Target net451 in ProjectModel

Fixes #876

src/Microsoft.DotNet.ProjectModel/CommonCompilerOptions.cs

@@ -58,7 +58,7 @@ namespace Microsoft.DotNet.ProjectModel
         }
 
         private static bool EnumerableEquals(IEnumerable<string> left, IEnumerable<string> right)
-            => Enumerable.SequenceEqual(left ?? Array.Empty<string>(), right ?? Array.Empty<string>());
+            => Enumerable.SequenceEqual(left ?? EmptyArray<string>.Value, right ?? EmptyArray<string>.Value);
 
         public override int GetHashCode()
         {
@@ -69,7 +69,7 @@ namespace Microsoft.DotNet.ProjectModel
         {
             if (@new != null)
             {
-                old = old ?? Array.Empty<string>();
+                old = old ?? EmptyArray<string>.Value;
                 return old.Concat(@new).Distinct().ToArray();
             }
             return old;

src/Microsoft.DotNet.ProjectModel/Compilation/LibraryExporter.cs

@@ -162,7 +162,7 @@ namespace Microsoft.DotNet.ProjectModel.Compilation
             var analyzers = GetAnalyzerReferences(package);
 
             return new LibraryExport(package, compileAssemblies,
-                sourceReferences, runtimeAssemblies, Array.Empty<LibraryAsset>(), nativeLibraries, analyzers);
+                sourceReferences, runtimeAssemblies, EmptyArray<LibraryAsset>.Value, nativeLibraries, analyzers);
         }
 
         private LibraryExport ExportProject(ProjectDescription project)
@@ -175,8 +175,8 @@ namespace Microsoft.DotNet.ProjectModel.Compilation
                                          sourceReferences: Enumerable.Empty<string>(),
                                          nativeLibraries: Enumerable.Empty<LibraryAsset>(),
                                          runtimeAssets: Enumerable.Empty<LibraryAsset>(),
-                                         runtimeAssemblies: Array.Empty<LibraryAsset>(),
+                                         runtimeAssemblies: EmptyArray<LibraryAsset>.Value,
-                                         analyzers: Array.Empty<AnalyzerReference>());
+                                         analyzers: EmptyArray<AnalyzerReference>.Value);
             }
 
             var compileAssemblies = new List<LibraryAsset>();
@@ -226,7 +226,7 @@ namespace Microsoft.DotNet.ProjectModel.Compilation
             // just the same as compileAssemblies and nativeLibraries are empty
             // Also no support for analyzer projects
             return new LibraryExport(project, compileAssemblies, sourceReferences,
-                compileAssemblies, runtimeAssets, Array.Empty<LibraryAsset>(), Array.Empty<AnalyzerReference>());
+                compileAssemblies, runtimeAssets, EmptyArray<LibraryAsset>.Value, EmptyArray<AnalyzerReference>.Value);
         }
 
         private static string ResolvePath(Project project, string configuration, string path)
@@ -250,13 +250,13 @@ namespace Microsoft.DotNet.ProjectModel.Compilation
             return new LibraryExport(
                 library,
                 string.IsNullOrEmpty(library.Path) ?
-                    Array.Empty<LibraryAsset>() :
+                    EmptyArray<LibraryAsset>.Value :
                     new[] { new LibraryAsset(library.Identity.Name, library.Path, library.Path) },
-                Array.Empty<string>(),
+                EmptyArray<string>.Value,
-                Array.Empty<LibraryAsset>(),
+                EmptyArray<LibraryAsset>.Value,
-                Array.Empty<LibraryAsset>(),
+                EmptyArray<LibraryAsset>.Value,
-                Array.Empty<LibraryAsset>(),
+                EmptyArray<LibraryAsset>.Value,
-                Array.Empty<AnalyzerReference>());
+                EmptyArray<AnalyzerReference>.Value);
         }
 
         private IEnumerable<string> GetSharedSources(PackageDescription package)

src/Microsoft.DotNet.ProjectModel/FileNameSuffixes.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Runtime.InteropServices;
+using Microsoft.Extensions.PlatformAbstractions;
 
 namespace Microsoft.DotNet.ProjectModel
 {
@@ -11,11 +11,17 @@ namespace Microsoft.DotNet.ProjectModel
         {
             get
             {
-                if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) { return Windows; }
+                switch (PlatformServices.Default.Runtime.OperatingSystemPlatform)
-                if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux)) { return Linux; }
+                {
-                if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX)) { return OSX; }
+                    case Platform.Windows:
-
+                        return Windows;
-                throw new InvalidOperationException("Unknown Platform");
+                    case Platform.Darwin:
+                        return OSX;
+                    case Platform.Linux:
+                        return Linux;
+                    default:
+                        throw new InvalidOperationException("Unknown Platform");
+                }
             }
         }
 

src/Microsoft.DotNet.ProjectModel/Internal/EmptyArray.cs

@@ -0,0 +1,14 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.DotNet.ProjectModel
+{
+    internal static class EmptyArray<T>
+    {
+#if NET451
+        public static readonly T[] Value = new T[0];
+#else
+        public static readonly T[] Value = System.Array.Empty<T>();
+#endif
+    }
+}

src/Microsoft.DotNet.ProjectModel/ProjectReader.cs

@@ -144,9 +144,9 @@ namespace Microsoft.DotNet.ProjectModel
             project.CompilerName = rawProject.ValueAsString("compilerName");
             project.TestRunner = rawProject.ValueAsString("testRunner");
 
