From b5af15a3328833aadfb0eec5d5a41d507ac4e3c7 Mon Sep 17 00:00:00 2001
From: Leon Senft <leonsenft@users.noreply.github.com>
Date: Wed, 25 Mar 2026 13:35:02 -0700
Subject: [PATCH] test(forms): support directive composition with `FormField`

Support composing the `FormField` directive with custom controls:
---
 packages/forms/signals/test/web/focus.spec.ts |  34 ++
 .../forms/signals/test/web/form_field.spec.ts | 511 ++++++++++++++++++
 2 files changed, 545 insertions(+)

diff --git a/packages/forms/signals/test/web/focus.spec.ts b/packages/forms/signals/test/web/focus.spec.ts
index fb78b799b90..998b6b24558 100644
--- a/packages/forms/signals/test/web/focus.spec.ts
+++ b/packages/forms/signals/test/web/focus.spec.ts
@@ -73,6 +73,40 @@ describe('FieldState focus behavior', () => {
     expect(document.activeElement).toBe(customControl.querySelector('input'));
   });
 
+  it('should delegate focus behavior to a custom control composed with a FormField', async () => {
+    let focusCalled = false;
+
+    @Component({
+      selector: 'custom-control',
+      hostDirectives: [{directive: FormField, inputs: ['formField']}],
+      template: '<input #input />',
+    })
+    class CustomControl {
+      readonly value = model<string>();
+      readonly input = viewChild.required<ElementRef<HTMLInputElement>>('input');
+      focus() {
+        focusCalled = true;
+        this.input().nativeElement.focus();
+      }
+    }
+
+    @Component({
+      imports: [CustomControl],
+      template: `<custom-control [formField]="f" />`,
+    })
+    class TestCmp {
+      readonly f = form(signal(''));
+    }
+
+    const fixture = await act(() => TestBed.createComponent(TestCmp));
+    const customControl = fixture.nativeElement.firstChild as HTMLInputElement;
+
+    await act(() => fixture.componentInstance.f().focusBoundControl());
+    expect(focusCalled).toBeTrue();
+    expect(document.activeElement).not.toBe(customControl);
+    expect(document.activeElement).toBe(customControl.querySelector('input'));
+  });
+
   it('should directly focus a custom control that has no custom focus logic', async () => {
     @Component({
       selector: 'custom-control',
diff --git a/packages/forms/signals/test/web/form_field.spec.ts b/packages/forms/signals/test/web/form_field.spec.ts
index 7fbc9c1a4e2..59bb030e8e0 100644
--- a/packages/forms/signals/test/web/form_field.spec.ts
+++ b/packages/forms/signals/test/web/form_field.spec.ts
@@ -207,6 +207,33 @@ describe('field directive', () => {
         expect(comp.customControl().dirty()).toBe(true);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model.required<string>();
+          readonly dirty = input.required<boolean>();
+        }
+
+        @Component({
+          template: ` <custom-control [formField]="f" /> `,
+          imports: [CustomControl],
+        })
+        class TestCmp {
+          readonly data = signal('');
+          readonly f = form(this.data);
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const comp = act(() => TestBed.createComponent(TestCmp)).componentInstance;
+        expect(comp.customControl().dirty()).toBe(false);
+        act(() => comp.f().markAsDirty());
+        expect(comp.customControl().dirty()).toBe(true);
+      });
+
       it('should bind to directive input on native control', () => {
         @Directive({selector: '[testDir]'})
         class TestDir {
@@ -385,6 +412,35 @@ describe('field directive', () => {
         expect(component.customControl().disabled()).toBe(true);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<boolean> {
+          readonly value = model(false);
+          readonly disabled = input(false);
+        }
+
+        @Component({
+          template: ` <custom-control [formField]="f" /> `,
+          imports: [CustomControl],
+        })
+        class TestCmp {
+          readonly disabled = signal(false);
+          readonly f = form(signal(false), (p) => {
+            disabled(p, this.disabled);
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const comp = act(() => TestBed.createComponent(TestCmp)).componentInstance;
+        expect(comp.customControl().disabled()).toBe(false);
+        act(() => comp.disabled.set(true));
+        expect(comp.customControl().disabled()).toBe(true);
+      });
+
       it('should bind to custom control', () => {
         @Component({selector: 'custom-control', template: ``})
         class CustomControl implements FormValueControl<boolean> {
@@ -618,6 +674,37 @@ describe('field directive', () => {
         ]);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model.required<string>();
+          readonly disabledReasons =
+            input.required<readonly WithOptionalFieldTree<DisabledReason>[]>();
+        }
+
+        @Component({
+          template: ` <custom-control [formField]="f" /> `,
+          imports: [CustomControl],
+        })
+        class TestCmp {
