Add ISystemPrompts component and impl for Windows

Introduce the `ISystemPrompts` component which provides native/system UI
prompts, starting with basic credential prompts. Include a basic
implementation for Windows.

src/shared/Microsoft.Git.CredentialManager.Tests/Authentication/BasicAuthenticationTests.cs

@@ -3,6 +3,7 @@
 using System;
 using Microsoft.Git.CredentialManager.Authentication;
 using Microsoft.Git.CredentialManager.Tests.Objects;
+using Moq;
 using Xunit;
 
 namespace Microsoft.Git.CredentialManager.Tests.Authentication
@@ -19,49 +20,50 @@ public void BasicAuthentication_GetCredentials_NullResource_ThrowsException()
         }
 
         [Fact]
-        public void BasicAuthentication_GetCredentials_ResourceAndUserName_PasswordPromptReturnsCredentials()
+        public void BasicAuthentication_GetCredentials_NonDesktopSession_ResourceAndUserName_PasswordPromptReturnsCredentials()
         {
             const string testResource = "https://example.com";
             const string testUserName = "john.doe";
             const string testPassword = "letmein123";
 
-            var context = new TestCommandContext();
+            var context = new TestCommandContext {IsDesktopSession = false};
             context.Terminal.SecretPrompts["Password"] = testPassword;
 
             var basicAuth = new BasicAuthentication(context);
 
-            GitCredential credential = basicAuth.GetCredentials(testResource, testUserName);
+            ICredential credential = basicAuth.GetCredentials(testResource, testUserName);
 
             Assert.Equal(testUserName, credential.UserName);
             Assert.Equal(testPassword, credential.Password);
         }
 
         [Fact]
-        public void BasicAuthentication_GetCredentials_Resource_UserPassPromptReturnsCredentials()
+        public void BasicAuthentication_GetCredentials_NonDesktopSession_Resource_UserPassPromptReturnsCredentials()
         {
             const string testResource = "https://example.com";
             const string testUserName = "john.doe";
             const string testPassword = "letmein123";
 
-            var context = new TestCommandContext();
+            var context = new TestCommandContext {IsDesktopSession = false};
             context.Terminal.Prompts["Username"] = testUserName;
             context.Terminal.SecretPrompts["Password"] = testPassword;
 
             var basicAuth = new BasicAuthentication(context);
 
-            GitCredential credential = basicAuth.GetCredentials(testResource);
+            ICredential credential = basicAuth.GetCredentials(testResource);
 
             Assert.Equal(testUserName, credential.UserName);
             Assert.Equal(testPassword, credential.Password);
         }
 
         [Fact]
-        public void BasicAuthentication_GetCredentials_NoInteraction_ThrowsException()
+        public void BasicAuthentication_GetCredentials_NonDesktopSession_NoTerminalPrompts_ThrowsException()
         {
             const string testResource = "https://example.com";
 
             var context = new TestCommandContext
             {
+                IsDesktopSession = false,
                 Settings = {IsInteractionAllowed = false},
             };
 
@@ -70,19 +72,98 @@ public void BasicAuthentication_GetCredentials_NoInteraction_ThrowsException()
             Assert.Throws<InvalidOperationException>(() => basicAuth.GetCredentials(testResource));
         }
 
-        [Fact]
-        public void BasicAuthentication_GetCredentials_NoTerminalPrompts_ThrowsException()
+        [PlatformFact(Platform.Windows)]
+        public void BasicAuthentication_GetCredentials_DesktopSession_Resource_UserPassPromptReturnsCredentials()
         {
             const string testResource = "https://example.com";
+            const string testUserName = "john.doe";
+            const string testPassword = "letmein123";
 
             var context = new TestCommandContext
             {
-                Settings = {IsTerminalPromptsEnabled = false},
+                IsDesktopSession = true,
+                SystemPrompts =
+                {
+                    CredentialPrompt = (resource, userName) =>
+                    {
+                        Assert.Equal(testResource, resource);
+                        Assert.Null(userName);
+
+                        return new GitCredential(testUserName, testPassword);
+                    }
+                }
             };
 
             var basicAuth = new BasicAuthentication(context);
 
