Feature flag to show reduced version list on package details page (#10506)

* Feature flag

Author: agr

src/AccountDeleter/EmptyFeatureFlagService.cs

@@ -358,5 +358,10 @@ public bool IsMcpServerPackageDisplayEnabled()
         {
             throw new NotImplementedException();
         }
+
+        public bool IsReducedVersionListsEnabled()
+        {
+            throw new NotImplementedException();
+        }
     }
 }

src/GitHubVulnerabilities2Db/Fakes/FakeFeatureFlagService.cs

@@ -359,5 +359,10 @@ public bool IsMcpServerPackageDisplayEnabled()
         {
             throw new NotImplementedException();
         }
+
+        public bool IsReducedVersionListsEnabled()
+        {
+            throw new NotImplementedException();
+        }
     }
 }

src/NuGetGallery.Services/Configuration/FeatureFlagService.cs

@@ -71,6 +71,7 @@ public class FeatureFlagService : IFeatureFlagService
         private const string McpServerPackageFilteringFeatureName = GalleryPrefix + "McpServerPackageFiltering";
         private const string McpServerPackageDisplayFeatureName = GalleryPrefix + "McpServerPackageDisplay";
         private const string EnableApiKeyV5ForOIDCFeatureName = GalleryPrefix + "EnableApiKeyV5ForOIDC";
+        private const string ReducedVersionLists = GalleryPrefix + "ReducedVersionLists";
 
         private const string ODataV1GetAllNonHijackedFeatureName = GalleryPrefix + "ODataV1GetAllNonHijacked";
         private const string ODataV1GetAllCountNonHijackedFeatureName = GalleryPrefix + "ODataV1GetAllCountNonHijacked";
@@ -421,7 +422,8 @@ public bool IsNuGetAccountPasswordLoginEnabled()
             return _client.IsEnabled(NuGetAccountPasswordLoginFeatureName, defaultValue: true);
         }
 
-        public bool IsFrameworkFilteringEnabled(User user) {
+        public bool IsFrameworkFilteringEnabled(User user)
+        {
             return _client.IsEnabled(FrameworkFilteringFeatureName, user, defaultValue: false);
         }
 
@@ -464,5 +466,10 @@ public bool IsMcpServerPackageDisplayEnabled()
         {
             return _client.IsEnabled(McpServerPackageDisplayFeatureName, defaultValue: false);
         }
+
+        public bool IsReducedVersionListsEnabled()
+        {
+            return _client.IsEnabled(ReducedVersionLists, defaultValue: false);
+        }
     }
 }

src/NuGetGallery.Services/Configuration/IFeatureFlagService.cs

@@ -376,5 +376,10 @@ public interface IFeatureFlagService
         bool IsMcpServerPackageFilteringEnabled();
 
         bool IsMcpServerPackageDisplayEnabled();
+
+        /// <summary>
+        /// when enabled, the package details page shows short version lists.
+        /// </summary>
+        bool IsReducedVersionListsEnabled();
     }
 }

src/NuGetGallery.Services/PackageManagement/IPackageService.cs

@@ -55,6 +55,25 @@ IReadOnlyCollection<Package> FindPackagesById(
             bool includeDeprecations,
             bool includeSupportedFrameworks);
 
+        /// <summary>
+        /// Returns <paramref name="maxCount"/> latest (by Created) versions of packages with an <see cref="Package.Id"/> of <paramref name="id"/>.
+        /// The list always includes the <paramref name="includeVersion"/> version if specified.
+        /// </summary>
+        /// <param name="id"></param>
+        /// <param name="includeVersion"></param>
+        /// <param name="includePackageRegistration"></param>
+        /// <param name="includeDeprecations"></param>
+        /// <param name="includeSupportedFrameworks"></param>
+        /// <param name="maxCount"></param>
+        /// <returns></returns>
+        IReadOnlyCollection<Package> FindLatestVersionsById(
+            string id,
+            string includeVersion,
+            bool includePackageRegistration,
+            bool includeDeprecations,
+            bool includeSupportedFrameworks,
+            int maxCount);
+
         /// <summary>
         /// Gets the package with the given ID and version when exists;
         /// otherwise gets the latest package version for the given package ID matching the provided constraints.

src/NuGetGallery.Services/PackageManagement/PackageService.cs

@@ -275,6 +275,64 @@ public IReadOnlyCollection<Package> FindPackagesById(
             return packages.ToList();
         }
 
