PR Feedback and nearly full test coverage for resolvers

fix

resolve rebase issues

src/Microsoft.DotNet.Cli.Utils/CollectionsExtensions.cs

@@ -1,18 +0,0 @@
-// 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.
-
-using System.Collections.Generic;
-using System.Linq;
-
-namespace Microsoft.DotNet.Cli.Utils
-{
-    public static class CollectionsExtensions
-    {
-        public static IEnumerable<T> OrEmptyIfNull<T>(this IEnumerable<T> enumerable)
-        {
-            return enumerable == null
-                ? Enumerable.Empty<T>()
-                : enumerable;
-        }
-    }
-}

src/Microsoft.DotNet.Cli.Utils/CommandResolution/AbstractPathBasedCommandResolver.cs

@@ -48,7 +48,7 @@ namespace Microsoft.DotNet.Cli.Utils
 
             return _commandSpecFactory.CreateCommandSpec(
                     commandResolverArguments.CommandName,
-                    commandResolverArguments.CommandArguments.EmptyIfNull(),
+                    commandResolverArguments.CommandArguments.OrEmptyIfNull(),
                     commandPath,
                     GetCommandResolutionStrategy(),
                     _environment);

src/Microsoft.DotNet.Cli.Utils/CommandResolution/CommandResolverArguments.cs

@@ -22,7 +22,5 @@ namespace Microsoft.DotNet.Cli.Utils
         public string Configuration { get; set; }
 
         public IEnumerable<string> InferredExtensions { get; set; }
-
-        public IEnvironmentProvider Environment { get; set; }
     }
 }

src/Microsoft.DotNet.Cli.Utils/CommandResolution/DefaultCommandResolverPolicy.cs

@@ -11,9 +11,9 @@ using NuGet.Packaging;
 
 namespace Microsoft.DotNet.Cli.Utils
 {
-    public class DefaultCommandResolver : CompositeCommandResolver
+    public class DefaultCommandResolverPolicy
     {
-        public static DefaultCommandResolver Create()
+        public static CompositeCommandResolver Create()
         {
             var environment = new EnvironmentProvider();
             var packagedCommandSpecFactory = new PackagedCommandSpecFactory();
@@ -28,18 +28,22 @@ namespace Microsoft.DotNet.Cli.Utils
                 platformCommandSpecFactory = new GenericPlatformCommandSpecFactory();
             }
 
-            return new DefaultCommandResolver(environment, packagedCommandSpecFactory, platformCommandSpecFactory);
+            return CreateDefaultCommandResolver(environment, packagedCommandSpecFactory, platformCommandSpecFactory);
         }
 
-        public DefaultCommandResolver(
+        public static CompositeCommandResolver CreateDefaultCommandResolver(
             IEnvironmentProvider environment,
             IPackagedCommandSpecFactory packagedCommandSpecFactory,
-            IPlatformCommandSpecFactory platformCommandSpecFactory) : base()
+            IPlatformCommandSpecFactory platformCommandSpecFactory)
         {
-            AddCommandResolver(new RootedCommandResolver());
-            AddCommandResolver(new ProjectToolsCommandResolver(packagedCommandSpecFactory));
-            AddCommandResolver(new AppBaseCommandResolver(environment, platformCommandSpecFactory));
-            AddCommandResolver(new PathCommandResolver(environment, platformCommandSpecFactory));
+            var compositeCommandResolver = new CompositeCommandResolver();
+
+            compositeCommandResolver.AddCommandResolver(new RootedCommandResolver());
+            compositeCommandResolver.AddCommandResolver(new ProjectToolsCommandResolver(packagedCommandSpecFactory));
+            compositeCommandResolver.AddCommandResolver(new AppBaseCommandResolver(environment, platformCommandSpecFactory));
+            compositeCommandResolver.AddCommandResolver(new PathCommandResolver(environment, platformCommandSpecFactory));
+            
+            return compositeCommandResolver;
         }
     }
 }

src/Microsoft.DotNet.Cli.Utils/CommandResolution/ProjectDependenciesCommandResolver.cs

@@ -52,7 +52,7 @@ namespace Microsoft.DotNet.Cli.Utils
                     commandResolverArguments.Framework,
                     commandResolverArguments.Configuration,
                     commandResolverArguments.CommandName,
-                    commandResolverArguments.CommandArguments,
+                    commandResolverArguments.CommandArguments.OrEmptyIfNull(),
                     commandResolverArguments.OutputPath);
         }
 

src/Microsoft.DotNet.Cli.Utils/CommandResolution/ProjectPathCommandResolver.cs

@@ -26,7 +26,7 @@ namespace Microsoft.DotNet.Cli.Utils
             return _environment.GetCommandPathFromRootPath(
                 commandResolverArguments.ProjectDirectory, 
                 commandResolverArguments.CommandName,
-                commandResolverArguments.InferredExtensions.EmptyIfNull());
+                commandResolverArguments.InferredExtensions.OrEmptyIfNull());
         }
 
         internal override CommandResolutionStrategy GetCommandResolutionStrategy()

src/Microsoft.DotNet.Cli.Utils/CommandResolution/ProjectToolsCommandResolver.cs

@@ -32,9 +32,15 @@ namespace Microsoft.DotNet.Cli.Utils
 
         public CommandSpec Resolve(CommandResolverArguments commandResolverArguments)
         {
+            if (commandResolverArguments.CommandName == null
+                || commandResolverArguments.ProjectDirectory == null)
+            {
+                return null;
+            }
+            
             return ResolveFromProjectTools(
                 commandResolverArguments.CommandName, 
-                commandResolverArguments.CommandArguments,
+                commandResolverArguments.CommandArguments.OrEmptyIfNull(),
                 commandResolverArguments.ProjectDirectory);
         }
 