-            Assert.Throws<InvalidOperationException>(() => basicAuth.GetCredentials(testResource));
+            ICredential credential = basicAuth.GetCredentials(testResource);
+
+            Assert.NotNull(credential);
+            Assert.Equal(testUserName, credential.UserName);
+            Assert.Equal(testPassword, credential.Password);
+        }
+
+        [PlatformFact(Platform.Windows)]
+        public void BasicAuthentication_GetCredentials_DesktopSession_ResourceAndUser_PassPromptReturnsCredentials()
+        {
+            const string testResource = "https://example.com";
+            const string testUserName = "john.doe";
+            const string testPassword = "letmein123";
+
+            var context = new TestCommandContext
+            {
+                IsDesktopSession = true,
+                SystemPrompts =
+                {
+                    CredentialPrompt = (resource, userName) =>
+                    {
+                        Assert.Equal(testResource, resource);
+                        Assert.Equal(testUserName, userName);
+
+                        return new GitCredential(testUserName, testPassword);
+                    }
+                }
+            };
+
+            var basicAuth = new BasicAuthentication(context);
+
+            ICredential credential = basicAuth.GetCredentials(testResource, testUserName);
+
+            Assert.NotNull(credential);
+            Assert.Equal(testUserName, credential.UserName);
+            Assert.Equal(testPassword, credential.Password);
+        }
+
+        [PlatformFact(Platform.Windows)]
+        public void BasicAuthentication_GetCredentials_DesktopSession_ResourceAndUser_PassPromptDiffUserReturnsCredentials()
+        {
+            const string testResource = "https://example.com";
+            const string testUserName = "john.doe";
+            const string newUserName  = "jane.doe";
+            const string testPassword = "letmein123";
+
+            var context = new TestCommandContext
+            {
+                IsDesktopSession = true,
+                SystemPrompts =
+                {
+                    CredentialPrompt = (resource, userName) =>
+                    {
+                        Assert.Equal(testResource, resource);
+                        Assert.Equal(testUserName, userName);
+
+                        return new GitCredential(newUserName, testPassword);
+                    }
+                }
+            };
+
+            var basicAuth = new BasicAuthentication(context);
+
+            ICredential credential = basicAuth.GetCredentials(testResource, testUserName);
+
+            Assert.NotNull(credential);
+            Assert.Equal(newUserName, credential.UserName);
+            Assert.Equal(testPassword, credential.Password);
         }
     }
 }

src/shared/Microsoft.Git.CredentialManager.Tests/Interop/Windows/WindowsSystemPromptsTests.cs

@@ -0,0 +1,31 @@
+using System;
+using Microsoft.Git.CredentialManager.Interop.Windows;
+using Microsoft.Git.CredentialManager.Tests.Objects;
+using Xunit;
+
+namespace Microsoft.Git.CredentialManager.Tests.Interop.Windows
+{
+    public class WindowsSystemPromptsTests
+    {
+        [Fact]
+        public void WindowsSystemPrompts_ShowCredentialPrompt_NullResource_ThrowsException()
+        {
+            var sysPrompts = new WindowsSystemPrompts();
+            Assert.Throws<ArgumentNullException>(() => sysPrompts.ShowCredentialPrompt(null, null, out _));
+        }
+
+        [Fact]
+        public void WindowsSystemPrompts_ShowCredentialPrompt_EmptyResource_ThrowsException()
+        {
+            var sysPrompts = new WindowsSystemPrompts();
+            Assert.Throws<ArgumentException>(() => sysPrompts.ShowCredentialPrompt(string.Empty, null, out _));
+        }
+
+        [Fact]
+        public void WindowsSystemPrompts_ShowCredentialPrompt_WhiteSpaceResource_ThrowsException()
+        {
+            var sysPrompts = new WindowsSystemPrompts();
+            Assert.Throws<ArgumentException>(() => sysPrompts.ShowCredentialPrompt("   ", null, out _));
+        }
+    }
+}

src/shared/Microsoft.Git.CredentialManager/Authentication/BasicAuthentication.cs

@@ -1,16 +1,17 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
+using System;
 
 namespace Microsoft.Git.CredentialManager.Authentication
 {
     public interface IBasicAuthentication
     {
-        GitCredential GetCredentials(string resource, string userName);
+        ICredential GetCredentials(string resource, string userName);
     }
 
     public static class BasicAuthenticationExtensions
     {
-        public static GitCredential GetCredentials(this IBasicAuthentication basicAuth, string resource)
+        public static ICredential GetCredentials(this IBasicAuthentication basicAuth, string resource)
         {
             return basicAuth.GetCredentials(resource, null);
         }
@@ -26,13 +27,25 @@ public class BasicAuthentication : AuthenticationBase, IBasicAuthentication
         public BasicAuthentication(ICommandContext context)
             : base (context) { }
 
-        public GitCredential GetCredentials(string resource, string userName)
+        public ICredential GetCredentials(string resource, string userName)
         {
             EnsureArgument.NotNullOrWhiteSpace(resource, nameof(resource));
 
             ThrowIfUserInteractionDisabled();
+
+            // TODO: we only support system GUI prompts on Windows currently
+            if (Context.IsDesktopSession && PlatformUtils.IsWindows())
+            {
+                return GetCredentialsByUi(resource, userName);
+            }
+
             ThrowIfTerminalPromptsDisabled();
 
