[Bug Fix] Packages with empty descriptions cause HTTP 500 on reflows (#9001)

* Fixed empty description -> null bug, added a uit test

* Fixed null description processing to only correct null/empty descriptions on reflow

Author: advay26

src/NuGetGallery.Core/Packaging/PackageMetadata.cs

@@ -273,14 +273,22 @@ public static PackageMetadata FromNuspecReader(NuspecReader nuspecReader, bool s
                 }
             }
 
-            return new PackageMetadata(
+            var packageMetadata = new PackageMetadata(
                 nuspecReader.GetMetadata().ToDictionary(kvp => kvp.Key, kvp => kvp.Value),
                 nuspecReader.GetDependencyGroups(useStrictVersionCheck: strict),
                 nuspecReader.GetFrameworkAssemblyGroups(),
                 nuspecReader.GetPackageTypes(),
                 nuspecReader.GetMinClientVersion(),
                 nuspecReader.GetRepositoryMetadata(),
                 nuspecReader.GetLicenseMetadata());
+
+            // Fix null or empty description values for reflowed packages
+            if (!strict)
+            {
+                packageMetadata.Description = packageMetadata.Description ?? string.Empty;
+            }
+
+            return packageMetadata;
         }
 
         private class StrictNuspecReader : NuspecReader

tests/NuGetGallery.Core.Facts/Packaging/PackageMetadataFacts.cs

@@ -205,6 +205,40 @@ public void CanReadBasicMetadataProperties()
             Assert.Equal("git", packageMetadata.RepositoryType);
         }
 
+        [Fact]
+        public void CanProcessEmptyNuspecDescriptionValueOnReflow()
+        {
+            // Arrange
+            var packageStream = CreateTestPackageStreamWithEmptyDescription();
+            var nupkg = new PackageArchiveReader(packageStream, leaveStreamOpen: false);
+            var nuspec = nupkg.GetNuspecReader();
+
+            // Act
+            var packageMetadata = PackageMetadata.FromNuspecReader(
+                nuspec,
+                strict: false);
+
+            // Assert
+            Assert.NotNull(packageMetadata.Description);
+        }
+
+        [Fact]
+        public void DoesNotFixEmptyNuspecDescriptionValueOnUpload()
+        {
+            // Arrange
+            var packageStream = CreateTestPackageStreamWithEmptyDescription();
+            var nupkg = new PackageArchiveReader(packageStream, leaveStreamOpen: false);
+            var nuspec = nupkg.GetNuspecReader();
+
+            // Act
+            var packageMetadata = PackageMetadata.FromNuspecReader(
+                nuspec,
+                strict: true);
+
+            // Assert
+            Assert.Null(packageMetadata.Description);
+        }
+
         [Theory]
         [InlineData(false)]
         [InlineData(true)]
@@ -360,6 +394,22 @@ private static Stream CreateTestPackageStream()
                     </package>");
         }
 
+        private static Stream CreateTestPackageStreamWithEmptyDescription()
+        {
+            return CreateTestPackageStream(@"<?xml version=""1.0""?>
+                    <package xmlns=""http://schemas.microsoft.com/packaging/2011/08/nuspec.xsd"">
+                      <metadata>
+                        <id>TestPackage</id>
+                        <version>0.0.0.1</version>
+                        <title>Package A</title>
+                        <authors>authora, authorb</authors>
+                        <owners>ownera, ownerb</owners>
+                        <requireLicenseAcceptance>false</requireLicenseAcceptance>
+                        <description></description>
+                      </metadata>
+                    </package>");
+        }
+
         private static Stream CreateTestPackageStreamWithMetadataElementName(string metadataName, string value = "some value")
         {
             return CreateTestPackageStream($@"<?xml version=""1.0""?>