fix: Adjust save button behaviour in identifier settings

app/components/work_packages/admin/settings/identifier_settings_form_component.html.erb

@@ -77,7 +77,7 @@
               scheme: :primary,
               type: :submit,
               form: form_id,
-              hidden: show_autofix_section?,
+              hidden: true,
               data: { admin__work_packages_identifier_target: "saveButton" }
             )
           ) { t("button_save") } %>

app/components/work_packages/admin/settings/identifier_settings_form_component.rb

@@ -101,7 +101,8 @@ module WorkPackages
           {
             data: {
               controller: "admin--work-packages-identifier",
-              admin__work_packages_identifier_has_problematic_projects_value: has_problematic_projects?
+              admin__work_packages_identifier_has_problematic_projects_value: has_problematic_projects?,
+              admin__work_packages_identifier_current_value_value: Setting[:work_packages_identifier]
             }
           }
         end

frontend/src/stimulus/controllers/dynamic/admin/work-packages-identifier.controller.ts

@@ -33,36 +33,49 @@ import { Controller } from '@hotwired/stimulus';
 export default class WorkPackagesIdentifierController extends Controller {
   static values = {
     hasProblematicProjects: Boolean,
+    currentValue: String,
   };
 
   static targets = ['autofixSection', 'saveButton', 'autofixButton'];
 
   declare readonly hasProblematicProjectsValue:boolean;
+  declare readonly currentValueValue:string;
 
   declare readonly autofixSectionTarget:HTMLElement;
   declare readonly saveButtonTarget:HTMLButtonElement;
   declare readonly autofixButtonTarget:HTMLButtonElement;
+  declare readonly hasSaveButtonTarget:boolean;
+
+  private readonly resetBeforeCache = ():void => {
+    if (this.hasSaveButtonTarget) this.saveButtonTarget.hidden = true;
+  };
 
   connect() {
+    document.addEventListener('turbo:before-cache', this.resetBeforeCache);
     this.updateVisibility();
   }
 
+  disconnect() {
+    document.removeEventListener('turbo:before-cache', this.resetBeforeCache);
+  }
+
   handleChange() {
     this.updateVisibility();
   }
 
   private updateVisibility() {
-    const showAutofix = this.isSemanticSelected() && this.hasProblematicProjectsValue;
+    const selectedValue = this.selectedValue();
+    const showAutofix   = selectedValue === 'semantic' && this.hasProblematicProjectsValue;
+    const isDirty       = selectedValue !== this.currentValueValue;
 
     this.autofixSectionTarget.hidden = !showAutofix;
-    this.saveButtonTarget.hidden     =  showAutofix;
+    this.saveButtonTarget.hidden     =  showAutofix || !isDirty;
     this.autofixButtonTarget.hidden  = !showAutofix;
   }
 
-  private isSemanticSelected():boolean {
-    const checked = this.element.querySelector<HTMLInputElement>(
+  private selectedValue():string | undefined {
+    return this.element.querySelector<HTMLInputElement>(
       'input[name="settings[work_packages_identifier]"]:checked',
-    );
-    return checked?.value === 'semantic';
+    )?.value;
   }
 }

spec/components/work_packages/admin/settings/identifier_settings_form_component_spec.rb

@@ -130,9 +130,9 @@ RSpec.describe WorkPackages::Admin::Settings::IdentifierSettingsFormComponent, t
       expect(ProjectIdentifiers::IdentifierAutofix::PreviewQuery).to have_received(:new).once
     end
 
-    it "renders the save button" do
+    it "renders the save button (hidden until a change is made)" do
       render_component(component)
-      expect(page).to have_button("Save")
+      expect(page).to have_button("Save", visible: :all)
     end
 
     it "does not render in-progress or success content" do

spec/features/admin/settings/work_packages_identifier_spec.rb

@@ -49,6 +49,7 @@ RSpec.describe "Work packages identifier admin settings", :js do
   context "when no projects have problematic identifiers" do
     it "saves the setting without showing a dialog" do
       visit_settings
+      choose "Project-based semantic identifiers"
 
       click_button "Save"
 
@@ -60,9 +61,10 @@ RSpec.describe "Work packages identifier admin settings", :js do
   context "when a project has a problematic identifier" do
     shared_let(:project) { create(:project, identifier: "bad-id", name: "Bad Project") }
 
-    context "when saving with the current classic setting" do
+    context "when switching from semantic to classic", with_settings: { work_packages_identifier: "semantic" } do
       it "saves without showing the confirmation dialog" do
         visit_settings
+        choose "Instance-wide numerical sequence (default)"
 
         # The autofix section is hidden when classic is selected
         expect(page).to have_css(

spec/services/project_identifiers/identifier_autofix/problematic_identifiers_spec.rb

@@ -160,7 +160,7 @@ RSpec.describe ProjectIdentifiers::IdentifierAutofix::ProblematicIdentifiers do
     end
   end
 
-  describe "#reserved_identifiers_by_error_reasons" do
+  describe "#reserved_identifiers_for_admin_preview" do
     subject(:exclusion) { analysis.reserved_identifiers_for_admin_preview }
 
     let!(:valid_project) { create_project_with_raw_identifier(name: "Alpha", identifier: "ALPHA") }