@@ -50,7 +56,7 @@ namespace Microsoft.DotNet.Cli.Utils
                 return null;
             }
 
-            var toolsLibraries = projectContext.ProjectFile.Tools.EmptyIfNull();
+            var toolsLibraries = projectContext.ProjectFile.Tools.OrEmptyIfNull();
 
             return ResolveCommandSpecFromAllToolLibraries(
                 toolsLibraries,

src/Microsoft.DotNet.Cli.Utils/CommandResolution/RootedCommandResolver.cs

@@ -23,7 +23,7 @@ namespace Microsoft.DotNet.Cli.Utils
             if (Path.IsPathRooted(commandResolverArguments.CommandName))
             {
                 var escapedArgs = ArgumentEscaper.EscapeAndConcatenateArgArrayForProcessStart(
-                    commandResolverArguments.CommandArguments.EmptyIfNull());
+                    commandResolverArguments.CommandArguments.OrEmptyIfNull());
 
                 return new CommandSpec(commandResolverArguments.CommandName, escapedArgs, CommandResolutionStrategy.RootedPath);
             }

src/Microsoft.DotNet.Cli.Utils/CommandResolution/ScriptCommandResolverPolicy.cs

@@ -11,9 +11,9 @@ using NuGet.Packaging;
 
 namespace Microsoft.DotNet.Cli.Utils
 {
-    public class ScriptCommandResolver : CompositeCommandResolver
+    public class ScriptCommandResolverPolicy
     {
-        public static ScriptCommandResolver Create()
+        public static CompositeCommandResolver Create()
         {
             var environment = new EnvironmentProvider();
 
@@ -27,17 +27,21 @@ namespace Microsoft.DotNet.Cli.Utils
                 platformCommandSpecFactory = new GenericPlatformCommandSpecFactory();
             }
 
-            return new ScriptCommandResolver(environment, platformCommandSpecFactory);
+            return CreateScriptCommandResolver(environment, platformCommandSpecFactory);
         }
 
-        public ScriptCommandResolver(
+        public static CompositeCommandResolver CreateScriptCommandResolver(
             IEnvironmentProvider environment,
             IPlatformCommandSpecFactory platformCommandSpecFactory)
         {
-            AddCommandResolver(new RootedCommandResolver());
-            AddCommandResolver(new ProjectPathCommandResolver(environment, platformCommandSpecFactory));
-            AddCommandResolver(new AppBaseCommandResolver(environment, platformCommandSpecFactory));
-            AddCommandResolver(new PathCommandResolver(environment, platformCommandSpecFactory));
+            var compositeCommandResolver = new CompositeCommandResolver();
+
+            compositeCommandResolver.AddCommandResolver(new RootedCommandResolver());
+            compositeCommandResolver.AddCommandResolver(new ProjectPathCommandResolver(environment, platformCommandSpecFactory));
+            compositeCommandResolver.AddCommandResolver(new AppBaseCommandResolver(environment, platformCommandSpecFactory));
+            compositeCommandResolver.AddCommandResolver(new PathCommandResolver(environment, platformCommandSpecFactory));
+        
+            return compositeCommandResolver;
         }
     }
 }

src/Microsoft.DotNet.Cli.Utils/CommandResolver.cs

@@ -13,9 +13,6 @@ namespace Microsoft.DotNet.Cli.Utils
 {
     internal static class CommandResolver
     {
-        private static DefaultCommandResolver _defaultCommandResolver;
-        private static ScriptCommandResolver _scriptCommandResolver;
-
         public static CommandSpec TryResolveCommandSpec(
             string commandName, 
             IEnumerable<string> args, 
@@ -33,12 +30,9 @@ namespace Microsoft.DotNet.Cli.Utils
                 OutputPath = outputPath
             };
             
-            if (_defaultCommandResolver == null)
-            {
-                _defaultCommandResolver = DefaultCommandResolver.Create();
-            }
+            var defaultCommandResolver = DefaultCommandResolverPolicy.Create();
             
-            return _defaultCommandResolver.Resolve(commandResolverArgs);
+            return defaultCommandResolver.Resolve(commandResolverArgs);
         }
         
         public static CommandSpec TryResolveScriptCommandSpec(
@@ -55,12 +49,9 @@ namespace Microsoft.DotNet.Cli.Utils
                 InferredExtensions = inferredExtensionList
             };
 
-            if (_scriptCommandResolver == null)
-            {
-                _scriptCommandResolver = ScriptCommandResolver.Create();
-            }
+            var scriptCommandResolver = ScriptCommandResolverPolicy.Create();
             
