/reassign should only work when multiple assignees are available

Only if the issuable allows multiple assignees the `/reassign` command
should be enabled.

While at it, put all EE-specific Quick Action in a separate file.

Also, port back the original CE specs of QuickActionsServices and put
the differences in a separate EE-only file.

app/services/ee/quick_actions/interpret_service.rb

+module EE
+  module QuickActions
+    module InterpretService
+      include ::Gitlab::QuickActions::Dsl
+
+      desc 'Change assignee(s)'
+      explanation do
+        'Change assignee(s)'
+      end
+      params '@user1 @user2'
+      condition do
+        issuable.allows_multiple_assignees? &&
+          issuable.persisted? &&
+          current_user.can?(:"admin_#{issuable.to_ability_name}", project)
+      end
+      command :reassign do |unassign_param|
+        @updates[:assignee_ids] = extract_users(unassign_param).map(&:id)
+      end
+
+      desc 'Set weight'
+      explanation do |weight|
+        "Sets weight to #{weight}." if weight
+      end
+      params ::Issue::WEIGHT_RANGE.to_s.squeeze('.').tr('.', '-')
+      condition do
+        issuable.supports_weight? &&
+          current_user.can?(:"admin_#{issuable.to_ability_name}", issuable)
+      end
+      parse_params do |weight|
+        weight.to_i if ::Issue.weight_filter_options.include?(weight.to_i)
+      end
+      command :weight do |weight|
+        @updates[:weight] = weight if weight
+      end
+
+      desc 'Clear weight'
+      explanation 'Clears weight.'
+      condition do
+        issuable.persisted? &&
+          issuable.supports_weight? &&
+          issuable.weight? &&
+          current_user.can?(:"admin_#{issuable.to_ability_name}", issuable)
+      end
+      command :clear_weight do
+        @updates[:weight] = nil
+      end
+    end
+  end
+end

app/services/quick_actions/interpret_service.rb

 module QuickActions
   class InterpretService < BaseService
     include Gitlab::QuickActions::Dsl
+    prepend EE::QuickActions::InterpretService
     attr_reader :issuable
@@ -146,32 +147,6 @@ module QuickActions
         end
     end
-    desc do
-      "Change assignee#{'(s)' if issuable.allows_multiple_assignees?}"
-    end
-    explanation do |users|
-      users = issuable.allows_multiple_assignees? ? users : users.take(1)
-      "Change #{'assignee'.pluralize(users.size)} to #{users.map(&:to_reference).to_sentence}."
-    end
-    params do
-      issuable.allows_multiple_assignees? ? '@user1 @user2' : '@user'
-    end
-    condition do
-      issuable.persisted? &&
-        current_user.can?(:"admin_#{issuable.to_ability_name}", project)
-    end
-    parse_params do |assignee_param|
-      extract_users(assignee_param)
-    end
-    command :reassign do |users|
-      @updates[:assignee_ids] =
-        if issuable.allows_multiple_assignees?
-          users.map(&:id)
-        else
-          [users.last.id]
-        end
-    end
-
     desc 'Set milestone'
     explanation do |milestone|
       "Sets the milestone to #{milestone.to_reference}." if milestone
@@ -471,34 +446,6 @@ module QuickActions
       @updates[:target_branch] = branch_name if project.repository.branch_names.include?(branch_name)
     end
-    desc 'Set weight'
-    explanation do |weight|
-      "Sets weight to #{weight}." if weight
-    end
-    params Issue::WEIGHT_RANGE.to_s.squeeze('.').tr('.', '-')
-    condition do
-      issuable.supports_weight? &&
-        current_user.can?(:"admin_#{issuable.to_ability_name}", issuable)
-    end
-    parse_params do |weight|
-      weight.to_i if Issue.weight_filter_options.include?(weight.to_i)
-    end
-    command :weight do |weight|
-      @updates[:weight] = weight if weight
-    end
-
-    desc 'Clear weight'
-    explanation 'Clears weight.'
-    condition do
-      issuable.persisted? &&
-        issuable.supports_weight? &&
-        issuable.weight? &&
-        current_user.can?(:"admin_#{issuable.to_ability_name}", issuable)
-    end
-    command :clear_weight do
-      @updates[:weight] = nil
-    end
-
     desc 'Move issue from one column of the board to another'
     explanation do |target_list_name|
       label = find_label_references(target_list_name).first

