Ensure Rake DB create doesn't fail when LDAP is enabled

In EE, when LDAP is enabled GitLab will try to determine
whether multiple LDAP servers are supported on initialization.
When Rake is trying to create a database for the first time,
this attempt to look at a licensed feature caused a failure. Now
this license lookup will fail silently.

changelogs/unreleased/dblessing_ldap_rake_db_create_fix.yml

+---
+title: Ensure Rake DB create doesn't fail when LDAP is enabled
+merge_request: 51132
+author:
+type: fixed

config/initializers/8_devise.rb

@@ -232,7 +232,7 @@ Devise.setup do |config|
   end
 
   if Gitlab::Auth::Ldap::Config.enabled?
-    Gitlab::Auth::Ldap::Config.providers.each do |provider|
+    Gitlab::Auth::Ldap::Config.available_providers.each do |provider|
       ldap_config = Gitlab::Auth::Ldap::Config.new(provider)
       config.omniauth(provider, ldap_config.omniauth_options)
     end

ee/lib/ee/gitlab/auth/ldap/config.rb

@@ -17,6 +17,9 @@ module EE
             override :_available_servers
             def _available_servers
               ::License.feature_available?(:multiple_ldap_servers) ? servers : super
+            rescue ActiveRecord::NoDatabaseError
+              # Rake is probably trying to initialize the DB
+              []
             end
           end
         end

ee/spec/lib/ee/gitlab/auth/ldap/config_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Auth::Ldap::Config do
+  include LdapHelpers
+
+  describe '.available_providers' do
+    before do
+      stub_ldap_setting(
+        'enabled' => true,
+        'servers' => {
+          'main'      => { 'provider_name' => 'ldapmain' },
+          'secondary' => { 'provider_name' => 'ldapsecondary' }
+        }
+      )
+    end
+
+    context 'when multiple LDAP servers are licensed' do
+      before do
+        stub_licensed_features(multiple_ldap_servers: true)
+      end
+
+      it 'returns multiple configured providers' do
+        expect(described_class.available_providers).to match_array(%w(ldapmain ldapsecondary))
+      end
+    end
+  end
+
+  describe '._available_servers' do
+    context 'when no database connection occurs' do
+      before do
+        allow(::License).to receive(:feature_available?).and_raise(ActiveRecord::NoDatabaseError)
+      end
+
+      it 'returns an empty array' do
+        expect(described_class._available_servers).to eq([])
+      end
+    end
+  end
+end

lib/gitlab/auth/ldap/config.rb

@@ -28,7 +28,7 @@ module Gitlab
         end
 
         def self.servers
-          Gitlab.config.ldap['servers']&.values || []
+          Gitlab.config.ldap.servers&.values || []
         end
 
         def self.available_servers
@@ -42,9 +42,18 @@ module Gitlab
         end
 
         def self.providers
-          servers.map { |server| server['provider_name'] }
+          provider_names_from_servers(servers)
         end
 
+        def self.available_providers
+          provider_names_from_servers(available_servers)
+        end
+
+        def self.provider_names_from_servers(servers)
+          servers&.map { |server| server['provider_name'] } || []
+        end
+        private_class_method :provider_names_from_servers
+
         def self.valid_provider?(provider)
           providers.include?(provider)
         end

spec/lib/gitlab/auth/ldap/config_spec.rb

@@ -5,6 +5,10 @@ require 'spec_helper'
 RSpec.describe Gitlab::Auth::Ldap::Config do
   include LdapHelpers
 
+  before do
+    stub_ldap_setting(enabled: true)
+  end
+
   let(:config) { described_class.new('ldapmain') }
 
   def raw_cert
@@ -68,12 +72,28 @@ AtlErSqafbECNDSwS5BX8yDpu5yRBJ4xegO/rNlmb8ICRYkuJapD1xXicFOsmfUK
 
   describe '.servers' do
     it 'returns empty array if no server information is available' do
-      allow(Gitlab.config).to receive(:ldap).and_return('enabled' => false)
+      stub_ldap_setting(servers: {})
 
       expect(described_class.servers).to eq []
     end
   end
 
+  describe '.available_providers' do
+    before do
+      stub_licensed_features(multiple_ldap_servers: false)
+      stub_ldap_setting(
+        'servers' => {
+          'main' => { 'provider_name' => 'ldapmain' },
+          'secondary' => { 'provider_name' => 'ldapsecondary' }
+        }
+      )
+    end
+
+    it 'returns one provider' do
+      expect(described_class.available_providers).to match_array(%w(ldapmain))
+    end
+  end
+
   describe '#initialize' do
     it 'requires a provider' do
       expect { described_class.new }.to raise_error ArgumentError