+            return GetCredentialsByTty(resource, userName);
+        }
+
+        private ICredential GetCredentialsByTty(string resource, string userName)
+        {
             Context.Terminal.WriteLine("Enter basic credentials for '{0}':", resource);
 
             if (!string.IsNullOrWhiteSpace(userName))
@@ -51,5 +64,15 @@ public GitCredential GetCredentials(string resource, string userName)
 
             return new GitCredential(userName, password);
         }
+
+        private ICredential GetCredentialsByUi(string resource, string userName)
+        {
+            if (!Context.SystemPrompts.ShowCredentialPrompt(resource, userName, out ICredential credential))
+            {
+                throw new Exception("User cancelled the authentication prompt.");
+            }
+
+            return credential;
+        }
     }
 }

src/shared/Microsoft.Git.CredentialManager/Authentication/MicrosoftAuthentication.cs

@@ -129,7 +129,7 @@ private async Task<JsonWebToken> GetAccessTokenInProcAsync(string authority, str
                 }
 #elif NETSTANDARD
                 // MSAL requires the application redirect URI is a loopback address to use the System WebView
-                if (PlatformUtils.IsDesktopSession() && app.IsSystemWebViewAvailable && redirectUri.IsLoopback)
+                if (Context.IsDesktopSession && app.IsSystemWebViewAvailable && redirectUri.IsLoopback)
                 {
                     result = await app.AcquireTokenInteractive(scopes)
                         .WithPrompt(Prompt.SelectAccount)

src/shared/Microsoft.Git.CredentialManager/CommandContext.cs

@@ -28,6 +28,11 @@ public interface ICommandContext : IDisposable
         /// </summary>
         ITerminal Terminal { get; }
 
+        /// <summary>
+        /// Returns true if in a GUI session/desktop is available, false otherwise.
+        /// </summary>
+        bool IsDesktopSession { get; }
+
         /// <summary>
         /// Application tracing system.
         /// </summary>
@@ -57,6 +62,11 @@ public interface ICommandContext : IDisposable
         /// The current process environment.
         /// </summary>
         IEnvironment Environment { get; }
+
+        /// <summary>
+        /// Native UI prompts.
+        /// </summary>
+        ISystemPrompts SystemPrompts { get; }
     }
 
     /// <summary>
@@ -76,13 +86,15 @@ public CommandContext()
                 Environment     = new WindowsEnvironment(FileSystem);
                 Terminal        = new WindowsTerminal(Trace);
                 CredentialStore = WindowsCredentialManager.Open();
+                SystemPrompts   = new WindowsSystemPrompts();
             }
             else if (PlatformUtils.IsPosix())
             {
                 if (PlatformUtils.IsMacOS())
                 {
                     FileSystem      = new MacOSFileSystem();
                     CredentialStore = MacOSKeychain.Open();
+                    SystemPrompts   = new MacOSSystemPrompts();
                 }
                 else if (PlatformUtils.IsLinux())
                 {
@@ -96,6 +108,7 @@ public CommandContext()
             string repoPath   = Git.GetRepositoryPath(FileSystem.GetCurrentDirectory());
             Settings          = new Settings(Environment, Git, repoPath);
             HttpClientFactory = new HttpClientFactory(Trace, Settings, Streams);
+            IsDesktopSession  = PlatformUtils.IsDesktopSession();
         }
 
         #region ICommandContext
@@ -106,6 +119,8 @@ public CommandContext()
 
         public ITerminal Terminal { get; }
 
+        public bool IsDesktopSession { get; }
+
         public ITrace Trace { get; }
 
         public IFileSystem FileSystem { get; }
@@ -118,6 +133,8 @@ public CommandContext()
 
         public IEnvironment Environment { get; }
 
+        public ISystemPrompts SystemPrompts { get; }
+
         #endregion
 
         #region IDisposable

src/shared/Microsoft.Git.CredentialManager/ISystemPrompts.cs

@@ -0,0 +1,10 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+namespace Microsoft.Git.CredentialManager
+{
+    public interface ISystemPrompts
+    {
+        bool ShowCredentialPrompt(string resource, string userName, out ICredential credential);
+    }
+}

src/shared/Microsoft.Git.CredentialManager/Interop/MacOS/MacOSSystemPrompts.cs

@@ -0,0 +1,13 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+namespace Microsoft.Git.CredentialManager.Interop.MacOS
+{
+    public class MacOSSystemPrompts : ISystemPrompts
+    {
+        public bool ShowCredentialPrompt(string resource, string userName, out ICredential credential)
+        {
+            throw new System.NotImplementedException();
+        }
+    }
+}

src/shared/Microsoft.Git.CredentialManager/Interop/Windows/Native/Advapi32.cs

@@ -1,6 +1,5 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
-
 using System;
 using System.Runtime.InteropServices;
 using System.Runtime.InteropServices.ComTypes;