-            return _scriptCommandResolver.Resolve(commandResolverArgs);
+            return scriptCommandResolver.Resolve(commandResolverArgs);
         }
     }
 }

src/Microsoft.DotNet.Cli.Utils/CoreHost.cs

@@ -1,3 +1,4 @@
+using System;
 using System.IO;
 using Microsoft.Extensions.PlatformAbstractions;
 

src/Microsoft.DotNet.Cli.Utils/EnvironmentProvider.cs

@@ -50,12 +50,12 @@ namespace Microsoft.DotNet.Cli.Utils
             }
         }
 
-        public EnvironmentProvider(IEnumerable<string> extensionsOverride = null)
+        public EnvironmentProvider(
+            IEnumerable<string> extensionsOverride = null,
+            IEnumerable<string> searchPathsOverride = null)
         {
-            if (extensionsOverride != null)
-            {
-                _executableExtensions = extensionsOverride;
-            }
+            _executableExtensions = extensionsOverride;
+            _searchPaths = searchPathsOverride;
         }
 
         public string GetCommandPath(string commandName, params string[] extensions)
@@ -89,7 +89,7 @@ namespace Microsoft.DotNet.Cli.Utils
 
         public string GetCommandPathFromRootPath(string rootPath, string commandName, IEnumerable<string> extensions)
         {
-            var extensionsArr = extensions.EmptyIfNull().ToArray();
+            var extensionsArr = extensions.OrEmptyIfNull().ToArray();
 
             return GetCommandPathFromRootPath(rootPath, commandName, extensionsArr);
         }

src/Microsoft.DotNet.Cli.Utils/Extensions/CollectionsExtensions.cs

@@ -6,7 +6,7 @@ namespace Microsoft.DotNet.Cli.Utils
 {
     public static class CollectionsExtensions
     {
-        public static IEnumerable<T> EmptyIfNull<T>(this IEnumerable<T> enumerable)
+        public static IEnumerable<T> OrEmptyIfNull<T>(this IEnumerable<T> enumerable)
         {
             return enumerable == null 
                 ? Enumerable.Empty<T>()

test/Microsoft.DotNet.Cli.Utils.Tests/CommandResolverTestUtils.cs

@@ -8,13 +8,15 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
 {
     public static class CommandResolverTestUtils
     {
-        public static void CreateNonRunnableTestCommand(string directory, string filename, string extension=".dll")
+        public static string CreateNonRunnableTestCommand(string directory, string filename, string extension=".dll")
         {
             Directory.CreateDirectory(directory);
             
             var filePath = Path.Combine(directory, filename + extension);
 
             File.WriteAllText(filePath, "test command that does nothing.");
+
+            return filePath;
         }
 
         public static IEnvironmentProvider SetupEnvironmentProviderWhichFindsExtensions(params string[] extensions)

test/Microsoft.DotNet.Cli.Utils.Tests/GivenADefaultCommandResolver.cs

@@ -24,7 +24,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         [Fact]
         public void It_contains_resolvers_in_the_right_order()
         {
-            var defaultCommandResolver = DefaultCommandResolver.Create();
+            var defaultCommandResolver = DefaultCommandResolverPolicy.Create();
 
             var resolvers = defaultCommandResolver.OrderedCommandResolvers;
 

