Public MR-level approval state API endpoint

This endpoint behaves the same way as the existing
private `/approval_settings` API endpoint.

The difference is that this endpoint responds with
`eligible_approvers` instead of `approvers`.

The private endpoint should be removed in
https://gitlab.com/gitlab-org/gitlab-ee/issues/13574 together
with the private project-level endpoints.

ee/lib/api/merge_request_approvals.rb

@@ -26,6 +26,12 @@ module API
 
         render_api_error!(errors, 400)
       end
+
+      def get_merge_request_approval_state(present_with:)
+        merge_request = find_merge_request_with_access(params[:merge_request_iid])
+
+        present merge_request.approval_state, with: present_with, current_user: current_user
+      end
     end
 
     params do
@@ -57,9 +63,14 @@ module API
           hidden: true
         }
         get 'approval_settings' do
-          merge_request = find_merge_request_with_access(params[:merge_request_iid])
+          get_merge_request_approval_state(present_with: ::EE::API::Entities::MergeRequestApprovalSettings)
+        end
 
-          present merge_request.approval_state, with: ::EE::API::Entities::MergeRequestApprovalSettings, current_user: current_user
+        desc 'Get approval state of merge request' do
+          success ::EE::API::Entities::MergeRequestApprovalState
+        end
+        get 'approval_state' do
+          get_merge_request_approval_state(present_with: ::EE::API::Entities::MergeRequestApprovalState)
         end
 
         desc 'Change approval-related configuration' do

ee/lib/ee/api/entities.rb

@@ -330,14 +330,6 @@ module EE
         expose :contains_hidden_groups?, as: :contains_hidden_groups
       end
 
-      # Being used in private project-level approvals API.
-      # This overrides the `eligible_approvers` to be exposed as `approvers`.
-      #
-      # To be removed in https://gitlab.com/gitlab-org/gitlab-ee/issues/13574.
-      class ApprovalSettingRule < ApprovalRule
-        expose :approvers, using: ::API::Entities::UserBasic, override: true
-      end
-
       class MergeRequestApprovalRule < ApprovalRule
         class SourceRule < Grape::Entity
           expose :approvals_required
@@ -346,34 +338,52 @@ module EE
         expose :source_rule, using: SourceRule
       end
 
-      # Being used in private MR-level approvals API.
-      # This overrides the `eligible_approvers` to be exposed as `approvers` and
-      # include additional properties.
-      #
-      # To be made public in https://gitlab.com/gitlab-org/gitlab-ee/issues/13712
-      # and the `approvers` override can be removed.
-      class MergeRequestApprovalSettingRule < MergeRequestApprovalRule
-        expose :approvers, using: ::API::Entities::UserBasic, override: true
+      class MergeRequestApprovalStateRule < MergeRequestApprovalRule
         expose :code_owner
         expose :approved_approvers, as: :approved_by, using: ::API::Entities::UserBasic
         expose :approved?, as: :approved
       end
 
-      # Decorates ApprovalState
-      class MergeRequestApprovalSettings < Grape::Entity
+      class MergeRequestApprovalState < Grape::Entity
         expose :approval_rules_overwritten do |approval_state|
           approval_state.approval_rules_overwritten?
         end
 
-        expose :wrapped_approval_rules, as: :rules, using: MergeRequestApprovalSettingRule
+        expose :wrapped_approval_rules, as: :rules, using: MergeRequestApprovalStateRule
+      end
+
+      # Being used in private project-level approvals API.
+      # This overrides the `eligible_approvers` to be exposed as `approvers`.
+      #
+      # To be removed in https://gitlab.com/gitlab-org/gitlab-ee/issues/13574.
+      class ApprovalSettingRule < ApprovalRule
+        expose :approvers, using: ::API::Entities::UserBasic, override: true
       end
 
-      # Decorates Project
+      # Being used in private project-level approvals API.
+      #
+      # To be removed in https://gitlab.com/gitlab-org/gitlab-ee/issues/13574.
       class ProjectApprovalSettings < Grape::Entity
         expose :visible_approval_rules, as: :rules, using: ApprovalSettingRule
         expose :min_fallback_approvals, as: :fallback_approvals_required
       end
 
+      # Being used in private MR-level approvals API.
+      # This overrides the `eligible_approvers` to be exposed as `approvers`.
+      #
+      # To be removed in https://gitlab.com/gitlab-org/gitlab-ee/issues/13574.
+      class MergeRequestApprovalSettingRule < MergeRequestApprovalStateRule
+        expose :approvers, using: ::API::Entities::UserBasic, override: true
+      end
+
+      # Being used in private MR-level approvals API.
+      # This overrides the `rules` to be exposed using MergeRequestApprovalSettingRule.
+      #
+      # To be removed in https://gitlab.com/gitlab-org/gitlab-ee/issues/13574.
+      class MergeRequestApprovalSettings < MergeRequestApprovalState
+        expose :wrapped_approval_rules, as: :rules, using: MergeRequestApprovalSettingRule, override: true
+      end
+
       # @deprecated
       class Approver < Grape::Entity
         expose :user, using: ::API::Entities::UserBasic

ee/spec/requests/api/merge_request_approvals_spec.rb

@@ -10,6 +10,47 @@ describe API::MergeRequestApprovals do
   set(:approver) { create :user }
   set(:group) { create :group }
 
