adjust contract to allow setting dates on manually scheduled parent wps

app/contracts/work_packages/base_contract.rb

@@ -84,7 +84,7 @@ module WorkPackages
 
     attribute :start_date,
               writeable: ->(*) {
-                model.leaf?
+                model.leaf? || model.schedule_manually?
               } do
       if start_before_soonest_start?
         message = I18n.t('activerecord.errors.models.work_package.attributes.start_date.violates_relationships',
@@ -96,7 +96,7 @@ module WorkPackages
 
     attribute :due_date,
               writeable: ->(*) {
-                model.leaf?
+                model.leaf? || model.schedule_manually?
               }
 
     validates :due_date,

spec/features/work_packages/scheduling/scheduling_mode_spec.rb

@@ -84,7 +84,7 @@ describe 'scheduling mode',
   let(:user) { FactoryBot.create :admin }
   let(:work_packages_page) { Pages::SplitWorkPackage.new(wp, project) }
 
-  let(:start_date) { work_packages_page.edit_field(:startDate) }
+  let(:combined_field) { work_packages_page.edit_field(:combinedDate) }
 
   before do
     login_as(user)
@@ -95,14 +95,14 @@ describe 'scheduling mode',
 
   it 'can toggle the scheduling mode through the date modal' do
     expect(wp.schedule_manually).to eq false
-    start_date.activate!
-    start_date.expect_active!
+    combined_field.activate!
+    combined_field.expect_active!
 
-    start_date.expect_scheduling_mode manually: false
-    start_date.toggle_scheduling_mode
-    start_date.expect_scheduling_mode manually: true
+    combined_field.expect_scheduling_mode manually: false
+    combined_field.toggle_scheduling_mode
+    combined_field.expect_scheduling_mode manually: true
 
-    start_date.save!
+    combined_field.save!
     work_packages_page.expect_and_dismiss_notification message: 'Successful update.'
 
     work_package.reload

spec/lib/api/v3/work_packages/schema/specific_work_package_schema_spec.rb

@@ -208,30 +208,74 @@ describe ::API::V3::WorkPackages::Schema::SpecificWorkPackageSchema do
     end
 
     context 'start date' do
-      it 'is not writable when the work package is a parent' do
-        allow(work_package).to receive(:leaf?).and_return(false)
-        expect(subject.writable?(:start_date)).to be false
+      context 'work package is parent' do
+        before do
+          allow(work_package)
+            .to receive(:leaf?)
+            .and_return(false)
+        end
+
+        context 'scheduled automatically' do
+          it 'is not writable' do
+            expect(subject.writable?(:start_date)).to be false
+          end
+        end
+
+        context 'scheduled manually' do
+          before do
+            work_package.schedule_manually = true
+          end
+
+          it 'is writable' do
+            expect(subject.writable?(:start_date)).to be true
+          end
+        end
       end
 
-      it 'is writable when the work package is a leaf' do
-        allow(work_package).to receive(:leaf?).and_return(true)
-        expect(subject.writable?(:start_date)).to be true
+      context 'work package is a leaf' do
+        it 'is writable' do
+          allow(work_package).to receive(:leaf?).and_return(true)
+          expect(subject.writable?(:start_date)).to be true
+        end
       end
     end
 
-    context 'finish date' do
-      it 'is not writable when the work package is a parent' do
-        allow(work_package).to receive(:leaf?).and_return(false)
-        expect(subject.writable?(:due_date)).to be false
+    context 'due date' do
+      context 'work package is parent' do
+        before do
+          allow(work_package)
+            .to receive(:leaf?)
+            .and_return(false)
+        end
+
+        context 'scheduled automatically' do
+          it 'is not writable' do
+            expect(subject.writable?(:due_date)).to be false
+          end
+        end
+
+        context 'scheduled manually' do
+          before do
+            work_package.schedule_manually = true
+          end
+
+          it 'is writable' do
+            expect(subject.writable?(:due_date)).to be true
+          end
+        end
       end
 
-      it 'is writable when the work package is a leaf' do
-        allow(work_package).to receive(:leaf?).and_return(true)
-        expect(subject.writable?(:due_date)).to be true
+      context 'work package is a leaf' do
+        it 'is writable' do
+          allow(work_package).to receive(:leaf?).and_return(true)
+          expect(subject.writable?(:due_date)).to be true
+        end
       end
     end
 
     context 'date' do
+      # As a date only exists on milestones, which can have no children
+      # we do not need to check for differences caused by scheduling modes.
       before do
         allow(work_package.type).to receive(:is_milestone?).and_return(true)
       end