ScimFinder to support local part email as username

ee/app/finders/scim_finder.rb

@@ -73,10 +73,22 @@ class ScimFinder
   end
 
   def by_username(username)
-    user = User.find_by_username(username) || User.find_by_any_email(username)
+    user = User.find_by_username(username)
+
+    if !user && email?(username)
+      user ||= User.find_by_any_email(username) || User.find_by_username(email_local_part(username))
+    end
 
     return group.scim_identities.for_user(user) if scim_identities_enabled?
 
     saml_provider.identities.for_user(user)
   end
+
+  def email?(email)
+    ::ValidateEmail.valid?(email)
+  end
+
+  def email_local_part(email)
+    ::Mail::Address.new(email).local
+  end
 end

ee/changelogs/233139-scim_finder_to_support_email_fragment_as_username.yml

+---
+title: SCIM get users API to search for email fragment as username
+merge_request: 38807
+author:
+type: changed

ee/spec/finders/scim_finder_spec.rb

@@ -3,7 +3,7 @@
 require 'spec_helper'
 
 RSpec.describe ScimFinder do
-  let(:group) { create(:group) }
+  let_it_be(:group) { create(:group) }
   let(:unused_params) { double }
 
   subject(:finder) { described_class.new(group) }
@@ -42,7 +42,7 @@ RSpec.describe ScimFinder do
     end
 
     context 'with SCIM enabled' do
-      let!(:saml_provider) { create(:saml_provider, group: group) }
+      let_it_be(:saml_provider) { create(:saml_provider, group: group) }
 
       context 'with an eq filter' do
         shared_examples 'valid lookups' do
@@ -57,10 +57,15 @@ RSpec.describe ScimFinder do
           end
 
           context 'allows lookup by userName' do
-            it 'finds user when userName is an email address' do
+            it 'finds user by an email address' do
               expect(finder.search(filter: "userName eq #{id.user.email}").first).to eq id
             end
 
+            it 'finds user by using local part of email address as username' do
+              email = "#{id.user.username}@example.com"
+              expect(finder.search(filter: "userName eq #{email}").first).to eq id
+            end
+
             it 'finds user by username' do
               expect(finder.search(filter: "userName eq \"#{id.user.username}\"").first).to eq id
             end
@@ -75,7 +80,7 @@ RSpec.describe ScimFinder do
           before do
             stub_feature_flags(scim_identities: false)
           end
-          let(:id) { create(:group_saml_identity, saml_provider: saml_provider) }
+          let_it_be(:id) { create(:group_saml_identity, saml_provider: saml_provider) }
 
           it_behaves_like 'valid lookups'
         end
@@ -84,7 +89,8 @@ RSpec.describe ScimFinder do
           before do
             stub_feature_flags(scim_identities: true)
           end
-          let(:id) { create(:scim_identity, group: group) }
+          let_it_be(:user) { create(:user, username: 'foo', email: 'bar@example.com') }
+          let_it_be(:id) { create(:scim_identity, group: group, user: user) }
 
           it_behaves_like 'valid lookups'
         end