test/Microsoft.DotNet.Cli.Utils.Tests/GivenAPathCommandResolver.cs

@@ -0,0 +1,218 @@
+// 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.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Linq;
+using Xunit;
+using Moq;
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.DotNet.ProjectModel;
+using Microsoft.DotNet.Tools.Test.Utilities;
+using Microsoft.Extensions.PlatformAbstractions;
+using System.Threading;
+using FluentAssertions;
+using NuGet.Frameworks;
+
+namespace Microsoft.DotNet.Cli.Utils.Tests
+{
+    public class GivenAPathCommandResolver
+    {
+        private static readonly string s_testDirectory = Path.Combine(AppContext.BaseDirectory, "pathTestDirectory");
+
+        [Fact]
+        public void It_returns_null_when_CommandName_is_null()
+        {
+            var pathCommandResolver = SetupPlatformPathCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = null,
+                CommandArguments = null
+            };
+
+            var result = pathCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_null_when_CommandName_does_not_exist_in_PATH()
+        {
+            var emptyPathEnvironmentMock = new Mock<IEnvironmentProvider>();
+            emptyPathEnvironmentMock.Setup(e => e
+                .GetCommandPath(It.IsAny<string>(), It.IsAny<string[]>()))
+                .Returns((string)null);
+
+            var pathCommandResolver = SetupPlatformPathCommandResolver(emptyPathEnvironmentMock.Object);
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "nonexistent-command",
+                CommandArguments = null
+            };
+
+            var result = pathCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_a_CommandSpec_with_CommandName_as_FileName_when_CommandName_exists_in_PATH()
+        {
+            var testCommandPath = CommandResolverTestUtils.CreateNonRunnableTestCommand(
+                s_testDirectory, 
+                "pathtestcommand1", 
+                ".exe");
+
+            var staticPathEnvironmentMock = new Mock<IEnvironmentProvider>();
+            staticPathEnvironmentMock.Setup(e => e
+                .GetCommandPath(It.IsAny<string>(), It.IsAny<string[]>()))
+                .Returns(testCommandPath); 
+
+            var pathCommandResolver = SetupPlatformPathCommandResolver(staticPathEnvironmentMock.Object, forceGeneric: true);
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = Path.GetFileNameWithoutExtension(testCommandPath),
+                CommandArguments = null
+            };
+
+            var result = pathCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+
+            var commandFile = Path.GetFileNameWithoutExtension(result.Path);
+
+            commandFile.Should().Be(Path.GetFileNameWithoutExtension(testCommandPath));
+        }
+
+        [Fact]
+        public void It_escapes_CommandArguments_when_returning_a_CommandSpec()
+        {
+            var testCommandPath = CommandResolverTestUtils.CreateNonRunnableTestCommand(
+                s_testDirectory, 
+                "pathtestcommand1", 
+                ".exe");
+
+            var staticPathEnvironmentMock = new Mock<IEnvironmentProvider>();
+            staticPathEnvironmentMock.Setup(e => e
+                .GetCommandPath(It.IsAny<string>(), It.IsAny<string[]>()))
+                .Returns(testCommandPath); 
+
+            var pathCommandResolver = SetupPlatformPathCommandResolver(staticPathEnvironmentMock.Object, forceGeneric: true);
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = Path.GetFileNameWithoutExtension(testCommandPath),
+                CommandArguments = new [] {"arg with space"}
+            };
+
+            var result = pathCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+            result.Args.Should().Be("\"arg with space\"");
+        }
+
+        [Fact]
+        public void It_returns_a_CommandSpec_with_Args_as_stringEmpty_when_returning_a_CommandSpec_and_CommandArguments_are_null()
+        {
+            var testCommandPath = CommandResolverTestUtils.CreateNonRunnableTestCommand(
+                s_testDirectory, 
+                "pathtestcommand1", 
+                ".exe");
+
+            var staticPathEnvironmentMock = new Mock<IEnvironmentProvider>();
+            staticPathEnvironmentMock.Setup(e => e
+                .GetCommandPath(It.IsAny<string>(), It.IsAny<string[]>()))
+                .Returns(testCommandPath); 
+
+            var pathCommandResolver = SetupPlatformPathCommandResolver(staticPathEnvironmentMock.Object, forceGeneric: true);
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = Path.GetFileNameWithoutExtension(testCommandPath),
+                CommandArguments = null
+            };
+
+            var result = pathCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+            result.Args.Should().Be(string.Empty);
+        }
+
+        [Fact]
+        public void It_prefers_EXE_over_CMD_when_two_command_candidates_exist_and_using_WindowsExePreferredCommandSpecFactory()
+        {
+            var environment = new EnvironmentProvider(new [] {".exe", ".cmd"}, new[] { s_testDirectory });
+            var platformCommandSpecFactory = new WindowsExePreferredCommandSpecFactory();
+
+            var pathCommandResolver = new PathCommandResolver(environment, platformCommandSpecFactory);
+
+            CommandResolverTestUtils.CreateNonRunnableTestCommand(s_testDirectory, "extensionPreferenceCommand", ".exe");
+            CommandResolverTestUtils.CreateNonRunnableTestCommand(s_testDirectory, "extensionPreferenceCommand", ".cmd");
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "extensionPreferenceCommand",
+                CommandArguments = null
+            };
+
+            var result = pathCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+
+            var commandFile = Path.GetFileName(result.Path);
+            commandFile.Should().Be("extensionPreferenceCommand.exe");
+        }
+
+        [Fact]
+        public void It_wraps_command_with_CMD_EXE_when_command_has_CMD_Extension_and_using_WindowsExePreferredCommandSpecFactory()
+        {
+            var environment = new EnvironmentProvider(new [] {".cmd"}, new[] { s_testDirectory });
+            var platformCommandSpecFactory = new WindowsExePreferredCommandSpecFactory();
+
+            var pathCommandResolver = new PathCommandResolver(environment, platformCommandSpecFactory);
+
+            var testCommandPath = 
+                CommandResolverTestUtils.CreateNonRunnableTestCommand(s_testDirectory, "cmdWrapCommand", ".cmd");
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "cmdWrapCommand",
+                CommandArguments = null
+            };
+
+            var result = pathCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+
+            var commandFile = Path.GetFileName(result.Path);
+            commandFile.Should().Be("cmd.exe");
+
+            result.Args.Should().Contain(testCommandPath);
+        }
+
+        private PathCommandResolver SetupPlatformPathCommandResolver(
+            IEnvironmentProvider environment = null, 
+            bool forceGeneric = false)
+        {
+            environment = environment ?? new EnvironmentProvider();
+
+            IPlatformCommandSpecFactory platformCommandSpecFactory = new GenericPlatformCommandSpecFactory();
+
+            if (PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows
+                && !forceGeneric)
+            {
+                platformCommandSpecFactory = new WindowsExePreferredCommandSpecFactory();
+            }
+
+            var pathCommandResolver = new PathCommandResolver(environment, platformCommandSpecFactory);
+
+            return pathCommandResolver;
+        }
+    }
+}

