refactor(devtools): refactors property view drag-and-drop behavior (#60286)

The main goal of this change is to remove `categoryOrder` which effectively hard-codes the supported length of `panels`. Adding another item to `panels` is not rendered unless that is added to `categoryOrder`.

My solution to this is to make the set of categories a signal, with each category able to produce the data inside it. This allow `CdkDragDrop` to rearrange categories but then still produce the correct data in the template without needing a separate array to track order.

Also removed `hidden` and inlined it in the template, since the logic was the same for every panel.

`moveItemInArray` is unfortunately an in-place move, so I needed to manually clone the array to ensure `panels` observes an immutable update which works better with signals and change detection.

PR Close #60286

devtools/projects/ng-devtools/src/lib/devtools-tabs/directive-explorer/property-tab/property-view/property-view-body.component.html

@@ -22,17 +22,16 @@
         </mat-expansion-panel>
       </div>
     }
-    @for (index of categoryOrder; track $index) {
+    @for (panel of panels(); track $index) {
       <div class="mat-accordion-content" cdkDrag>
-        @let panel = panels()[index];
-        @if (!panel.hidden) {
+        @if (panel.controls().dataSource.data.length > 0) {
           <mat-expansion-panel [class]="panel.class" [expanded]="true">
             <mat-expansion-panel-header collapsedHeight="25px" expandedHeight="25px">
               <mat-panel-title>{{ panel.title }}</mat-panel-title>
             </mat-expansion-panel-header>
             <ng-property-view-tree
-              [dataSource]="panel.controls.dataSource"
-              [treeControl]="panel.controls.treeControl"
+              [dataSource]="panel.controls().dataSource"
+              [treeControl]="panel.controls().treeControl"
               (updateValue)="updateValue($event)"
               (inspect)="handleInspect($event)"
             />

devtools/projects/ng-devtools/src/lib/devtools-tabs/directive-explorer/property-tab/property-view/property-view-body.component.ts

@@ -7,7 +7,7 @@
  */
 
 import {CdkDragDrop, moveItemInArray, CdkDropList, CdkDrag} from '@angular/cdk/drag-drop';
-import {Component, computed, forwardRef, input, output} from '@angular/core';
+import {Component, computed, forwardRef, input, output, signal} from '@angular/core';
 import {DirectivePosition, SerializedInjectedService} from 'protocol';
 
 import {
@@ -44,37 +44,23 @@ export class PropertyViewBodyComponent {
 
   readonly inspect = output<{node: FlatNode; directivePosition: DirectivePosition}>();
 
-  categoryOrder = [0, 1, 2];
-
-  readonly panels = computed<
+  protected readonly panels = signal([
     {
-      title: string;
-      hidden: boolean;
-      controls: DirectiveTreeData;
-      class: string;
-    }[]
-  >(() => {
-    return [
-      {
-        title: 'Inputs',
-        hidden: this.directiveInputControls().dataSource.data.length === 0,
-        controls: this.directiveInputControls(),
-        class: 'cy-inputs',
-      },
-      {
-        title: 'Outputs',
-        hidden: this.directiveOutputControls().dataSource.data.length === 0,
-        controls: this.directiveOutputControls(),
-        class: 'cy-outputs',
-      },
-      {
-        title: 'Properties',
-        hidden: this.directiveStateControls().dataSource.data.length === 0,
-        controls: this.directiveStateControls(),
-        class: 'cy-properties',
-      },
-    ];
-  });
+      title: 'Inputs',
+      controls: () => this.directiveInputControls(),
+      class: 'cy-inputs',
+    },
+    {
+      title: 'Outputs',
+      controls: () => this.directiveOutputControls(),
+      class: 'cy-outputs',
+    },
+    {
+      title: 'Properties',
+      controls: () => this.directiveStateControls(),
+      class: 'cy-properties',
+    },
+  ]);
 
   readonly controlsLoaded = computed(() => {
     return (
@@ -89,7 +75,9 @@ export class PropertyViewBodyComponent {
   }
 
   drop(event: CdkDragDrop<any, any>): void {
-    moveItemInArray(this.categoryOrder, event.previousIndex, event.currentIndex);
+    const panels = this.panels();
+    moveItemInArray(panels, event.previousIndex, event.currentIndex);
+    this.panels.set(Array.from(panels)); // Clone array for immutable update.
   }
 
   handleInspect(node: FlatNode): void {