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

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

@@ -19,6 +19,7 @@
 using OrchardCore.Modules;
 using OrchardCore.Mvc.Core.Utilities;
 using OrchardCore.Settings;
+using OrchardCore.Users.Abstractions;
 using OrchardCore.Users.Events;
 using OrchardCore.Users.Handlers;
 using OrchardCore.Users.Models;
@@ -47,6 +48,7 @@ public class AccountController : AccountBaseController
         private readonly IClock _clock;
         private readonly IDistributedCache _distributedCache;
         private readonly IEnumerable<IExternalLoginEventHandler> _externalLoginHandlers;
+        private readonly IEnumerable<IExternalLoginUserToRelateFinder> _externalLoginUsrFinder;
 
         protected readonly IHtmlLocalizer H;
         protected readonly IStringLocalizer S;
@@ -67,7 +69,8 @@ public AccountController(
             IShellFeaturesManager shellFeaturesManager,
             IDisplayManager<LoginForm> loginFormDisplayManager,
             IUpdateModelAccessor updateModelAccessor,
-            IEnumerable<IExternalLoginEventHandler> externalLoginHandlers)
+            IEnumerable<IExternalLoginEventHandler> externalLoginHandlers,
+            IEnumerable<IExternalLoginUserToRelateFinder> externalLoginUsrFinder)
         {
             _signInManager = signInManager;
             _userManager = userManager;
@@ -83,6 +86,7 @@ public AccountController(
             _loginFormDisplayManager = loginFormDisplayManager;
             _updateModelAccessor = updateModelAccessor;
             _externalLoginHandlers = externalLoginHandlers;
+            _externalLoginUsrFinder = externalLoginUsrFinder.Reverse();
 
             H = htmlLocalizer;
             S = stringLocalizer;
@@ -384,12 +388,9 @@ public async Task<IActionResult> ExternalLoginCallback(string returnUrl = null,
             }
             else
             {
-                var email = info.Principal.FindFirstValue(ClaimTypes.Email) ?? info.Principal.FindFirstValue("email");
-
-                if (!string.IsNullOrWhiteSpace(email))
-                {
-                    iUser = await _userManager.FindByEmailAsync(email);
-                }
+                //really important the order of the services registration in the dependency injection context
+                var usrFinder = _externalLoginUsrFinder.Where(x => x.CanManageThis(info.LoginProvider)).FirstOrDefault();
+                iUser = usrFinder == null ? null : await usrFinder.FindUserToRelateAsync(info);
 
                 ViewData["ReturnUrl"] = returnUrl;
                 ViewData["LoginProvider"] = info.LoginProvider;
@@ -409,7 +410,7 @@ public async Task<IActionResult> ExternalLoginCallback(string returnUrl = null,
 
                     // Link external login to an existing user
                     ViewData["UserName"] = iUser.UserName;
-                    ViewData["Email"] = email;
+                    ViewData["LinkParameterValue"] = usrFinder?.GetValueThatLinkAccount(info);
 
                     return View(nameof(LinkExternalLogin));
                 }
@@ -423,6 +424,8 @@ public async Task<IActionResult> ExternalLoginCallback(string returnUrl = null,
                 }
                 else
                 {
+                    var email = info.Principal.FindFirstValue(ClaimTypes.Email) ?? info.Principal.FindFirstValue("email");
+
                     var externalLoginViewModel = new RegisterExternalLoginViewModel
                     {
                         NoPassword = registrationSettings.NoPasswordForExternalUsers,
@@ -630,9 +633,9 @@ 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);
+            //really important the order of the services registration in the dependency injection context
+            var usrFinder = _externalLoginUsrFinder.Where(x => x.CanManageThis(info.LoginProvider)).FirstOrDefault();
+            var user = await usrFinder?.FindUserToRelateAsync(info) ?? null;
 
             if (user == null)
             {

src/OrchardCore.Modules/OrchardCore.Users/Services/DefaultExternalLoginUserToRelateFinder.cs

@@ -0,0 +1,42 @@
+
+using System.Runtime.CompilerServices;
+using System.Security.Claims;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Identity;
+using OrchardCore.Users.Abstractions;
+
+namespace OrchardCore.Users.Services;
+
+public class DefaultExternalLoginUserToRelateFinder : IExternalLoginUserToRelateFinder
+{
+  private readonly UserManager<IUser> _userManager;
+
+  public DefaultExternalLoginUserToRelateFinder(UserManager<IUser> userManager)
+  {
+    _userManager = userManager;
+  }
+
+  public bool CanManageThis(string extLoginKind)
+  {
+    return true;
+  }
+
+  public async Task<IUser> FindUserToRelateAsync(ExternalLoginInfo info)
+  {
+    //the default behavior previously used in OrchardCore
+    var email = info.Principal.FindFirstValue(ClaimTypes.Email) ?? info.Principal.FindFirstValue("email");
+
+    IUser iUser = null;
+    if (!string.IsNullOrWhiteSpace(email))
+    {
+      iUser = await _userManager.FindByEmailAsync(email);
+    }
+
+    return iUser;
+  }
+
+  public string GetValueThatLinkAccount(ExternalLoginInfo info)
+  {
+    return info.Principal.FindFirstValue(ClaimTypes.Email) ?? info.Principal.FindFirstValue("email");
+  }
+}

src/OrchardCore.Modules/OrchardCore.Users/Startup.cs

@@ -39,6 +39,7 @@
 using OrchardCore.Settings.Deployment;
 using OrchardCore.Setup.Events;
 using OrchardCore.Sms;
+using OrchardCore.Users.Abstractions;
 using OrchardCore.Users.Commands;
 using OrchardCore.Users.Controllers;
 using OrchardCore.Users.Deployment;
@@ -198,6 +199,8 @@ public override void ConfigureServices(IServiceCollection services)
             services.AddScoped<CustomUserSettingsService>();
             services.AddRecipeExecutionStep<CustomUserSettingsStep>();
             services.AddScoped<IDisplayDriver<LoginForm>, LoginFormDisplayDriver>();
+
+            services.AddScoped<IExternalLoginUserToRelateFinder, DefaultExternalLoginUserToRelateFinder>();
         }
     }
 

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>. Seems already exist an account identificable by this information: <strong>{1}</strong>. Enter your local account password and click the Register button to link the accounts and finish logging in.", ViewData["LoginProvider"], ViewData["LinkParameterValue"]]
     </p>
     <hr />
     <div asp-validation-summary="ModelOnly"></div>
@@ -20,9 +20,9 @@
     </div>
 
     <div class="mb-3">
-        <label for="Email" class="col-md-3 form-label">@T["Email"]</label>
+        <label for="LinkParameterValue" class="col-md-3 form-label">@T["Parameter that identify an existing account"]</label>
         <div class="col-md-9">
-            <input id="Email" value="@ViewData["Email"]" class="form-control" disabled />
+            <input id="LinkParameterValue" value="@ViewData["LinkParameterValue"]" class="form-control" disabled />
         </div>
     </div>
 

src/OrchardCore/OrchardCore.Users.Abstractions/Services/IExternalLoginUserToRelateFinder.cs

@@ -0,0 +1,14 @@
+
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Identity;
+
+namespace OrchardCore.Users.Abstractions;
+
+public interface IExternalLoginUserToRelateFinder
+{
+  bool CanManageThis(string extLoginKind);
+
+  Task<IUser> FindUserToRelateAsync(ExternalLoginInfo info);
+
+  string GetValueThatLinkAccount(ExternalLoginInfo info);
+}