+        public IReadOnlyCollection<Package> FindLatestVersionsById(
+            string id,
+            string includeVersion,
+            bool includePackageRegistration,
+            bool includeDeprecations,
+            bool includeSupportedFrameworks,
+            int maxCount)
+        {
+            if (id == null)
+            {
+                throw new ArgumentNullException(nameof(id));
+            }
+
+            if (maxCount < 1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(maxCount), "Max count must be greater than 0.");
+            }
+
+            var packages = GetPackagesByIdQueryable(
+                id,
+                includeLicenseReports: false,
+                includePackageRegistration: includePackageRegistration,
+                includeUser: false,
+                includeSymbolPackages: false,
+                includeDeprecations: includeDeprecations,
+                includeDeprecationRelationships: false,
+                includeSupportedFrameworks: includeSupportedFrameworks)
+                .OrderByDescending(p => p.Created)
+                .Take(maxCount)
+                .ToList();
+
+            if (!string.IsNullOrWhiteSpace(includeVersion) && !packages.Any(p => p.NormalizedVersion == includeVersion))
+            {
+                var requiredPackage = GetPackagesByIdQueryable(
+                    id,
+                    includeLicenseReports: false,
+                    includePackageRegistration: includePackageRegistration,
+                    includeUser: false,
+                    includeSymbolPackages: false,
+                    includeDeprecations: includeDeprecations,
+                    includeDeprecationRelationships: false,
+                    includeSupportedFrameworks: includeSupportedFrameworks)
+                    .Where(p => p.NormalizedVersion == includeVersion)
+                    .SingleOrDefault();
+
+                if (requiredPackage is not null)
+                {
+                    if (packages.Count >= maxCount)
+                    {
+                        packages.RemoveAt(packages.Count - 1);
+                    }
+                    packages.Add(requiredPackage);
+                }
+            }
+
+            return packages;
+        }
+
         public virtual Package FindPackageByIdAndVersion(
             string id,
             string version,

src/NuGetGallery/Controllers/PackagesController.cs

@@ -926,11 +926,25 @@ public virtual async Task<ActionResult> DisplayPackage(string id, string version
                 return RedirectToActionPermanent("DisplayPackage", new { id = id, version = normalized });
             }
 
-            // Load all packages with the ID.
-            var allVersions = _packageService.FindPackagesById(id,
-                includePackageRegistration: true,
-                includeDeprecations: true,
-                includeSupportedFrameworks: true);
+            IReadOnlyCollection<Package> allVersions;
+
+            if (_featureFlagService.IsReducedVersionListsEnabled())
+            {
+                allVersions = _packageService.FindLatestVersionsById(id,
+                    includeVersion: normalized,
+                    includePackageRegistration: true,
+                    includeDeprecations: true,
+                    includeSupportedFrameworks: true,
+                    maxCount: 20);
+            }
+            else
+            {
+                // Load all packages with the ID.
+                allVersions = _packageService.FindPackagesById(id,
+                    includePackageRegistration: true,
+                    includeDeprecations: true,
+                    includeSupportedFrameworks: true);
+            }
 
             var filterContext = new PackageFilterContext(RouteData?.Route, version);
             var package = _packageFilter.GetFiltered(allVersions, filterContext);

src/VerifyMicrosoftPackage/Fakes/FakeFeatureFlagService.cs

@@ -149,5 +149,7 @@ public class FakeFeatureFlagService : IFeatureFlagService
         public bool IsMcpServerPackageFilteringEnabled() => throw new NotImplementedException();
 
         public bool IsMcpServerPackageDisplayEnabled() => throw new NotImplementedException();
+
+        public bool IsReducedVersionListsEnabled() => throw new NotImplementedException();
     }
 }

tests/NuGetGallery.Facts/Controllers/PackagesControllerFacts.cs

@@ -241,6 +241,9 @@ private static PackagesController CreateController(
             {
                 featureFlagService = new Mock<IFeatureFlagService>();
                 featureFlagService.SetReturnsDefault<bool>(true);
+                featureFlagService
+                    .Setup(ff => ff.IsReducedVersionListsEnabled())
+                    .Returns(false);
             }
 
             renameService = renameService ?? new Mock<IPackageRenameService>();
@@ -538,6 +541,30 @@ public async Task IsIndexCheckOnlyHappensForRecentlyChangedPackages(DateTime cre
                 searchService.Verify(x => x.RawSearch(It.IsAny<SearchFilter>()), Times.Exactly(searchTimes));
             }
 
+            [Fact]
+            public async Task UsesFindLatestVersionsWhenFeatureFlagIsEnabled()
+            {
+                var featureFlagServiceMock = new Mock<IFeatureFlagService>();
+                featureFlagServiceMock
+                    .Setup(ff => ff.IsReducedVersionListsEnabled())
+                    .Returns(true);
+
+                var packageService = new Mock<IPackageService>();
+
+                var controller = CreateController(
+                    GetConfigurationService(),
+                    packageService: packageService,
+                    featureFlagService: featureFlagServiceMock);
+
+                await controller.DisplayPackage("TestPackage", "0.1.2");
+
+                packageService
+                    .Verify(ps => ps.FindLatestVersionsById("TestPackage", "0.1.2", It.IsAny<bool>(), It.IsAny<bool>(), It.IsAny<bool>(), It.IsAny<int>()), Times.Once);
+
+                packageService
+                    .Verify(ps => ps.FindPackagesById(It.IsAny<string>(), It.IsAny<bool>(), It.IsAny<bool>(), It.IsAny<bool>()), Times.Never);
+            }
+
             [Fact]
             public async Task GivenANonNormalizedVersionIt302sToTheNormalizedVersion()
             {