Fix e-mail verification returning a 500 Errorsh-fix-email-confirmations

When a user goes to confirm an e-mail address, he/she is met with
an ugly 500 error:

```
NoMethodError (undefined method `accept_pending_invitations!' for #<Email:0x00007fae8df17578>):
  app/controllers/concerns/accepts_pending_invitations.rb:7:in `accept_pending_invitations'
  app/controllers/confirmations_controller.rb:16:in `after_confirmation_path_for'
```

This fixes a regression introduced by !17634.

Closes #49252

4 files changed, 54 insertions, 4 deletions

diff --git a/app/controllers/confirmations_controller.rb b/app/controllers/confirmations_controller.rb
index 7bc46a6ccc0..a7200b63b7e 100644
--- a/app/controllers/confirmations_controller.rb
+++ b/app/controllers/confirmations_controller.rb
@@ -13,10 +13,9 @@ class ConfirmationsController < Devise::ConfirmationsController
   end
 
   def after_confirmation_path_for(resource_name, resource)
-    accept_pending_invitations
-
     # incoming resource can either be a :user or an :email
     if signed_in?(:user)
+      accept_pending_invitations
       after_sign_in(resource)
     else
       Gitlab::AppLogger.info("Email Confirmed: username=#{resource.username} email=#{resource.email} ip=#{request.remote_ip}")
diff --git a/changelogs/unreleased/sh-fix-email-confirmations.yml b/changelogs/unreleased/sh-fix-email-confirmations.yml
new file mode 100644
index 00000000000..6472dbc4479
--- /dev/null
+++ b/changelogs/unreleased/sh-fix-email-confirmations.yml
@@ -0,0 +1,5 @@
+---
+title: Fix e-mail verification returning a 500 Error
+merge_request: 20838
+author:
+type: fixed
diff --git a/spec/controllers/confirmations_controller_spec.rb b/spec/controllers/confirmations_controller_spec.rb
new file mode 100644
index 00000000000..e530b7d6dc5
--- /dev/null
+++ b/spec/controllers/confirmations_controller_spec.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe ConfirmationsController do
+  include DeviseHelpers
+
+  describe 'GET #show' do
+    context 'with user' do
+      let(:token) { '123456' }
+      let(:user) { create(:user, confirmation_token: token, unconfirmed_email: 'test@example.com', confirmation_sent_at: Time.now, confirmed_at: nil) }
+
+      before do
+        set_devise_mapping(context: @request)
+      end
+
+      it 'confirms user' do
+        expect(user.confirmed?).to be_falsey
+
+        get :show, confirmation_token: token
+
+        expect(user.reload.confirmed?).to be_truthy
+        expect(response).to have_http_status(302)
+      end
+    end
+
+    context 'with e-mail' do
+      let(:token) { '987654' }
+      let(:user) { create(:user) }
+      let(:email) { create(:email, user: user, confirmation_token: token, confirmation_sent_at: Time.now, confirmed_at: nil) }
+
+      before do
+        set_devise_mapping(context: @request, resource: :email)
+      end
+
+      it 'confirms email' do
+        expect(email.confirmed?).to be_falsey
+
+        get :show, confirmation_token: token
+
+        expect(email.reload.confirmed?).to be_truthy
+        expect(response).to have_http_status(302)
+      end
+    end
+  end
+end
diff --git a/spec/support/helpers/devise_helpers.rb b/spec/support/helpers/devise_helpers.rb
index 66874e10f38..f321e68fb7e 100644
--- a/spec/support/helpers/devise_helpers.rb
+++ b/spec/support/helpers/devise_helpers.rb
@@ -1,10 +1,10 @@
 module DeviseHelpers
   # explicitly tells Devise which mapping to use
   # this is needed when we are testing a Devise controller bypassing the router
-  def set_devise_mapping(context:)
+  def set_devise_mapping(context:, resource: :user)
     env = env_from_context(context)
 
-    env['devise.mapping'] = Devise.mappings[:user] if env
+    env['devise.mapping'] = Devise.mappings[resource] if env
   end
 
   def env_from_context(context)