Update `project` to `target_project` in approvals

**Why?**
The merge request should respect the approval rules
of the target project, not the source project.

ee/app/views/shared/issuable/_approvals.html.haml

@@ -11,7 +11,7 @@
   = form.label :approver_ids, class: 'col-form-label col-sm-2' do
     Approvers
   .col-sm-10
-    - if Feature.enabled?(:approval_rules, @project)
+    - if Feature.enabled?(:approval_rules, @target_project)
       = render 'shared/issuable/approvals_multiple_rule', issuable: issuable
     - else
       = render 'shared/issuable/approvals_single_rule', issuable: issuable, presenter: presenter, form: form

ee/app/views/shared/issuable/_approvals_multiple_rule.html.haml

-#js-mr-approvals-input{ data: { 'project_id': @project.id,
+#js-mr-approvals-input{ data: { 'project_id': @target_project.id,
   'can_edit': can?(current_user, :update_approvers, issuable).to_s,
-  'allow_multi_rule': @project.multiple_approval_rules_available?.to_s,
+  'allow_multi_rule': @target_project.multiple_approval_rules_available?.to_s,
   'mr_id': issuable.iid,
-  'mr_settings_path': issuable.iid && api_v4_projects_merge_requests_approval_settings_path(id: @project.id, merge_request_iid: issuable.iid),
-  'project_settings_path': api_v4_projects_approval_settings_path(id: @project.id) } }
+  'mr_settings_path': issuable.iid && api_v4_projects_merge_requests_approval_settings_path(id: @target_project.id, merge_request_iid: issuable.iid),
+  'project_settings_path': api_v4_projects_approval_settings_path(id: @target_project.id) } }
   = sprite_icon('spinner', size: 24, css_class: 'gl-spinner')

ee/changelogs/unreleased/10601-merge-request-creation-from-fork-fails-due-to-approval-rule-sourcing.yml

+---
+title: Fix approval rule sourcing from forked MR
+merge_request: 10474
+author:
+type: fixed

ee/spec/features/merge_request/user_sets_approval_rules_spec.rb

@@ -3,10 +3,16 @@
 require 'rails_helper'
 
 describe 'Merge request > User sets approval rules', :js do
+  include ProjectForksHelper
+
   let(:approver) { create(:user) }
   let(:author) { create(:user) }
   let(:project) { create(:project, :public, :repository) }
 
+  def page_rule_names
+    page.all('.js-approval-rules table .js-name')
+  end
+
   before do
     stub_licensed_features(multiple_approval_rules: true)
 
@@ -16,12 +22,36 @@ describe 'Merge request > User sets approval rules', :js do
   end
 
   context "with project approval rules" do
-    let!(:regular_rule) { create(:approval_project_rule, project: project, users: [approver], name: 'Regular Rule') }
+    let!(:regular_rules) do
+      Array.new(3) do |i|
+        create(:approval_project_rule, project: project, users: [approver], name: "Regular Rule #{i}")
+      end
+    end
+
+    context "from a fork" do
+      let(:forked_project) { fork_project(project, nil, repository: true) }
+
+      before do
+        forked_project.add_maintainer(author)
+        allow(forked_project).to receive(:multiple_approval_rules_available?).and_return(false)
+
+        sign_in(author)
+        visit project_new_merge_request_path(forked_project, merge_request: { target_branch: 'master', target_project_id: project.id, source_branch: 'feature' })
+        wait_for_requests
+      end
+
+      it "shows approval rules from target project" do
+        names = page_rule_names
+        regular_rules.each_with_index do |rule, idx|
+          expect(names[idx]).to have_text(rule.name)
+        end
+      end
+    end
 
     context "with a private group rule" do
       let!(:private_group) { create(:group, :private) }
       let!(:private_rule) { create(:approval_project_rule, project: project, groups: [private_group], name: 'Private Rule') }
-      let!(:rules) { [regular_rule, private_rule] }
+      let!(:rules) { regular_rules + [private_rule] }
 
       before do
         private_group.add_developer(approver)
@@ -32,7 +62,7 @@ describe 'Merge request > User sets approval rules', :js do
       end
 
       it "shows approval rules" do
-        names = page.all('.js-approval-rules table .js-name')
+        names = page_rule_names
         rules.each.with_index do |rule, idx|
           expect(names[idx]).to have_text(rule.name)
         end

spec/views/projects/merge_requests/creations/_new_submit.html.haml_spec.rb

@@ -12,6 +12,7 @@ describe 'projects/merge_requests/creations/_new_submit.html.haml' do
     assign(:hidden_commit_count, 0)
     assign(:total_commit_count, merge_request.commits.count)
     assign(:project, merge_request.target_project)
+    assign(:target_project, merge_request.target_project)
     assign(:mr_presenter, merge_request.present(current_user: merge_request.author))
 
     allow(view).to receive(:can?).and_return(true)

spec/views/projects/merge_requests/edit.html.haml_spec.rb

@@ -23,6 +23,7 @@ describe 'projects/merge_requests/edit.html.haml' do
 
   before do
     assign(:project, project)
+    assign(:target_project, project)
     assign(:merge_request, closed_merge_request)
     assign(:mr_presenter, closed_merge_request.present(current_user: user))