+          readonly data = signal('');
+          readonly f = form(this.data, (p) => {
+            disabled(p, () => 'Currently unavailable');
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const comp = act(() => TestBed.createComponent(TestCmp)).componentInstance;
+
+        expect(comp.customControl().disabledReasons()).toEqual([
+          {message: 'Currently unavailable', fieldTree: comp.f},
+        ]);
+      });
+
       it('should bind to custom control', () => {
         @Component({
           selector: 'custom-control',
@@ -788,6 +875,36 @@ describe('field directive', () => {
         expect(comp.customControl().errors()).toEqual([]);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model.required<string>();
+          readonly errors = input.required<readonly WithOptionalFieldTree<ValidationError>[]>();
+        }
+
+        @Component({
+          template: ` <custom-control [formField]="f" /> `,
+          imports: [CustomControl],
+        })
+        class TestCmp {
+          readonly data = signal('');
+          readonly f = form(this.data, (p) => {
+            required(p);
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const comp = act(() => TestBed.createComponent(TestCmp)).componentInstance;
+        expect(comp.customControl().errors()).toEqual([requiredError({fieldTree: comp.f})]);
+
+        act(() => comp.f().value.set('valid'));
+        expect(comp.customControl().errors()).toEqual([]);
+      });
+
       it('should bind to custom control', () => {
         @Component({
           selector: 'custom-control',
@@ -949,6 +1066,39 @@ describe('field directive', () => {
         expect(component.customControl().hidden()).toBe(false);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model.required<string>();
+          readonly hidden = input.required<boolean>();
+        }
+
+        const visible = signal(false);
+
+        @Component({
+          imports: [CustomControl],
+          template: `<custom-control [formField]="field()" />`,
+        })
+        class TestCmp {
+          readonly f = form(signal(''), (p) => {
+            hidden(p, () => !visible());
+          });
+          readonly field = signal(this.f);
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const component = fixture.componentInstance;
+        expect(component.customControl().hidden()).toBe(true);
+
+        act(() => visible.set(true));
+        expect(component.customControl().hidden()).toBe(false);
+      });
+
       it('should bind to a custom control', () => {
         @Component({selector: 'custom-control', template: ``})
         class CustomControl implements FormValueControl<string> {
@@ -1145,6 +1295,35 @@ describe('field directive', () => {
         expect(comp.customControl().invalid()).toBe(false);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model.required<string>();
+          readonly invalid = input.required<boolean>();
+        }
+
+        @Component({
+          template: ` <custom-control [formField]="f" /> `,
+          imports: [CustomControl],
+        })
+        class TestCmp {
+          readonly data = signal('');
+          readonly f = form(this.data, (p) => {
+            required(p);
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const comp = act(() => TestBed.createComponent(TestCmp)).componentInstance;
+        expect(comp.customControl().invalid()).toBe(true);
+        act(() => comp.f().value.set('valid'));
+        expect(comp.customControl().invalid()).toBe(false);
+      });
+
       it('should bind to custom control', () => {
         @Component({
           selector: 'custom-control',
@@ -1324,6 +1503,38 @@ describe('field directive', () => {
         expect(fixture.nativeElement.innerText).toBe('ab');
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '{{ value() }}',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model('');
+          readonly name = input('');
+        }
+
+        @Component({
+          imports: [CustomControl],
+          template: `
+            @for (item of f; track item) {
+              <custom-control [formField]="item" />
+            }
+          `,
+        })
+        class TestCmp {
+          readonly f = form(signal(['a', 'b']), {name: 'root'});
+          readonly controls = viewChildren(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const component = fixture.componentInstance;
+        const control0 = component.controls()[0];
+        const control1 = component.controls()[1];
+        expect(control0.name()).toBe('root.0');
+        expect(control1.name()).toBe('root.1');
+      });
+
       it('should bind to custom control', () => {
         @Component({selector: 'custom-control', template: `{{ value() }}`})
         class CustomControl implements FormValueControl<string> {
@@ -1473,6 +1684,52 @@ describe('field directive', () => {
         expect(comp.customControl().pending()).toBe(false);
       });
 
