When a package is unlisted, return the package's published date as 1900

This ports commit 2011cd4 from the 3.x release.
Fix NuGet/NuGetGallery#4020

src/NuGet.Server/DataServices/PackageExtensions.cs

@@ -11,6 +11,8 @@ namespace NuGet.Server.DataServices
 {
     public static class PackageExtensions
     {
+        private static readonly DateTime PublishedForUnlisted = new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+
         public static ODataPackage AsODataPackage(this IPackage package, ClientCompatibility compatibility)
         {
             var serverPackage = package as ServerPackage;
@@ -19,7 +21,7 @@ public static ODataPackage AsODataPackage(this IPackage package, ClientCompatibi
                 return AsODataPackage(serverPackage, compatibility);
             }
 
-            var utcNow = DateTime.UtcNow;
+            var published = package.Published.HasValue ? package.Published.Value.UtcDateTime : DateTime.UtcNow;
 
             return new ODataPackage
             {
@@ -39,8 +41,8 @@ public static ODataPackage AsODataPackage(this IPackage package, ClientCompatibi
                 Description = package.Description,
                 Summary = package.Summary,
                 ReleaseNotes = package.ReleaseNotes,
-                Published = package.Published.HasValue ? package.Published.Value.UtcDateTime : utcNow,
-                LastUpdated = package.Published.HasValue ? package.Published.Value.UtcDateTime : utcNow,
+                Published = package.Listed ? published : PublishedForUnlisted,
+                LastUpdated = published,
                 Dependencies = string.Join("|", package.DependencySets.SelectMany(ConvertDependencySetToStrings)),
                 PackageHash = package.GetHash(Constants.HashAlgorithm),
                 PackageHashAlgorithm = Constants.HashAlgorithm,
@@ -76,7 +78,7 @@ public static ODataPackage AsODataPackage(this ServerPackage package, ClientComp
                 Description = package.Description,
                 Summary = package.Summary,
                 ReleaseNotes = package.ReleaseNotes,
-                Published = package.Created.UtcDateTime,
+                Published = package.Listed ? package.Created.UtcDateTime : PublishedForUnlisted,
                 LastUpdated = package.LastUpdated.UtcDateTime,
                 Dependencies = string.Join("|", package.DependencySets.SelectMany(ConvertDependencySetToStrings)),
                 PackageHash = package.PackageHash,

test/NuGet.Server.Tests/PackageExtensionsTest.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information. 
 
+using System;
 using System.Linq;
 using NuGet.Server.DataServices;
 using NuGet.Server.Infrastructure;
@@ -10,6 +11,52 @@ namespace NuGet.Server.Tests
 {
     public class PackageExtensionsTest
     {
+        [Fact]
+        public void AsODataPackage_Uses1900ForUnlistedPublished()
+        {
+            // Arrange
+            var package = new ServerPackage
+            {
+                Version = new SemanticVersion("0.1.0"),
+                Authors = Enumerable.Empty<string>(),
+                Owners = Enumerable.Empty<string>(),
+
+                Listed = false,
+                Created = new DateTimeOffset(2017, 11, 29, 21, 21, 32, TimeSpan.FromHours(-8)),
+            };
+
+            // Act
+            var actual = package.AsODataPackage(ClientCompatibility.Max);
+
+            // Assert
+            Assert.Equal(
+                new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc),
+                actual.Published);
+        }
+
+        [Fact]
+        public void AsODataPackage_UsesCreatedForListedPublished()
+        {
+            // Arrange
+            var package = new ServerPackage
+            {
+                Version = new SemanticVersion("0.1.0"),
+                Authors = Enumerable.Empty<string>(),
+                Owners = Enumerable.Empty<string>(),
+
+                Listed = true,
+                Created = new DateTimeOffset(2017, 11, 29, 21, 21, 32, TimeSpan.FromHours(-8)),
+            };
+
+            // Act
+            var actual = package.AsODataPackage(ClientCompatibility.Max);
+
+            // Assert
+            Assert.Equal(
+                new DateTime(2017, 11, 30, 5, 21, 32, DateTimeKind.Utc),
+                actual.Published);
+        }
+
         [Theory]
         [InlineData(true, true, false, false, 1, true, true)]
         [InlineData(false, false, true, true, 1, false, false)]