return a frozen account chain

so that we can return the same one every time if called multiple times
for the same context

Change-Id: I2c5825ab115c50d1332d05d1e3cecbe45cbe7ea1
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/270297
Reviewed-by: Jacob Burroughs <jburroughs@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>

app/controllers/outcome_groups_api_controller.rb

@@ -365,9 +365,9 @@ class OutcomeGroupsApiController < ApplicationController
 
     account_chain =
       if @context.is_a?(Account)
-        @context.account_chain - [@context]
+        @context.account_chain[1..]
       else
-        @context.account.account_chain
+        @context.account.account_chain.dup
       end
     account_chain.map! {|a| {
         :id => a.root_outcome_group.id,

app/models/account.rb

@@ -999,10 +999,11 @@ class Account < ActiveRecord::Base
   end
 
   def account_chain(include_site_admin: false)
-    @account_chain ||= Account.account_chain(self)
-    result = @account_chain.dup
-    Account.add_site_admin_to_chain!(result) if include_site_admin
-    result
+    @account_chain ||= Account.account_chain(self).freeze
+    if include_site_admin
+      return @account_chain_with_site_admin ||= Account.add_site_admin_to_chain!(@account_chain.dup).freeze
+    end
+    @account_chain
   end
 
   def account_chain_ids
@@ -1365,7 +1366,7 @@ class Account < ActiveRecord::Base
   end
 
   def reload(*)
-    @account_chain = nil
+    @account_chain = @account_chain_with_site_admin = nil
     super
   end
 

app/models/course.rb

@@ -1430,6 +1430,11 @@ class Course < ActiveRecord::Base
     workflow_state
   end
 
+  def reload(*)
+    @account_chain = @account_chain_with_site_admin = nil
+    super
+  end
+
   alias destroy_permanently! destroy
   def destroy
     return false if template?
@@ -1850,10 +1855,11 @@ class Course < ActiveRecord::Base
   end
 
   def account_chain(include_site_admin: false)
-    @account_chain ||= Account.account_chain(account_id)
-    result = @account_chain.dup
-    Account.add_site_admin_to_chain!(result) if include_site_admin
-    result
+    @account_chain ||= Account.account_chain(account_id).freeze
+    if include_site_admin
+      return @account_chain_with_site_admin ||= Account.add_site_admin_to_chain!(@account_chain.dup).freeze
+    end
+    @account_chain
   end
 
   def account_chain_ids

app/models/lti/message_handler.rb

@@ -83,9 +83,10 @@ module Lti
                                                             resource_type_code: resource_type_code,
                                                             context: context)
       resource_handler = nil
-      search_contexts = context.account_chain.unshift(context)
+      search_contexts = context.account_chain.dup.unshift(context)
       search_contexts.each do |search_context|
         break if resource_handler.present?
+
         resource_handler = possible_handlers.find { |rh| rh.tool_proxy.context == search_context }
       end
       resource_handler&.find_message_by_type(message_type)

app/models/role_override.rb

@@ -1634,7 +1634,6 @@ class RoleOverride < ActiveRecord::Base
 
       preloaded_overrides ||= preload_overrides(context, [role], role_context)
 
-      accounts.reverse!
       overrides = {}
 
       dummies = RequestCache.cache('role_override_dummies') do
@@ -1647,7 +1646,7 @@ class RoleOverride < ActiveRecord::Base
       preloaded_overrides.each do |(permission, overrides_by_account)|
         next if only_permission && permission != only_permission
 
-        overrides[permission] = accounts.map do |account|
+        overrides[permission] = accounts.reverse_each.map do |account|
           overrides_by_account[account.global_id].find { |ro| ro.role_id == role.id } || dummies[account.id]
         end
       end

lib/brand_config_helpers.rb

@@ -36,13 +36,13 @@ module BrandConfigHelpers
     brand_config_chain(include_self: false).find(&:brand_config_md5).try(:brand_config)
   end
 
+  private
+
   def brand_config_chain(include_self:)
-    chain = self.account_chain(include_site_admin: true)
+    chain = self.account_chain(include_site_admin: true).dup
     chain.shift unless include_self
-    chain.select!{ |a| a.shard == self.shard }
+    chain.select! { |a| a.shard == self.shard }
     ActiveRecord::Associations::Preloader.new.preload(chain, :root_account)
     chain
   end
-  private :brand_config_chain
-
 end

lib/feature_flags.rb

@@ -110,7 +110,7 @@ module FeatureFlags
     RequestCache.cache('feature_flag_account_ids', self) do
       shard.activate do
         cache.fetch(['feature_flag_account_ids', self].cache_key) do
-          chain = account_chain(include_site_admin: true)
+          chain = account_chain(include_site_admin: true).dup
           chain.shift if is_a?(Account)
           chain.reverse.map(&:global_id)
         end

spec/models/account_spec.rb

@@ -2099,6 +2099,7 @@ describe Account do
         au = AccountUser.create!(:account => other_account, :user => @user)
         expect(cached_account_users).to eq []
         @account.update_attribute(:parent_account, other_account)
+        @account.reload
         expect(cached_account_users).to eq [au]
       end