-            project.Authors = rawProject.ValueAsStringArray("authors") ?? Array.Empty<string>();
+            project.Authors = rawProject.ValueAsStringArray("authors") ?? EmptyArray<string>.Value;
-            project.Owners = rawProject.ValueAsStringArray("owners") ?? Array.Empty<string>();
+            project.Owners = rawProject.ValueAsStringArray("owners") ?? EmptyArray<string>.Value;
-            project.Tags = rawProject.ValueAsStringArray("tags") ?? Array.Empty<string>();
+            project.Tags = rawProject.ValueAsStringArray("tags") ?? EmptyArray<string>.Value;
 
             project.Language = rawProject.ValueAsString("language");
             project.ReleaseNotes = rawProject.ValueAsString("releaseNotes");

src/Microsoft.DotNet.ProjectModel/Resolution/FrameworkReferenceResolver.cs

@@ -5,10 +5,10 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using System.Runtime.InteropServices;
 using System.Runtime.Versioning;
 using System.Xml.Linq;
 using Microsoft.DotNet.ProjectModel.Utilities;
+using Microsoft.Extensions.PlatformAbstractions;
 using NuGet.Frameworks;
 
 namespace Microsoft.DotNet.ProjectModel.Resolution
@@ -60,7 +60,7 @@ namespace Microsoft.DotNet.ProjectModel.Resolution
                 return referenceAssembliesPath;
             }
 
-            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            if (PlatformServices.Default.Runtime.OperatingSystemPlatform != Platform.Windows)
             {
                 // There is no reference assemblies path outside of windows
                 // The environment variable can be used to specify one

src/Microsoft.DotNet.ProjectModel/Utilities/PathUtility.cs

@@ -3,7 +3,7 @@
 
 using System;
 using System.IO;
-using System.Runtime.InteropServices;
+using Microsoft.Extensions.PlatformAbstractions;
 
 namespace Microsoft.DotNet.ProjectModel.Utilities
 {
@@ -84,7 +84,7 @@ namespace Microsoft.DotNet.ProjectModel.Utilities
             }
 
             StringComparison compare;
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            if (PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows)
             {
                 compare = StringComparison.OrdinalIgnoreCase;
                 // check if paths are on the same volume

src/Microsoft.DotNet.ProjectModel/Utilities/VersionUtility.cs

@@ -1,7 +1,10 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
+#if !NET451
 using System.Runtime.Loader;
+#endif
+using System.Reflection;
 using System.Text;
 using NuGet.Versioning;
 
@@ -16,7 +19,11 @@ namespace Microsoft.DotNet.ProjectModel.Utilities
 
         internal static NuGetVersion GetAssemblyVersion(string path)
         {
+#if NET451
+            return new NuGetVersion(AssemblyName.GetAssemblyName(path).Version);
+#else
             return new NuGetVersion(AssemblyLoadContext.GetAssemblyName(path).Version);
+#endif
         }
 
         public static string RenderVersion(VersionRange range)

src/Microsoft.DotNet.ProjectModel/project.json

@@ -5,15 +5,9 @@
     },
     "description": "Types to model a .NET Project",
     "dependencies": {
-        "NETStandard.Library": "1.0.0-rc2-23811",
+    "System.Reflection.Metadata": "1.2.0-rc2-23811",
-        "System.Reflection.Metadata": "1.2.0-rc2-23811",
-        "System.Runtime.Loader": "4.0.0-rc2-23811",
-        "System.Dynamic.Runtime": "4.0.11-rc2-23811",
-        "System.Security.Cryptography.Algorithms": "4.0.0-rc2-23811",
-        "Microsoft.CSharp": "4.0.1-rc2-23811",
-        "System.Xml.XDocument": "4.0.11-rc2-23811",
-        "NuGet.Packaging": "3.4.0-beta-583",
 
+        "NuGet.Packaging": "3.4.0-beta-583",
         "Microsoft.Extensions.FileSystemGlobbing": "1.0.0-rc2-15996",
         "Microsoft.Extensions.JsonParser.Sources": {
             "type": "build",
@@ -28,11 +22,23 @@
             "version": "1.0.0-*"
         }
     },
-
     "frameworks": {
+    "net451": {
+      "frameworkAssemblies": {
+        "System.IO": ""
+      }
+    },
         "dnxcore50": {
-            "imports": "portable-net45+win8"
+      "imports": "portable-net45+win8",
+      "dependencies": {
+        "NETStandard.Library": "1.0.0-rc2-23811",
+        "System.Dynamic.Runtime": "4.0.11-rc2-23811",
+        "System.Runtime.Loader": "4.0.0-rc2-23811",
+        "System.Security.Cryptography.Algorithms": "4.0.0-rc2-23811",
+        "Microsoft.CSharp": "4.0.1-rc2-23811",
+        "System.Xml.XDocument": "4.0.11-rc2-23811"
         }
+    }
     },
     "scripts": {
     }

src/Microsoft.Extensions.Testing.Abstractions/project.json

@@ -12,15 +12,18 @@
     "dependencies": {
         "Newtonsoft.Json": "7.0.1",
         "Microsoft.DotNet.ProjectModel": "1.0.0-*",
-        "Microsoft.Extensions.Logging.Abstractions": "1.0.0-rc2-16040",
+    "Microsoft.Extensions.Logging.Abstractions": "1.0.0-rc2-16040"
+  },
+  "frameworks": {
+    "net451": { },
+    "dnxcore50": {
+      "imports": "portable-net45+win8",
+      "dependencies": {
         "NETStandard.Library": "1.0.0-rc2-23811",
         "System.Resources.ResourceManager": "4.0.1-rc2-23811",
         "System.Runtime.Serialization.Primitives": "4.1.0-rc2-23811"
-    },
-    "frameworks": {
-        "dnxcore50": {
-            "imports": "portable-net45+win8"
         }
+    }
     },
     "scripts": {
     }