Loading old model files is broken.

build/Dependencies.props

@@ -1,24 +1,44 @@
 <Project>
+
+  <!-- Core Product Dependencies -->
   <PropertyGroup>
-    <GoogleProtobufPackageVersion>3.5.1</GoogleProtobufPackageVersion>
     <NewtonsoftJsonPackageVersion>10.0.3</NewtonsoftJsonPackageVersion>
-    <ParquetDotNetPackageVersion>2.1.3</ParquetDotNetPackageVersion>
-    <SystemThreadingTasksDataflowPackageVersion>4.8.0</SystemThreadingTasksDataflowPackageVersion>
     <SystemCodeDomPackageVersion>4.4.0</SystemCodeDomPackageVersion>
+    <SystemCollectionsImmutableVersion>1.5.0</SystemCollectionsImmutableVersion>
+    <SystemMemoryVersion>4.5.1</SystemMemoryVersion>
     <SystemReflectionEmitLightweightPackageVersion>4.3.0</SystemReflectionEmitLightweightPackageVersion>
-    <PublishSymbolsPackageVersion>1.0.0-beta-62824-02</PublishSymbolsPackageVersion>
+    <SystemThreadingTasksDataflowPackageVersion>4.8.0</SystemThreadingTasksDataflowPackageVersion>
+  </PropertyGroup>
+
+  <!-- Other/Non-Core Product Dependencies -->
+  <PropertyGroup>
+    <GoogleProtobufPackageVersion>3.5.1</GoogleProtobufPackageVersion>
     <LightGBMPackageVersion>2.2.1.1</LightGBMPackageVersion>
+    <MicrosoftMLScoring>1.1.0</MicrosoftMLScoring>
     <MlNetMklDepsPackageVersion>0.0.0.7</MlNetMklDepsPackageVersion>
+    <ParquetDotNetPackageVersion>2.1.3</ParquetDotNetPackageVersion>
     <SystemDrawingCommonPackageVersion>4.5.0</SystemDrawingCommonPackageVersion>
-    <BenchmarkDotNetVersion>0.11.1</BenchmarkDotNetVersion>
+    <SystemIOFileSystemAccessControl>4.5.0</SystemIOFileSystemAccessControl>
+    <SystemSecurityPrincipalWindows>4.5.0</SystemSecurityPrincipalWindows>
     <TensorFlowVersion>1.10.0</TensorFlowVersion>
-    <SystemCollectionsImmutableVersion>1.5.0</SystemCollectionsImmutableVersion>
-    <SystemMemoryVersion>4.5.1</SystemMemoryVersion>
+  </PropertyGroup>
+
+  <!-- Code Analyzer Dependencies -->
+  <PropertyGroup>
     <MicrosoftCodeAnalysisCSharpVersion>2.9.0</MicrosoftCodeAnalysisCSharpVersion>
     <MicrosoftCSharpVersion>4.5.0</MicrosoftCSharpVersion>
     <SystemCompositionVersion>1.2.0</SystemCompositionVersion>
-    <MicrosoftMLScoring>1.1.0</MicrosoftMLScoring>
-    <SystemIOFileSystemAccessControl>4.5.0</SystemIOFileSystemAccessControl>
-    <SystemSecurityPrincipalWindows>4.5.0</SystemSecurityPrincipalWindows>
   </PropertyGroup>
+
+  <!-- Build/infrastructure Dependencies -->
+  <PropertyGroup>
+    <PublishSymbolsPackageVersion>1.0.0-beta-62824-02</PublishSymbolsPackageVersion>
+  </PropertyGroup>
+
+  <!-- Test-only Dependencies -->
+  <PropertyGroup>
+    <BenchmarkDotNetVersion>0.11.1</BenchmarkDotNetVersion>
+    <MicrosoftMLTestModelsPackageVersion>0.0.2-test</MicrosoftMLTestModelsPackageVersion>
+  </PropertyGroup>
+
 </Project>

src/Microsoft.ML.Data/Model/ModelHeader.cs

@@ -483,6 +483,18 @@ public static bool TryValidate(ref ModelHeader header, BinaryReader reader, long
                 {
                     // No strings.
                     strings = null;
+
+                    if (header.VerWritten < VerAssemblyNameSupported)
+                    {
+                        // Before VerAssemblyNameSupported, if there were no strings in the model,
+                        // validation ended here. Specifically the FpTail checks below were skipped.
+                        // There are earlier versions of models that don't have strings, and 'reader' is
+                        // not at FpTail at this point.
+                        // Preserve the previous behavior by returning early here.
+                        loaderAssemblyName = null;
+                        ex = null;
+                        return true;
+                    }
                 }
                 else
                 {

test/Microsoft.ML.Core.Tests/Microsoft.ML.Core.Tests.csproj

@@ -2,7 +2,7 @@
   <PropertyGroup>
     <DefineConstants>CORECLR</DefineConstants>
   </PropertyGroup>
-  
+
   <ItemGroup>
     <ProjectReference Include="..\..\src\Microsoft.ML.HalLearners\Microsoft.ML.HalLearners.csproj" />
     <ProjectReference Include="..\..\src\Microsoft.ML.Api\Microsoft.ML.Api.csproj" />
@@ -22,7 +22,11 @@
     <ProjectReference Include="..\..\src\Microsoft.ML.Legacy\Microsoft.ML.Legacy.csproj" />
     <ProjectReference Include="..\Microsoft.ML.TestFramework\Microsoft.ML.TestFramework.csproj" />
     <ProjectReference Include="..\Microsoft.ML.Tests\Microsoft.ML.Tests.csproj" />
-	<PackageReference Include="MlNetMklDeps" Version="$(MlNetMklDepsPackageVersion)" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="MlNetMklDeps" Version="$(MlNetMklDepsPackageVersion)" />
+    <PackageReference Include="Microsoft.ML.TestModels" Version="$(MicrosoftMLTestModelsPackageVersion)" />
   </ItemGroup>
 
   <ItemGroup>

test/Microsoft.ML.Core.Tests/UnitTests/TestModelLoad.cs

@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.ML.Runtime.Data;
+using Microsoft.ML.Runtime.Model;
+using Microsoft.ML.TestFramework;
+using System.IO;
+using Xunit;
+
+namespace Microsoft.ML.Runtime.RunTests
+{
+    public class TestModelLoad
+    {
+        /// <summary>
+        /// Tests loading a model file that was saved using an older version still loads correctly.
+        /// </summary>
+        [Fact]
+        public void LoadOriginalBinaryLoaderModel()
+        {
+            using (var env = new LocalEnvironment()
+                .AddStandardComponents())
+            using (var modelStream = File.OpenRead(Path.Combine("TestModels", "BinaryLoader-v3.11.0.0.zip")))
+            using (var rep = RepositoryReader.Open(modelStream, env))
+            {
+                IDataLoader result = ModelFileUtils.LoadLoader(env, rep, new MultiFileSource(null), true);
+
+                Assert.Equal(2, result.Schema.ColumnCount);
+                Assert.Equal("Image", result.Schema[0].Name);
+                Assert.Equal("Class", result.Schema[1].Name);
+            }
+        }
+    }
+}