 return false;
             }
 
+            var qualityRevisionComapre = newQuality?.Revision.CompareTo(currentQuality.Revision);
+
             // Accept unless the user doesn't want to prefer propers, optionally they can
             // use preferred words to prefer propers/repacks over non-propers/repacks.
-            if (_configService.DownloadPropersAndRepacks != ProperDownloadTypes.DoNotPrefer &&
-                newQuality?.Revision.CompareTo(currentQuality.Revision) > 0)
+            if (downloadPropersAndRepacks != ProperDownloadTypes.DoNotPrefer &&
+                qualityRevisionComapre > 0)
             {
                 _logger.Debug("New item has a better quality revision");
                 return true;
             }
 
+            // Reject unless the user does not prefer propers/repacks and it's a revision downgrade.
+            if (downloadPropersAndRepacks != ProperDownloadTypes.DoNotPrefer &&
+                qualityRevisionComapre < 0)
+            {
+                _logger.Debug("Existing item has a better quality revision, skipping");
+                return false;
+            }
+
             var languageCompare = new LanguageComparer(languageProfile).Compare(newLanguage, currentLanguage);
 
             if (languageCompare > 0)
@@ -77,7 +88,7 @@ namespace NzbDrone.Core.DecisionEngine.Specifications
             
             if (!IsPreferredWordUpgradable(currentScore, newScore))
             {
-                _logger.Debug("Existing item has a better preferred word score, skipping");
+                _logger.Debug("Existing item has an equal or better preferred word score, skipping");
                 return false;
             }