test/Microsoft.DotNet.Cli.Utils.Tests/GivenAProjectDependencyCommandResolver.cs

@@ -0,0 +1,221 @@
+// 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.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Linq;
+using Xunit;
+using Moq;
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.DotNet.ProjectModel;
+using Microsoft.DotNet.Tools.Test.Utilities;
+using Microsoft.Extensions.PlatformAbstractions;
+using System.Threading;
+using FluentAssertions;
+using NuGet.Frameworks;
+
+namespace Microsoft.DotNet.Cli.Utils.Tests
+{
+    public class GivenAProjectDependenciesCommandResolver
+    {
+
+        private static readonly string s_liveProjectDirectory = 
+            Path.Combine(AppContext.BaseDirectory, "TestAssets/TestProjects/AppWithDirectDependency");
+
+        [Fact]
+        public void It_returns_null_when_CommandName_is_null()
+        {
+            var projectDependenciesCommandResolver = SetupProjectDependenciesCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = null,
+                CommandArguments = new string[] {""},
+                ProjectDirectory = "/some/directory",
+                Configuration = "Debug",
+                Framework = FrameworkConstants.CommonFrameworks.NetStandardApp15
+            };
+
+            var result = projectDependenciesCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_null_when_ProjectDirectory_is_null()
+        {
+            var projectDependenciesCommandResolver = SetupProjectDependenciesCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "command",
+                CommandArguments = new string[] {""},
+                ProjectDirectory = null,
+                Configuration = "Debug",
+                Framework = FrameworkConstants.CommonFrameworks.NetStandardApp15
+            };
+
+            var result = projectDependenciesCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_null_when_Framework_is_null()
+        {
+            var projectDependenciesCommandResolver = SetupProjectDependenciesCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "command",
+                CommandArguments = new string[] {""},
+                ProjectDirectory = s_liveProjectDirectory,
+                Configuration = "Debug",
+                Framework = null
+            };
+
+            var result = projectDependenciesCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_null_when_Configuration_is_null()
+        {
+            var projectDependenciesCommandResolver = SetupProjectDependenciesCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "command",
+                CommandArguments = new string[] {""},
+                ProjectDirectory = s_liveProjectDirectory,
+                Configuration = null,
+                Framework = FrameworkConstants.CommonFrameworks.NetStandardApp15
+            };
+
+            var result = projectDependenciesCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_null_when_CommandName_does_not_exist_in_ProjectDependencies()
+        {
+            var projectDependenciesCommandResolver = SetupProjectDependenciesCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "nonexistent-command",
+                CommandArguments = null,
+                ProjectDirectory = s_liveProjectDirectory,
+                Configuration = "Debug",
+                Framework = FrameworkConstants.CommonFrameworks.NetStandardApp15
+            };
+
+            var result = projectDependenciesCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_a_CommandSpec_with_CoreHost_as_FileName_and_CommandName_in_Args_when_CommandName_exists_in_ProjectDependencies()
+        {
+            var projectDependenciesCommandResolver = SetupProjectDependenciesCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "dotnet-hello",
+                CommandArguments = null,
+                ProjectDirectory = s_liveProjectDirectory,
+                Configuration = "Debug",
+                Framework = FrameworkConstants.CommonFrameworks.NetStandardApp15
+            };
+
+            var result = projectDependenciesCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+
+            var commandFile = Path.GetFileNameWithoutExtension(result.Path);
+
+            commandFile.Should().Be("corehost");
+
+            result.Args.Should().Contain(commandResolverArguments.CommandName);
+        }
+
+        [Fact]
+        public void It_escapes_CommandArguments_when_returning_a_CommandSpec()
+        {
+            var projectDependenciesCommandResolver = SetupProjectDependenciesCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "dotnet-hello",
+                CommandArguments = new [] { "arg with space"},
+                ProjectDirectory = s_liveProjectDirectory,
+                Configuration = "Debug",
+                Framework = FrameworkConstants.CommonFrameworks.NetStandardApp15
+            };
+
+            var result = projectDependenciesCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+            result.Args.Should().Contain("\"arg with space\"");
+        }
+
+        [Fact]
+        public void It_passes_depsfile_arg_to_corehost_when_returning_a_commandspec()
+        {
+            var projectDependenciesCommandResolver = SetupProjectDependenciesCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "dotnet-hello",
+                CommandArguments = null,
+                ProjectDirectory = s_liveProjectDirectory,
+                Configuration = "Debug",
+                Framework = FrameworkConstants.CommonFrameworks.NetStandardApp15
+            };
+
+            var result = projectDependenciesCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+            result.Args.Should().Contain("--depsfile");
+        }
+
+        [Fact]
+        public void It_returns_a_CommandSpec_with_CommandName_in_Args_when_returning_a_CommandSpec_and_CommandArguments_are_null()
+        {
+            var projectDependenciesCommandResolver = SetupProjectDependenciesCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "dotnet-hello",
+                CommandArguments = null,
+                ProjectDirectory = s_liveProjectDirectory,
+                Configuration = "Debug",
+                Framework = FrameworkConstants.CommonFrameworks.NetStandardApp15
+            };
+
+            var result = projectDependenciesCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+            
+            result.Args.Should().Contain("dotnet-hello");
+        }
+
+        private ProjectDependenciesCommandResolver SetupProjectDependenciesCommandResolver(
+            IEnvironmentProvider environment = null,
+            IPackagedCommandSpecFactory packagedCommandSpecFactory = null)
+        {
+            environment = environment ?? new EnvironmentProvider();
+            packagedCommandSpecFactory = packagedCommandSpecFactory ?? new PackagedCommandSpecFactory();
+
+            var projectDependenciesCommandResolver = new ProjectDependenciesCommandResolver(environment, packagedCommandSpecFactory);
+
+            return projectDependenciesCommandResolver;
+        }
+    }
+}

