feat(forms): formGroupName and formArrayName also accepts a number (#32607)

For consistency, `FormGroupName` and `FormaArrayName` also accepts a
number as input's type like `FormControlName`

Closes https://github.com/angular/angular/issues/32436

PR Close #32607

packages/forms/src/directives/abstract_form_group_directive.ts

@@ -82,7 +82,9 @@ export class AbstractFormGroupDirective extends ControlContainer implements OnIn
    * @description
    * The path to this group from the top-level directive.
    */
-  get path(): string[] { return controlPath(this.name, this._parent); }
+  get path(): string[] {
+    return controlPath(this.name == null ? this.name : this.name.toString(), this._parent);
+  }
 
   /**
    * @description

packages/forms/src/directives/control_container.ts

@@ -23,7 +23,7 @@ export abstract class ControlContainer extends AbstractControlDirective {
    * The name for the control
    */
   // TODO(issue/24571): remove '!'.
-  name !: string;
+  name !: string | number | null;
 
   /**
    * @description

packages/forms/src/directives/reactive_directives/form_group_name.ts

@@ -76,9 +76,13 @@ export class FormGroupName extends AbstractFormGroupDirective implements OnInit,
    * @description
    * Tracks the name of the `FormGroup` bound to the directive. The name corresponds
    * to a key in the parent `FormGroup` or `FormArray`.
+   * Accepts a name as a string or a number.
+   * The name in the form of a string is useful for individual forms,
+   * while the numerical form allows for form groups to be bound
+   * to indices when iterating over groups in a `FormArray`.
    */
   // TODO(issue/24571): remove '!'.
-  @Input('formGroupName') name !: string;
+  @Input('formGroupName') name !: string | number | null;
 
   constructor(
       @Optional() @Host() @SkipSelf() parent: ControlContainer,
@@ -142,9 +146,13 @@ export class FormArrayName extends ControlContainer implements OnInit, OnDestroy
    * @description
    * Tracks the name of the `FormArray` bound to the directive. The name corresponds
    * to a key in the parent `FormGroup` or `FormArray`.
+   * Accepts a name as a string or a number.
+   * The name in the form of a string is useful for individual forms,
+   * while the numerical form allows for form arrays to be bound
+   * to indices when iterating over arrays in a `FormArray`.
    */
   // TODO(issue/24571): remove '!'.
-  @Input('formArrayName') name !: string;
+  @Input('formArrayName') name !: string | number | null;
 
   constructor(
       @Optional() @Host() @SkipSelf() parent: ControlContainer,
@@ -196,7 +204,9 @@ export class FormArrayName extends ControlContainer implements OnInit, OnDestroy
    * Returns an array that represents the path from the top-level form to this control.
    * Each index is the string name of the control on that level.
    */
-  get path(): string[] { return controlPath(this.name, this._parent); }
+  get path(): string[] {
+    return controlPath(this.name == null ? this.name : this.name.toString(), this._parent);
+  }
 
   /**
    * @description

tools/public_api_guard/forms/forms.d.ts

@@ -128,7 +128,7 @@ export declare const COMPOSITION_BUFFER_MODE: InjectionToken<boolean>;
 
 export declare abstract class ControlContainer extends AbstractControlDirective {
     readonly formDirective: Form | null;
-    name: string;
+    name: string | number | null;
     readonly path: string[] | null;
 }
 
@@ -194,7 +194,7 @@ export declare class FormArrayName extends ControlContainer implements OnInit, O
     readonly asyncValidator: AsyncValidatorFn | null;
     readonly control: FormArray;
     readonly formDirective: FormGroupDirective | null;
-    name: string;
+    name: string | number | null;
     readonly path: string[];
     readonly validator: ValidatorFn | null;
     constructor(parent: ControlContainer, validators: any[], asyncValidators: any[]);
@@ -322,7 +322,7 @@ export declare class FormGroupDirective extends ControlContainer implements Form
 }
 
 export declare class FormGroupName extends AbstractFormGroupDirective implements OnInit, OnDestroy {
-    name: string;
+    name: string | number | null;
     constructor(parent: ControlContainer, validators: any[], asyncValidators: any[]);
 }