Remove validation of MR level approval rules in MR

This removes `MergeRequest#validate_approval_rule_source` which
was responsible to check whether the MR level approval rules
matches the existing project level rules.

Added the validation in `ApprovalMergeRequestRule` to check if the
project of `approval_project_rule` matches the merge request's
project. This way we can ensure that the source rule should still
be in the same project.

This will make the logic simpler for the upcoming API to create
MR level approval rules.

ee/app/models/approval_merge_request_rule.rb

@@ -39,6 +39,7 @@ class ApprovalMergeRequestRule < ApplicationRecord
   alias_method :source_rule, :approval_project_rule
 
   validate :validate_approvals_required, unless: :report_approver?
+  validate :validate_approval_project_rule
 
   enum rule_type: {
     regular: 1,
@@ -123,4 +124,11 @@ class ApprovalMergeRequestRule < ApplicationRecord
       errors.add(:approvals_required, :greater_than_or_equal_to, count: approval_project_rule.approvals_required)
     end
   end
+
+  def validate_approval_project_rule
+    return if approval_project_rule.blank?
+    return if merge_request.project == approval_project_rule.project
+
+    errors.add(:approval_project_rule, 'must be for the same project')
+  end
 end

ee/app/models/ee/merge_request.rb

@@ -35,8 +35,6 @@ module EE
 
       has_many :blocked_merge_requests, through: :blocks_as_blocker
 
-      validate :validate_approval_rule_source
-
       delegate :sha, to: :head_pipeline, prefix: :head_pipeline, allow_nil: true
       delegate :sha, to: :base_pipeline, prefix: :base_pipeline, allow_nil: true
       delegate :merge_requests_author_approval?, to: :target_project, allow_nil: true
@@ -106,21 +104,6 @@ module EE
       hidden.count
     end
 
-    def validate_approval_rule_source
-      return unless approval_rules.any?
-
-      local_project_rule_ids = approval_rules.map { |rule| rule.approval_merge_request_rule_source&.approval_project_rule_id }
-      local_project_rule_ids.compact!
-
-      invalid = if new_record?
-                  local_project_rule_ids.to_set != project.visible_regular_approval_rules.pluck(:id).to_set
-                else
-                  (local_project_rule_ids - project.approval_rule_ids).present?
-                end
-
-      errors.add(:approval_rules, :invalid_sourcing_to_project_rules) if invalid
-    end
-
     def participant_approvers
       strong_memoize(:participant_approvers) do
         next [] unless approval_needed?

ee/changelogs/unreleased/12607-remove-mr-approval-rule-source-restriction.yml

+---
+title: Remove validation of MR level approval rules in merge requests
+merge_request: 14968
+author:
+type: changed

ee/spec/models/approval_merge_request_rule_spec.rb

@@ -16,6 +16,25 @@ describe ApprovalMergeRequestRule do
       expect(build(:approval_merge_request_rule, name: nil)).not_to be_valid
     end
 
+    context 'approval_project_rule is set' do
+      let(:approval_project_rule) { build(:approval_project_rule) }
+      let(:merge_request_rule) { build(:approval_merge_request_rule, merge_request: merge_request, approval_project_rule: approval_project_rule) }
+
+      context 'when project of approval_project_rule and merge request matches' do
+        let(:merge_request) { build(:merge_request, project: approval_project_rule.project) }
+
+        it 'is valid' do
+          expect(merge_request_rule).to be_valid
+        end
+      end
+
+      context 'when the project of approval_project_rule and merge request does not match' do
+        it 'is invalid' do
+          expect(merge_request_rule).to be_invalid
+        end
+      end
+    end
+
     context 'code owner rules' do
       it 'is valid' do
         expect(build(:code_owner_rule)).to be_valid

ee/spec/models/merge_request_spec.rb

@@ -50,92 +50,6 @@ describe MergeRequest do
     end
   end
 
-  describe 'approval_rules' do
-    before do
-      stub_licensed_features(multiple_approval_rules: true)
-    end
-
-    context 'when project contains approval_rules' do
-      let!(:project_rule1) {  project.approval_rules.create(name: 'p1') }
-      let!(:project_rule2) {  project.approval_rules.create(name: 'p2') }
-
-      context "when creating" do
-        subject(:merge_request) { build(:merge_request, source_project: project, target_project: project) }
-
-        context "when MR has no rule" do
-          it 'is valid as project rule will be active' do
-            expect(merge_request).to be_valid
-          end
-        end
-
-        context "when MR rules exists but do not reference all project rules" do
-          it 'is invalid' do
-            merge_request.approval_rules.build(name: 'mr1', approval_project_rule_id: project_rule1.id)
-
-            expect(merge_request).to be_invalid
-            expect(merge_request.errors.added?(:approval_rules, :invalid_sourcing_to_project_rules)).to eq(true)
-          end
-        end
-
-        context "when MR rules exists but reference rules other than the project's" do
-          let(:other_project_rule) { create(:approval_project_rule) }
-
-          it 'is invalid' do
-            merge_request.approval_rules.build(name: 'mr1', approval_project_rule_id: project_rule1.id)
-            merge_request.approval_rules.build(name: 'mr2', approval_project_rule_id: project_rule2.id)
-            merge_request.approval_rules.build(name: 'mr3', approval_project_rule_id: other_project_rule.id)
-
-            expect(merge_request).to be_invalid
-            expect(merge_request.errors.added?(:approval_rules, :invalid_sourcing_to_project_rules)).to eq(true)
-          end
-        end
-
-        context "when MR's rules exists and reference all project's rules" do
-          it 'is valid' do
-            merge_request.approval_rules.build(name: 'mr1', approval_project_rule_id: project_rule1.id)
-            merge_request.approval_rules.build(name: 'mr2', approval_project_rule_id: project_rule2.id)
-
-            expect(merge_request).to be_valid
-          end
-        end
-      end
-
-      context "when updating" do
-        subject!(:merge_request) do
-          merge_request = build(:merge_request, source_project: project, target_project: project)
-          merge_request.approval_rules.build(name: 'mr1', approval_project_rule_id: project_rule1.id)
-          merge_request.approval_rules.build(name: 'mr2', approval_project_rule_id: project_rule2.id)
-          merge_request.save!
-          merge_request
-        end
-
-        context "when MR rules reference rules other than the project's" do
-          let(:other_project_rule) { create(:approval_project_rule) }
-
-          it 'is invalid' do
-            merge_request.approval_rules.build(name: 'mr3', approval_project_rule_id: other_project_rule.id)
-
-            expect(merge_request).to be_invalid
-            expect(merge_request.errors.added?(:approval_rules, :invalid_sourcing_to_project_rules)).to eq(true)
-          end
-        end
-
-        context 'when project later added a new rule' do
-          before do
-            project.approval_rules.create(name: 'p3')
-          end
-
-          it 'can still be saved' do
-            subject.reload
-            subject.title = 'foobar'
-
-            expect(subject.save).to eq(true)
-          end
-        end
-      end
-    end
-  end
-
   describe '#participant_approvers' do
     let(:approvers) { create_list(:user, 2) }
     let(:code_owners) { create_list(:user, 2) }