test/Microsoft.DotNet.Cli.Utils.Tests/GivenAProjectPathCommandResolver.cs

@@ -26,7 +26,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         [Fact]
         public void It_returns_null_when_CommandName_is_null()
         {
-            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver();
+            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(forceGeneric: true);
 
             var commandResolverArguments = new CommandResolverArguments()
             {
@@ -43,7 +43,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         [Fact]
         public void It_returns_null_when_ProjectDirectory_is_null()
         {
-            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver();
+            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(forceGeneric: true);
 
             var commandResolverArguments = new CommandResolverArguments()
             {
@@ -60,7 +60,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         [Fact]
         public void It_returns_null_when_CommandName_does_not_exist_in_ProjectDirectory()
         {
-            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver();
+            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(forceGeneric: true);
 
             var commandResolverArguments = new CommandResolverArguments()
             {
@@ -78,7 +78,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         public void It_returns_null_when_CommandName_exists_in_a_subdirectory_of_ProjectDirectory()
         {
             var environment = CommandResolverTestUtils.SetupEnvironmentProviderWhichFindsExtensions(".exe");
-            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(environment);
+            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(environment, forceGeneric: true);
 
             var testDir = Path.Combine(s_testProjectDirectory, "projectpathtestsubdir");
             CommandResolverTestUtils.CreateNonRunnableTestCommand(testDir, "projectpathtestsubdircommand", ".exe");
@@ -99,7 +99,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         public void It_returns_a_CommandSpec_with_CommandName_as_FileName_when_CommandName_exists_in_ProjectDirectory()
         {
             var environment = CommandResolverTestUtils.SetupEnvironmentProviderWhichFindsExtensions(".exe");
-            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(environment);
+            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(environment, forceGeneric: true);
 
             CommandResolverTestUtils.CreateNonRunnableTestCommand(s_testProjectDirectory, "projectpathtestcommand1", ".exe");
 
@@ -123,7 +123,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         public void It_escapes_CommandArguments_when_returning_a_CommandSpec()
         {
             var environment = CommandResolverTestUtils.SetupEnvironmentProviderWhichFindsExtensions(".exe");
-            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(environment);
+            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(environment, forceGeneric: true);
 
             CommandResolverTestUtils.CreateNonRunnableTestCommand(s_testProjectDirectory, "projectpathtestcommand1", ".exe");
 
@@ -144,7 +144,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         public void It_resolves_commands_with_extensions_defined_in_InferredExtensions()
         {
             var extensions = new string[] {".sh", ".cmd", ".foo", ".exe"};
-            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver();
+            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(forceGeneric: true);
 
             foreach (var extension in extensions)
             {
@@ -173,7 +173,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         public void It_returns_a_CommandSpec_with_Args_as_stringEmpty_when_returning_a_CommandSpec_and_CommandArguments_are_null()
         {
             var environment = CommandResolverTestUtils.SetupEnvironmentProviderWhichFindsExtensions(".exe");
-            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(environment);
+            var projectPathCommandResolver = SetupPlatformProjectPathCommandResolver(environment, forceGeneric: true);
 
             CommandResolverTestUtils.CreateNonRunnableTestCommand(s_testProjectDirectory, "projectpathtestcommand1", ".exe");
 
@@ -216,20 +216,45 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
             commandFile.Should().Be("projectpathtestcommand1.exe");
         }
 
-        private ProjectPathCommandResolver SetupPlatformProjectPathCommandResolver(IEnvironmentProvider environment = null)
+        public void It_wraps_command_with_CMD_EXE_when_command_has_CMD_Extension_and_using_WindowsExePreferredCommandSpecFactory()
+        {
+            var environment = new EnvironmentProvider(new [] {".cmd"});
+            var platformCommandSpecFactory = new WindowsExePreferredCommandSpecFactory();
+
+            var pathCommandResolver = new PathCommandResolver(environment, platformCommandSpecFactory);
+
+            var testCommandPath = 
+                CommandResolverTestUtils.CreateNonRunnableTestCommand(s_testProjectDirectory, "cmdWrapCommand", ".cmd");
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "cmdWrapCommand",
+                CommandArguments = null
+            };
+
+            var result = pathCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+
+            var commandFile = Path.GetFileName(result.Path);
+            commandFile.Should().Be("cmd.exe");
+
+            result.Args.Should().Contain(testCommandPath);
+        }
+
+        private ProjectPathCommandResolver SetupPlatformProjectPathCommandResolver(
+            IEnvironmentProvider environment = null,
+            bool forceGeneric = false)
         {
             environment = environment ?? new EnvironmentProvider();
 
