Cast predicate methods to boolean

These predicate alias methods have nil as a possible return value, which
can cause potential confusion if we attempt to use their actual return
value rather than testing for its boolean nature. This raises problems
specifically in APIs where we expose the return value as a string, for
instance.

ee/app/models/ee/project.rb

@@ -534,7 +534,10 @@ module EE
     def require_password_to_approve
       super && password_authentication_enabled_for_web?
     end
-    alias_method :require_password_to_approve?, :require_password_to_approve
+
+    def require_password_to_approve?
+      !!require_password_to_approve
+    end
 
     def find_path_lock(path, exact_match: false, downstream: false)
       path_lock_finder = strong_memoize(:path_lock_finder) do
@@ -723,7 +726,10 @@ module EE
         ::Gitlab::CurrentSettings.disable_overriding_approvers_per_merge_request? || super
       end
     end
-    alias_method :disable_overriding_approvers_per_merge_request?, :disable_overriding_approvers_per_merge_request
+
+    def disable_overriding_approvers_per_merge_request?
+      !!disable_overriding_approvers_per_merge_request
+    end
 
     def merge_requests_author_approval
       strong_memoize(:merge_requests_author_approval) do
@@ -733,7 +739,10 @@ module EE
         super
       end
     end
-    alias_method :merge_requests_author_approval?, :merge_requests_author_approval
+
+    def merge_requests_author_approval?
+      !!merge_requests_author_approval
+    end
 
     def merge_requests_disable_committers_approval
       strong_memoize(:merge_requests_disable_committers_approval) do
@@ -742,7 +751,10 @@ module EE
         ::Gitlab::CurrentSettings.prevent_merge_requests_committers_approval? || super
       end
     end
-    alias_method :merge_requests_disable_committers_approval?, :merge_requests_disable_committers_approval
+
+    def merge_requests_disable_committers_approval?
+      !!merge_requests_disable_committers_approval
+    end
 
     def license_compliance(pipeline = latest_pipeline_with_reports(::Ci::JobArtifact.license_scanning_reports))
       SCA::LicenseCompliance.new(self, pipeline)

ee/spec/models/project_spec.rb

@@ -677,6 +677,30 @@ RSpec.describe Project do
       end
     end
 
+    shared_examples 'a predicate wrapper method' do
+      where(:wrapped_method_return, :subject_return) do
+        true  | true
+        false | false
+        nil   | false
+      end
+
+      with_them do
+        it 'returns the expected boolean value' do
+          expect(project)
+            .to receive(wrapped_method)
+            .and_return(wrapped_method_return)
+
+          expect(project.send("#{wrapped_method}?")).to be(subject_return)
+        end
+      end
+    end
+
+    describe '#disable_overriding_approvers_per_merge_request?' do
+      it_behaves_like 'a predicate wrapper method' do
+        let(:wrapped_method) { :disable_overriding_approvers_per_merge_request }
+      end
+    end
+
     describe '#merge_requests_disable_committers_approval' do
       it_behaves_like 'setting modified by application setting' do
         let(:setting) { :merge_requests_disable_committers_approval }
@@ -684,6 +708,18 @@ RSpec.describe Project do
       end
     end
 
+    describe '#merge_requests_disable_committers_approval?' do
+      it_behaves_like 'a predicate wrapper method' do
+        let(:wrapped_method) { :merge_requests_disable_committers_approval }
+      end
+    end
+
+    describe '#require_password_to_approve?' do
+      it_behaves_like 'a predicate wrapper method' do
+        let(:wrapped_method) { :require_password_to_approve }
+      end
+    end
+
     describe '#merge_requests_author_approval' do
       let(:setting) { :merge_requests_author_approval }
       let(:application_setting) { :prevent_merge_requests_author_approval }
@@ -715,6 +751,12 @@ RSpec.describe Project do
         end
       end
     end
+
+    describe '#merge_requests_author_approval?' do
+      it_behaves_like 'a predicate wrapper method' do
+        let(:wrapped_method) { :merge_requests_author_approval }
+      end
+    end
   end
 
   describe '#has_active_hooks?' do