Support parsing null dependencies from the lock file

#1950

src/Microsoft.Framework.Runtime/DependencyManagement/LockFileReader.cs

@@ -35,7 +35,7 @@ public LockFile Read(string filePath)
             }
         }
 
-        private LockFile Read(Stream stream)
+        internal LockFile Read(Stream stream)
         {
             try
             {
@@ -254,6 +254,10 @@ private string ReadString(JsonValue json)
             {
                 return (json as JsonString).Value;
             }
+            else if(json is JsonNull)
+            {
+                return null;
+            }
             else
             {
                 throw FileFormatException.Create("The value type is not string.", json);

test/Microsoft.Framework.Runtime.Tests/LockFileReaderFacts.cs

@@ -0,0 +1,79 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.Framework.Runtime.DependencyManagement;
+using NuGet;
+using Xunit;
+
+namespace Microsoft.Framework.Runtime.Tests
+{
+    public class LockFileReaderFacts
+    {
+        [Fact]
+        public void NullDependencyVersionsAreParsed()
+        {
+            var lockFileData = @"{
+  ""locked"": false,
+  ""version"": -9996,
+  ""targets"": {
+                "".NETFramework,Version=v4.5"": {
+                    ""WindowsAzure.ServiceBus/2.6.7"": {
+                        ""dependencies"": {
+                            ""Microsoft.WindowsAzure.ConfigurationManager"": null
+                        },
+        ""frameworkAssemblies"": [
+          ""System.ServiceModel"",
+          ""System.Xml"",
+          ""System.Runtime.Serialization""
+        ],
+        ""compile"": {
+          ""lib/net40-full/Microsoft.ServiceBus.dll"": {}
+        },
+        ""runtime"": {
+          ""lib/net40-full/Microsoft.ServiceBus.dll"": {}
+        }
+      }
+}
+  },
+  ""libraries"": {
+    ""WindowsAzure.ServiceBus/2.6.7"": {
+      ""sha512"": ""AhQ4nya0Pu0tGev/Geqt5+yBTI+ov66ginMHCm+HqmXezTIOSfBu7HOI5RuvmiQqM99AeTuASD6gMz+zWueHNQ=="",
+      ""files"": [
+        ""WindowsAzure.ServiceBus.2.6.7.nupkg"",
+        ""WindowsAzure.ServiceBus.2.6.7.nupkg.sha512"",
+        ""WindowsAzure.ServiceBus.nuspec"",
+        ""content/app.config.install.xdt"",
+        ""content/web.config.install.xdt"",
+        ""lib/net40-full/Microsoft.ServiceBus.dll"",
+        ""lib/net40-full/Microsoft.ServiceBus.xml""
+      ]
+    }
+  },
+  ""projectFileDependencyGroups"": {
+    """": [
+      ""WindowsAzure.ServiceBus >= 2.6.7""
+    ],
+    "".NETFramework,Version=v4.5"": []
+  }
+}";
+
+            var reader = new LockFileReader();
+
+            var stream = new MemoryStream(Encoding.UTF8.GetBytes(lockFileData));
+            var lockFile = reader.Read(stream);
+
+            Assert.False(lockFile.Islocked);
+            Assert.Equal(1, lockFile.Targets.Count);
+            var library = lockFile.Targets[0].Libraries[0];
+            Assert.Equal("WindowsAzure.ServiceBus", library.Name);
+            Assert.Equal(SemanticVersion.Parse("2.6.7"), library.Version);
+            Assert.Equal(1, library.Dependencies.Count);
+            var dependency = library.Dependencies[0];
+            Assert.Equal(dependency.Id, "Microsoft.WindowsAzure.ConfigurationManager");
+            Assert.Null(dependency.VersionSpec);
+        }
+    }
+}