-            var platformCommandSpecFactory = default(IPlatformCommandSpecFactory);
+            IPlatformCommandSpecFactory platformCommandSpecFactory = new GenericPlatformCommandSpecFactory();
 
-            if (PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows)
+            if (PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows
+                && !forceGeneric)
             {
                 platformCommandSpecFactory = new WindowsExePreferredCommandSpecFactory();
             }
-            else
-            {
-                platformCommandSpecFactory = new GenericPlatformCommandSpecFactory();
-            }
 
             var projectPathCommandResolver = new ProjectPathCommandResolver(environment, platformCommandSpecFactory);
 

test/Microsoft.DotNet.Cli.Utils.Tests/GivenAProjectToolsCommandResolver.cs

@@ -0,0 +1,152 @@
+// 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.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Linq;
+using Xunit;
+using Moq;
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.DotNet.ProjectModel;
+using Microsoft.DotNet.Tools.Test.Utilities;
+using Microsoft.Extensions.PlatformAbstractions;
+using System.Threading;
+using FluentAssertions;
+using NuGet.Frameworks;
+
+namespace Microsoft.DotNet.Cli.Utils.Tests
+{
+    public class GivenAProjectToolsCommandResolver
+    {
+
+        private static readonly string s_liveProjectDirectory = 
+            Path.Combine(AppContext.BaseDirectory, "TestAssets/TestProjects/AppWithToolDependency");
+
+        [Fact]
+        public void It_returns_null_when_CommandName_is_null()
+        {
+            var projectToolsCommandResolver = SetupProjectToolsCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = null,
+                CommandArguments = new string[] {""},
+                ProjectDirectory = "/some/directory"
+            };
+
+            var result = projectToolsCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_null_when_ProjectDirectory_is_null()
+        {
+            var projectToolsCommandResolver = SetupProjectToolsCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "command",
+                CommandArguments = new string[] {""},
+                ProjectDirectory = null
+            };
+
+            var result = projectToolsCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_null_when_CommandName_does_not_exist_in_ProjectTools()
+        {
+            var projectToolsCommandResolver = SetupProjectToolsCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "nonexistent-command",
+                CommandArguments = null,
+                ProjectDirectory = s_liveProjectDirectory
+            };
+
+            var result = projectToolsCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().BeNull();
+        }
+
+        [Fact]
+        public void It_returns_a_CommandSpec_with_CoreHost_as_FileName_and_CommandName_in_Args_when_CommandName_exists_in_ProjectTools()
+        {
+            var projectToolsCommandResolver = SetupProjectToolsCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "dotnet-hello",
+                CommandArguments = null,
+                ProjectDirectory = s_liveProjectDirectory
+            };
+
+            var result = projectToolsCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+
+            var commandFile = Path.GetFileNameWithoutExtension(result.Path);
+
+            commandFile.Should().Be("corehost");
+
+            result.Args.Should().Contain(commandResolverArguments.CommandName);
+        }
+
+        [Fact]
+        public void It_escapes_CommandArguments_when_returning_a_CommandSpec()
+        {
+            var projectToolsCommandResolver = SetupProjectToolsCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "dotnet-hello",
+                CommandArguments = new [] { "arg with space"},
+                ProjectDirectory = s_liveProjectDirectory
+            };
+
+            var result = projectToolsCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+            result.Args.Should().Contain("\"arg with space\"");
+        }
+
+        [Fact]
+        public void It_returns_a_CommandSpec_with_Args_as_CommandPath_when_returning_a_CommandSpec_and_CommandArguments_are_null()
+        {
+            var projectToolsCommandResolver = SetupProjectToolsCommandResolver();
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "dotnet-hello",
+                CommandArguments = null,
+                ProjectDirectory = s_liveProjectDirectory
+            };
+
+            var result = projectToolsCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+            
+            var commandPath = result.Args.Trim('"');
+            commandPath.Should().Contain("dotnet-hello");
+
+            File.Exists(commandPath).Should().BeTrue();
+        }
+
+        private ProjectToolsCommandResolver SetupProjectToolsCommandResolver(
+            IPackagedCommandSpecFactory packagedCommandSpecFactory = null)
+        {
+            packagedCommandSpecFactory = packagedCommandSpecFactory ?? new PackagedCommandSpecFactory();
+
+            var projectToolsCommandResolver = new ProjectToolsCommandResolver(packagedCommandSpecFactory);
+
+            return projectToolsCommandResolver;
+        }
+    }
+}

test/Microsoft.DotNet.Cli.Utils.Tests/GivenAScriptCommandResolver.cs

@@ -24,7 +24,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         [Fact]
         public void It_contains_resolvers_in_the_right_order()
         {
-            var scriptCommandResolver = ScriptCommandResolver.Create();
+            var scriptCommandResolver = ScriptCommandResolverPolicy.Create();
 
