Implement a default service to link local user accounts with external ones during the registration process

src/OrchardCore.Modules/OrchardCore.Users/Controllers/AccountController.cs

@@ -2,7 +2,6 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Security.Claims;
-using System.Text.Json;
 using System.Text.Json.Nodes;
 using System.Text.Json.Settings;
 using System.Threading.Tasks;
@@ -15,6 +14,7 @@
 using Microsoft.Extensions.Caching.Distributed;
 using Microsoft.Extensions.Localization;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
 using Microsoft.IdentityModel.Tokens;
 using OrchardCore.ContentManagement;
 using OrchardCore.DisplayManagement;
@@ -52,7 +52,7 @@ public class AccountController : AccountBaseController
         private readonly IClock _clock;
         private readonly IDistributedCache _distributedCache;
         private readonly IEnumerable<IExternalLoginEventHandler> _externalLoginHandlers;
-
+        private readonly IdentityOptions _identityOptions;
         private static readonly JsonMergeSettings _jsonMergeSettings = new()
         {
             MergeArrayHandling = MergeArrayHandling.Replace,
@@ -78,7 +78,8 @@ public class AccountController : AccountBaseController
             IShellFeaturesManager shellFeaturesManager,
             IDisplayManager<LoginForm> loginFormDisplayManager,
             IUpdateModelAccessor updateModelAccessor,
-            IEnumerable<IExternalLoginEventHandler> externalLoginHandlers)
+            IEnumerable<IExternalLoginEventHandler> externalLoginHandlers,
+            IOptions<IdentityOptions> identityOptions)
         {
             _signInManager = signInManager;
             _userManager = userManager;
@@ -94,6 +95,7 @@ public class AccountController : AccountBaseController
             _loginFormDisplayManager = loginFormDisplayManager;
             _updateModelAccessor = updateModelAccessor;
             _externalLoginHandlers = externalLoginHandlers;
+            _identityOptions = identityOptions.Value;
 
             H = htmlLocalizer;
             S = stringLocalizer;
@@ -296,7 +298,6 @@ public async Task<IActionResult> ChangePassword(ChangePasswordViewModel model, s
         public IActionResult ChangePasswordConfirmation()
             => View();
 
-
         [HttpPost]
         [AllowAnonymous]
         [ValidateAntiForgeryToken]
@@ -316,7 +317,7 @@ private async Task<SignInResult> ExternalLoginSignInAsync(IUser user, ExternalLo
             var userInfo = user as User;
 
             var context = new UpdateUserContext(user, info.LoginProvider, externalClaims, userInfo.Properties)
-            { 
+            {
                 UserClaims = userInfo.UserClaims,
                 UserRoles = userRoles,
             };
@@ -402,9 +403,9 @@ public async Task<IActionResult> ExternalLoginCallback(string returnUrl = null,
             }
             else
             {
-                var email = info.Principal.FindFirstValue(ClaimTypes.Email) ?? info.Principal.FindFirstValue("email");
+                var email = info.GetEmail();
 
-                if (!string.IsNullOrWhiteSpace(email))
+                if (_identityOptions.User.RequireUniqueEmail && !string.IsNullOrWhiteSpace(email))
                 {
                     iUser = await _userManager.FindByEmailAsync(email);
                 }
@@ -427,7 +428,6 @@ public async Task<IActionResult> ExternalLoginCallback(string returnUrl = null,
 
                     // Link external login to an existing user
                     ViewData["UserName"] = iUser.UserName;
-                    ViewData["Email"] = email;
 
                     return View(nameof(LinkExternalLogin));
                 }
@@ -449,7 +449,7 @@ public async Task<IActionResult> ExternalLoginCallback(string returnUrl = null,
 
                         // If registrationSettings.NoUsernameForExternalUsers is true, this username will not be used
                         UserName = await GenerateUsernameAsync(info),
-                        Email = email
+                        Email = info.GetEmail(),
                     };
 
                     // The user doesn't exist and no information required, we can create the account locally
@@ -648,9 +648,8 @@ public async Task<IActionResult> LinkExternalLogin(LinkExternalLoginViewModel mo
 
                 return NotFound();
             }
-            var email = info.Principal.FindFirstValue(ClaimTypes.Email) ?? info.Principal.FindFirstValue("email");
 
-            var user = await _userManager.FindByEmailAsync(email);
+            var user = await _userManager.FindByEmailAsync(info.GetEmail());
 
             if (user == null)
             {

src/OrchardCore.Modules/OrchardCore.Users/Views/Account/LinkExternalLogin.cshtml

@@ -7,7 +7,7 @@
 <form asp-controller="Account" asp-action="LinkExternalLogin" asp-route-returnurl="@ViewData["ReturnUrl"]" method="post" class="form-horizontal no-multisubmit">
     <h4>@T["Link your account."]</h4>
     <p class="text-info">
-        @T["You've successfully authenticated with <strong>{0}</strong>. You already have an account with this email address. Enter your local account password and click the Register button to link the accounts and finish logging in.", ViewData["LoginProvider"]]
+        @T["You've successfully authenticated with <strong>{0}</strong>. You already have an account that can be linked with this external login. Enter your local account password and click the Register button to link the accounts and finish logging in.", ViewData["LoginProvider"]]
     </p>
     <hr />
     <div asp-validation-summary="ModelOnly"></div>
@@ -19,13 +19,6 @@
         </div>
     </div>
 
-    <div class="mb-3">
-        <label for="Email" class="col-md-3 form-label">@T["Email"]</label>
-        <div class="col-md-9">
-            <input id="Email" value="@ViewData["Email"]" class="form-control" disabled />
-        </div>
-    </div>
-
     <div class="mb-3">
         <label asp-for="Password" class="col-md-3 form-label">@T["Password"]</label>
         <div class="col-md-9">

src/OrchardCore/OrchardCore.Users.Core/Extensions/ExternalLoginInfoExtensions.cs

@@ -0,0 +1,9 @@
+using System.Security.Claims;
+
+namespace Microsoft.AspNetCore.Identity;
+
+public static class ExternalLoginInfoExtensions
+{
+    public static string GetEmail(this ExternalLoginInfo info)
+        => info.Principal.FindFirstValue(ClaimTypes.Email) ?? info.Principal.FindFirstValue("email");
+}