+      it('should bind to a custom control when composed as a host directive', async () => {
+        const {promise, resolve} = promiseWithResolvers<ValidationError[]>();
+
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model.required<string>();
+          readonly pending = input.required<boolean>();
+        }
+
+        @Component({
+          template: ` <custom-control [formField]="f" /> `,
+          imports: [CustomControl],
+        })
+        class TestCmp {
+          readonly data = signal('test');
+          readonly f = form(this.data, (p) => {
+            validateAsync(p, {
+              params: () => [],
+              factory: (params) =>
+                resource({
+                  params,
+                  loader: () => promise,
+                }),
+              onSuccess: (results) => results,
+              onError: () => null,
+            });
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const comp = fixture.componentInstance;
+
+        expect(comp.customControl().pending()).toBe(true);
+
+        resolve([]);
+        await promise;
+        await fixture.whenStable();
+
+        expect(comp.customControl().pending()).toBe(false);
+      });
+
       it('should be reset when field changes on custom control', async () => {
         const {promise, resolve} = promiseWithResolvers<ValidationError[]>();
 
@@ -1656,6 +1913,37 @@ describe('field directive', () => {
         expect(component.child().readonly()).toBe(true);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model('');
+          readonly readonly = input(false);
+        }
+
+        @Component({
+          imports: [CustomControl],
+          template: `<custom-control [formField]="f" />`,
+        })
+        class TestCmp {
+          readonly readonly = signal(false);
+          readonly f = form(signal(''), (p) => {
+            readonly(p, this.readonly);
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const component = fixture.componentInstance;
+        expect(component.customControl().readonly()).toBe(false);
+
+        act(() => component.readonly.set(true));
+        expect(component.customControl().readonly()).toBe(true);
+      });
+
       it('should bind to custom control', () => {
         @Component({selector: 'custom-control', template: ``})
         class CustomControl implements FormValueControl<string> {
@@ -1877,6 +2165,37 @@ describe('field directive', () => {
         expect(component.customControl().required()).toBe(true);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model('');
+          readonly required = input(false);
+        }
+
+        @Component({
+          imports: [CustomControl],
+          template: `<custom-control [formField]="f" />`,
+        })
+        class TestCmp {
+          readonly required = signal(false);
+          readonly f = form(signal(''), (p) => {
+            required(p, {when: this.required});
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const component = fixture.componentInstance;
+        expect(component.customControl().required()).toBe(false);
+
+        act(() => component.required.set(true));
+        expect(component.customControl().required()).toBe(true);
+      });
+
       it('should bind to custom control', () => {
         @Component({selector: 'custom-control', template: ``})
         class CustomControl implements FormValueControl<string> {
@@ -2098,6 +2417,37 @@ describe('field directive', () => {
         expect(component.customControl().max()).toBe(5);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<number> {
+          readonly value = model(0);
+          readonly max = input<number>();
+        }
+
+        @Component({
+          imports: [CustomControl],
+          template: `<custom-control [formField]="f" />`,
+        })
+        class TestCmp {
+          readonly max = signal(10);
+          readonly f = form(signal(5), (p) => {
+            max(p, this.max);
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const component = fixture.componentInstance;
+        expect(component.customControl().max()).toBe(10);
+
+        act(() => component.max.set(5));
+        expect(component.customControl().max()).toBe(5);
+      });
+
       it('should bind to custom control', () => {
         @Component({selector: 'custom-control', template: ``})
         class CustomControl implements FormValueControl<number> {
@@ -2319,6 +2669,37 @@ describe('field directive', () => {
         expect(component.customControl().min()).toBe(5);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<number> {
+          readonly value = model(0);
+          readonly min = input<number>();
+        }
+
+        @Component({
+          imports: [CustomControl],
+          template: `<custom-control [formField]="f" />`,
+        })
+        class TestCmp {
+          readonly min = signal(10);
+          readonly f = form(signal(15), (p) => {
+            min(p, this.min);
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const component = fixture.componentInstance;
+        expect(component.customControl().min()).toBe(10);
+
+        act(() => component.min.set(5));
+        expect(component.customControl().min()).toBe(5);
+      });
+
       it('should bind to custom control', () => {
         @Component({selector: 'custom-control', template: ``})
         class CustomControl implements FormValueControl<number> {
@@ -2540,6 +2921,37 @@ describe('field directive', () => {
         expect(component.customControl().maxLength()).toBe(5);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model('');
+          readonly maxLength = input<number>();
+        }
+
+        @Component({
+          imports: [CustomControl],
+          template: `<custom-control [formField]="f" />`,
+        })
+        class TestCmp {
+          readonly maxLength = signal(10);
+          readonly f = form(signal(''), (p) => {
+            maxLength(p, this.maxLength);
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const component = fixture.componentInstance;
+        expect(component.customControl().maxLength()).toBe(10);
+
+        act(() => component.maxLength.set(5));
+        expect(component.customControl().maxLength()).toBe(5);
+      });
+
       it('should bind to custom control', () => {
         @Component({selector: 'custom-control', template: ``})
         class CustomControl implements FormValueControl<string> {
@@ -2777,6 +3189,37 @@ describe('field directive', () => {
         expect(component.customControl().minLength()).toBe(5);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model('');
+          readonly minLength = input<number>();
+        }
+
+        @Component({
+          imports: [CustomControl],
+          template: `<custom-control [formField]="f" />`,
+        })
+        class TestCmp {
+          readonly minLength = signal(10);
+          readonly f = form(signal(''), (p) => {
+            minLength(p, this.minLength);
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const component = fixture.componentInstance;
+        expect(component.customControl().minLength()).toBe(10);
+
+        act(() => component.minLength.set(5));
+        expect(component.customControl().minLength()).toBe(5);
+      });
+
       it('should bind to custom control', () => {
         @Component({selector: 'custom-control', template: ``})
         class CustomControl implements FormValueControl<string> {
@@ -2994,6 +3437,37 @@ describe('field directive', () => {
         expect(component.customControl().pattern()).toEqual([/def/]);
       });
 