             var resolvers = scriptCommandResolver.OrderedCommandResolvers;
 

test/Microsoft.DotNet.Cli.Utils.Tests/GivenAnAppBaseCommandResolver.cs

@@ -24,7 +24,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         [Fact]
         public void It_returns_null_when_CommandName_is_null()
         {
-            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver();
+            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(forceGeneric: true);
 
             var commandResolverArguments = new CommandResolverArguments()
             {
@@ -40,7 +40,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         [Fact]
         public void It_returns_null_when_CommandName_does_not_exist_applocal()
         {
-            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver();
+            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(forceGeneric: true);
 
             var commandResolverArguments = new CommandResolverArguments()
             {
@@ -57,7 +57,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         public void It_returns_a_CommandSpec_with_CommandName_as_FileName_when_CommandName_exists_applocal()
         {
             var environment = CommandResolverTestUtils.SetupEnvironmentProviderWhichFindsExtensions(".exe");
-            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(environment);
+            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(environment, forceGeneric: true);
 
             CommandResolverTestUtils.CreateNonRunnableTestCommand(AppContext.BaseDirectory, "appbasetestcommand1", ".exe");
 
@@ -80,7 +80,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         public void It_returns_null_when_CommandName_exists_applocal_in_a_subdirectory()
         {
             var environment = CommandResolverTestUtils.SetupEnvironmentProviderWhichFindsExtensions(".exe");
-            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(environment);
+            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(environment, forceGeneric: true);
 
             var testDir = Path.Combine(AppContext.BaseDirectory, "appbasetestsubdir");
             CommandResolverTestUtils.CreateNonRunnableTestCommand(testDir, "appbasetestsubdircommand", ".exe");
@@ -100,7 +100,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         public void It_escapes_CommandArguments_when_returning_a_CommandSpec()
         {
             var environment = CommandResolverTestUtils.SetupEnvironmentProviderWhichFindsExtensions(".exe");
-            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(environment);
+            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(environment, forceGeneric: true);
 
             CommandResolverTestUtils.CreateNonRunnableTestCommand(AppContext.BaseDirectory, "appbasetestcommand1", ".exe");
 
@@ -120,7 +120,7 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
         public void It_returns_a_CommandSpec_with_Args_as_stringEmpty_when_returning_a_CommandSpec_and_CommandArguments_are_null()
         {
             var environment = CommandResolverTestUtils.SetupEnvironmentProviderWhichFindsExtensions(".exe");
-            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(environment);
+            var appBaseCommandResolver = SetupPlatformAppBaseCommandResolver(environment, forceGeneric: true);
 
             CommandResolverTestUtils.CreateNonRunnableTestCommand(AppContext.BaseDirectory, "appbasetestcommand1", ".exe");
 
@@ -161,20 +161,45 @@ namespace Microsoft.DotNet.Cli.Utils.Tests
             commandFile.Should().Be("appbasetestcommand1.exe");
         }
 
-        private AppBaseCommandResolver SetupPlatformAppBaseCommandResolver(IEnvironmentProvider environment = null)
+        public void It_wraps_command_with_CMD_EXE_when_command_has_CMD_Extension_and_using_WindowsExePreferredCommandSpecFactory()
+        {
+            var environment = new EnvironmentProvider(new [] {".cmd"});
+            var platformCommandSpecFactory = new WindowsExePreferredCommandSpecFactory();
+
+            var pathCommandResolver = new PathCommandResolver(environment, platformCommandSpecFactory);
+
+            var testCommandPath = 
+                CommandResolverTestUtils.CreateNonRunnableTestCommand(AppContext.BaseDirectory, "cmdWrapCommand", ".cmd");
+
+            var commandResolverArguments = new CommandResolverArguments()
+            {
+                CommandName = "cmdWrapCommand",
+                CommandArguments = null
+            };
+
+            var result = pathCommandResolver.Resolve(commandResolverArguments);
+
+            result.Should().NotBeNull();
+
+            var commandFile = Path.GetFileName(result.Path);
+            commandFile.Should().Be("cmd.exe");
+
+            result.Args.Should().Contain(testCommandPath);
+        }
+
+        private AppBaseCommandResolver SetupPlatformAppBaseCommandResolver(
+            IEnvironmentProvider environment = null,
+            bool forceGeneric = false)
         {
             environment = environment ?? new EnvironmentProvider();
 
-            var platformCommandSpecFactory = default(IPlatformCommandSpecFactory);
+            IPlatformCommandSpecFactory platformCommandSpecFactory  = new GenericPlatformCommandSpecFactory();
 
-            if (PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows)
+            if (PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows
+                && !forceGeneric)
             {
                 platformCommandSpecFactory = new WindowsExePreferredCommandSpecFactory();
             }
-            else
-            {
-                platformCommandSpecFactory = new GenericPlatformCommandSpecFactory();
-            }
 
             var appBaseCommandResolver = new AppBaseCommandResolver(environment, platformCommandSpecFactory);