+  shared_examples_for 'an API endpoint for getting merge request approval state' do
+    context 'when source rule is present' do
+      let(:source_rule) { create(:approval_project_rule, project: project, approvals_required: 1, name: 'zoo') }
+
+      before do
+        rule.create_approval_merge_request_rule_source!(approval_project_rule: source_rule)
+
+        get api(url, user)
+      end
+
+      it 'returns source rule details' do
+        expect(response).to have_gitlab_http_status(200)
+        expect(json_response['rules'].size).to eq(1)
+
+        rule_response = json_response['rules'].first
+
+        expect(rule_response['source_rule']['approvals_required']).to eq(source_rule.approvals_required)
+      end
+    end
+
+    context 'when user cannot view a group included in groups' do
+      let(:private_group) { create(:group, :private) }
+
+      before do
+        rule.groups << private_group
+
+        get api(url, user)
+      end
+
+      it 'excludes private groups' do
+        expect(response).to have_gitlab_http_status(200)
+        expect(json_response['rules'].size).to eq(1)
+
+        rule_response = json_response['rules'].first
+
+        expect(rule_response['id']).to eq(rule.id)
+        expect(rule_response['groups'].size).to eq(0)
+      end
+    end
+  end
+
   describe 'GET :id/merge_requests/:merge_request_iid/approvals' do
     let!(:rule) { create(:approval_merge_request_rule, merge_request: merge_request, approvals_required: 2, name: 'foo') }
 
@@ -96,14 +137,19 @@ describe API::MergeRequestApprovals do
   end
 
   describe 'GET :id/merge_requests/:merge_request_iid/approval_settings' do
-    let!(:rule) { create(:approval_merge_request_rule, merge_request: merge_request, approvals_required: 2, name: 'foo') }
+    let(:rule) { create(:approval_merge_request_rule, merge_request: merge_request, approvals_required: 2, name: 'foo') }
+    let(:url) { "/projects/#{project.id}/merge_requests/#{merge_request.iid}/approval_settings" }
 
-    it 'retrieves the approval rules details' do
+    before do
       project.add_developer(approver)
       merge_request.approvals.create(user: approver)
       rule.users << approver
+    end
 
-      get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/approval_settings", user)
+    it_behaves_like 'an API endpoint for getting merge request approval state'
+
+    it 'retrieves the approval rules details' do
+      get api(url, user)
 
       expect(response).to have_gitlab_http_status(200)
       expect(json_response['rules'].size).to eq(1)
@@ -116,35 +162,22 @@ describe API::MergeRequestApprovals do
       expect(rule_response['approved_by'][0]['username']).to eq(approver.username)
       expect(rule_response['source_rule']).to eq(nil)
     end
+  end
 
-    context 'when source rule is present' do
-      let!(:source_rule) { create(:approval_project_rule, project: project, approvals_required: 1, name: 'zoo') }
-      let!(:rule) { create(:approval_merge_request_rule, merge_request: merge_request, approvals_required: 2, name: 'foo') }
-
-      it 'returns source rule details' do
-        project.add_developer(approver)
-        merge_request.approvals.create(user: approver)
-        rule.users << approver
-        rule.create_approval_merge_request_rule_source!(approval_project_rule: source_rule)
-
-        get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/approval_settings", user)
-
-        expect(response).to have_gitlab_http_status(200)
-        expect(json_response['rules'].size).to eq(1)
-
-        rule_response = json_response['rules'].first
+  describe 'GET :id/merge_requests/:merge_request_iid/approval_state' do
+    let(:rule) { create(:approval_merge_request_rule, merge_request: merge_request, approvals_required: 2, name: 'foo') }
+    let(:url) { "/projects/#{project.id}/merge_requests/#{merge_request.iid}/approval_state" }
 
-        expect(rule_response['source_rule']['approvals_required']).to eq(source_rule.approvals_required)
-      end
+    before do
+      project.add_developer(approver)
+      merge_request.approvals.create(user: approver)
+      rule.users << approver
     end
 
-    it 'excludes private groups' do
-      private_group = create(:group, :private)
-
-      rule.users << approver
-      rule.groups << private_group
+    it_behaves_like 'an API endpoint for getting merge request approval state'
 
-      get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/approval_settings", user)
+    it 'retrieves the approval state details' do
+      get api(url, user)
 
       expect(response).to have_gitlab_http_status(200)
       expect(json_response['rules'].size).to eq(1)
@@ -152,7 +185,10 @@ describe API::MergeRequestApprovals do
       rule_response = json_response['rules'].first
 
       expect(rule_response['id']).to eq(rule.id)
-      expect(rule_response['groups'].size).to eq(0)
+      expect(rule_response['name']).to eq('foo')
+      expect(rule_response['eligible_approvers'][0]['username']).to eq(approver.username)
+      expect(rule_response['approved_by'][0]['username']).to eq(approver.username)
+      expect(rule_response['source_rule']).to eq(nil)
     end
   end