spec/services/ee/quick_actions/interpret_service_spec.rb

+require 'spec_helper'
+
+describe QuickActions::InterpretService, services: true do # rubocop:disable RSpec/FilePath
+  let(:user) { create(:user) }
+  let(:developer) { create(:user) }
+  let(:developer2) { create(:user) }
+  let(:project) { create(:empty_project, :public) }
+  let(:issue) { create(:issue, project: project) }
+  let(:service) { described_class.new(project, developer) }
+
+  before do
+    stub_licensed_features(multiple_issue_assignees: true)
+
+    project.add_developer(developer)
+  end
+
+  describe '#execute' do
+    context 'assign command' do
+      let(:content) { "/assign @#{developer.username}" }
+
+      context 'Issue' do
+        it 'fetches assignees and populates them if content contains /assign' do
+          issue.assignees << user
+
+          _, updates = service.execute(content, issue)
+
+          expect(updates[:assignee_ids]).to match_array([developer.id, user.id])
+        end
+
+        context 'assign command with multiple assignees' do
+          let(:content) { "/assign @#{developer.username} @#{developer2.username}" }
+
+          before do
+            project.add_developer(developer2)
+          end
+
+          it 'fetches assignee and populates assignee_ids if content contains /assign' do
+            _, updates = service.execute(content, issue)
+
+            expect(updates[:assignee_ids]).to match_array([developer.id, developer2.id])
+          end
+        end
+      end
+    end
+
+    context 'unassign command' do
+      let(:content) { '/unassign' }
+
+      context 'Issue' do
+        it 'unassigns user if content contains /unassign @user' do
+          issue.update(assignee_ids: [developer.id, developer2.id])
+
+          _, updates = service.execute("/unassign @#{developer2.username}", issue)
+
+          expect(updates).to eq(assignee_ids: [developer.id])
+        end
+
+        it 'unassigns both users if content contains /unassign @user @user1' do
+          user = create(:user)
+
+          issue.update(assignee_ids: [developer.id, developer2.id, user.id])
+
+          _, updates = service.execute("/unassign @#{developer2.username} @#{developer.username}", issue)
+
+          expect(updates).to eq(assignee_ids: [user.id])
+        end
+
+        it 'unassigns all the users if content contains /unassign' do
+          issue.update(assignee_ids: [developer.id, developer2.id])
+
+          _, updates = service.execute('/unassign', issue)
+
+          expect(updates[:assignee_ids]).to be_empty
+        end
+      end
+    end
+
+    context 'reassign command' do
+      let(:content) { "/reassign @#{user.username}" }
+
+      context 'Merge Request' do
+        let(:merge_request) { create(:merge_request, source_project: project) }
+
+        it 'does not recognize /reassign @user' do
+          _, updates = service.execute(content, merge_request)
+
+          expect(updates).to be_empty
+        end
+      end
+
+      context 'Issue' do
+        let(:content) { "/reassign @#{user.username}" }
+
+        before do
+          issue.update(assignee_ids: [developer.id])
+        end
+
+        context 'unlicensed' do
+          before do
+            stub_licensed_features(multiple_issue_assignees: false)
+          end
+
+          it 'does not recognize /reassign @user' do
+            _, updates = service.execute(content, issue)
+
+            expect(updates).to be_empty
+          end
+        end
+
+        it 'reassigns user if content contains /reassign @user' do
+          _, updates = service.execute("/reassign @#{user.username}", issue)
+
+          expect(updates).to eq(assignee_ids: [user.id])
+        end
+      end
+    end
+  end
+end

spec/services/quick_actions/interpret_service_spec.rb

@@ -11,6 +11,8 @@ describe QuickActions::InterpretService, services: true do
   let(:note) { build(:note, commit_id: merge_request.diff_head_sha) }
   before do
+    stub_licensed_features(multiple_issue_assignees: false)
+
     project.team << [developer, :developer]
   end
@@ -399,13 +401,10 @@ describe QuickActions::InterpretService, services: true do
       let(:content) { "/assign @#{developer.username}" }
       context 'Issue' do
-        it 'fetches assignees and populates them if content contains /assign' do
-          user = create(:user)
-          issue.assignees << user
-
+        it 'fetches assignee and populates assignee_ids if content contains /assign' do
           _, updates = service.execute(content, issue)
-          expect(updates[:assignee_ids]).to match_array([developer.id, user.id])
+          expect(updates[:assignee_ids]).to match_array([developer.id])
         end
       end
@@ -429,7 +428,7 @@ describe QuickActions::InterpretService, services: true do
         it 'fetches assignee and populates assignee_ids if content contains /assign' do
           _, updates = service.execute(content, issue)
-          expect(updates[:assignee_ids]).to match_array([developer.id, developer2.id])
+          expect(updates[:assignee_ids]).to match_array([developer.id])
         end
       end
@@ -456,30 +455,11 @@ describe QuickActions::InterpretService, services: true do
       let(:content) { '/unassign' }
       context 'Issue' do
-        it 'unassigns user if content contains /unassign @user' do
-          issue.update(assignee_ids: [developer.id, developer2.id])
-
-          _, updates = service.execute("/unassign @#{developer2.username}", issue)
-
-          expect(updates).to eq(assignee_ids: [developer.id])
-        end
-
-        it 'unassigns both users if content contains /unassign @user @user1' do
-          user = create(:user)
-
-          issue.update(assignee_ids: [developer.id, developer2.id, user.id])
-
-          _, updates = service.execute("/unassign @#{developer2.username} @#{developer.username}", issue)
-
-          expect(updates).to eq(assignee_ids: [user.id])
-        end
-
-        it 'unassigns all the users if content contains /unassign' do
-          issue.update(assignee_ids: [developer.id, developer2.id])
-
-          _, updates = service.execute('/unassign', issue)
-          expect(updates[:assignee_ids]).to be_empty
+        it 'populates assignee_ids: [] if content contains /unassign' do
+          issue.update(assignee_ids: [developer.id])
+          _, updates = service.execute(content, issue)
+          expect(updates).to eq(assignee_ids: [])
         end
       end
@@ -493,22 +473,6 @@ describe QuickActions::InterpretService, services: true do
       end
     end
-    context 'reassign command' do
-      let(:content) { '/reassign' }
-
-      context 'Issue' do
-        it 'reassigns user if content contains /reassign @user' do
-          user = create(:user)
-
-          issue.update(assignee_ids: [developer.id])
-
-          _, updates = service.execute("/reassign @#{user.username}", issue)
-
-          expect(updates).to eq(assignee_ids: [user.id])
-        end
-      end
-    end
-
     it_behaves_like 'milestone command' do
       let(:content) { "/milestone %#{milestone.title}" }
       let(:issuable) { issue }
@@ -997,7 +961,7 @@ describe QuickActions::InterpretService, services: true do
       it 'includes current assignee reference' do
         _, explanations = service.explain(content, issue)
-        expect(explanations).to eq(["Removes assignee #{developer.to_reference}."])
+        expect(explanations).to eq(["Removes assignee @#{developer.username}."])
       end
     end