+      it('should bind to a custom control when composed as a host directive', () => {
+        @Component({
+          selector: 'custom-control',
+          template: '',
+          hostDirectives: [{directive: FormField, inputs: ['formField']}],
+        })
+        class CustomControl implements FormValueControl<string> {
+          readonly value = model('');
+          readonly pattern = input<readonly RegExp[]>([]);
+        }
+
+        @Component({
+          imports: [CustomControl],
+          template: `<custom-control [formField]="f" />`,
+        })
+        class TestCmp {
+          readonly pattern = signal(/abc/);
+          readonly f = form(signal(''), (p) => {
+            pattern(p, this.pattern);
+          });
+          readonly customControl = viewChild.required(CustomControl);
+        }
+
+        const fixture = act(() => TestBed.createComponent(TestCmp));
+        const component = fixture.componentInstance;
+        expect(component.customControl().pattern()).toEqual([/abc/]);
+
+        act(() => component.pattern.set(/def/));
+        expect(component.customControl().pattern()).toEqual([/def/]);
+      });
+
       it('should bind to custom control', () => {
         @Component({selector: 'custom-control', template: ``})
         class CustomControl implements FormValueControl<string> {
@@ -3448,6 +3922,43 @@ describe('field directive', () => {
     expect(cmp.f().value()).toBe('typing');
   });
 
+  it('synchronizes with a custom value control when composed as a host directive', () => {
+    @Component({
+      selector: 'my-input',
+      template: '<input #i [value]="value()" (input)="value.set(i.value)" />',
+      hostDirectives: [{directive: FormField, inputs: ['formField']}],
+    })
+    class CustomInput implements FormValueControl<string> {
+      value = model('');
+    }
+
+    @Component({
+      imports: [CustomInput],
+      template: `<my-input [formField]="f" />`,
+    })
+    class TestCmp {
+      f = form<string>(signal('test'));
+    }
+
+    const fix = act(() => TestBed.createComponent(TestCmp));
+    const input = fix.nativeElement.firstChild.firstChild as HTMLInputElement;
+    const cmp = fix.componentInstance as TestCmp;
+
+    // Initial state
+    expect(input.value).toBe('test');
+
+    // Model -> View
+    act(() => cmp.f().value.set('testing'));
+    expect(input.value).toBe('testing');
+
+    // View -> Model
+    act(() => {
+      input.value = 'typing';
+      input.dispatchEvent(new Event('input'));
+    });
+    expect(cmp.f().value()).toBe('typing');
+  });
+
   it('synchronizes with a custom value control directive', () => {
     @Directive({
       selector: 'input[my-input]',