refactor(form-field): explicitly set static flag on all queries

Continuation of #15680.

Explicitly marks all ViewChild and ContentChild queries so that the timing is consistent for apps using Ivy or ViewEngine.

Author: crisbeto

src/lib/form-field/form-field.ts

@@ -235,14 +235,31 @@ export class MatFormField extends _MatFormFieldMixinBase
    * @deprecated
    * @breaking-change 8.0.0
    */
-  @ViewChild('underline') underlineRef: ElementRef;
-
-  @ViewChild('connectionContainer') _connectionContainerRef: ElementRef;
-  @ViewChild('inputContainer') _inputContainerRef: ElementRef;
-  @ViewChild('label') private _label: ElementRef;
-  @ContentChild(MatFormFieldControl) _control: MatFormFieldControl<any>;
-  @ContentChild(MatPlaceholder) _placeholderChild: MatPlaceholder;
-  @ContentChild(MatLabel) _labelChild: MatLabel;
+  @ViewChild('underline', {static: false}) underlineRef: ElementRef;
+
+  @ViewChild('connectionContainer', {static: true}) _connectionContainerRef: ElementRef;
+  @ViewChild('inputContainer', {static: false}) _inputContainerRef: ElementRef;
+  @ViewChild('label', {static: false}) private _label: ElementRef;
+
+  @ContentChild(MatFormFieldControl, {static: false}) _controlNonStatic: MatFormFieldControl<any>;
+  @ContentChild(MatFormFieldControl, {static: true}) _controlStatic: MatFormFieldControl<any>;
+  get _control() {
+    // TODO(crisbeto): we need this hacky workaround in order to support both Ivy
+    // and ViewEngine. We should clean this up once Ivy is the default renderer.
+    return this._explicitFormFieldControl || this._controlNonStatic || this._controlStatic;
+  }
+  set _control(value) {
+    this._explicitFormFieldControl = value;
+  }
+  private _explicitFormFieldControl: MatFormFieldControl<any>;
+
+  @ContentChild(MatLabel, {static: false}) _labelChildNonStatic: MatLabel;
+  @ContentChild(MatLabel, {static: true}) _labelChildStatic: MatLabel;
+  get _labelChild() {
+    return this._labelChildNonStatic || this._labelChildStatic;
+  }
+
+  @ContentChild(MatPlaceholder, {static: false}) _placeholderChild: MatPlaceholder;
   @ContentChildren(MatError) _errorChildren: QueryList<MatError>;
   @ContentChildren(MatHint) _hintChildren: QueryList<MatHint>;
   @ContentChildren(MatPrefix) _prefixChildren: QueryList<MatPrefix>;

src/lib/select/select.spec.ts

@@ -2441,6 +2441,17 @@ describe('MatSelect', () => {
     }));
   });
 
+  describe('with ngIf and mat-label', () => {
+    beforeEach(async(() => configureMatSelectTestingModule([SelectWithNgIfAndLabel])));
+
+    it('should not throw when using ngIf on a select with an associated label', fakeAsync(() => {
+      expect(() => {
+        const fixture = TestBed.createComponent(SelectWithNgIfAndLabel);
+        fixture.detectChanges();
+      }).not.toThrow();
+    }));
+  });
+
   describe('inside of a form group', () => {
     beforeEach(async(() => configureMatSelectTestingModule([SelectInsideFormGroup])));
 
@@ -4983,3 +4994,17 @@ class SelectWithoutOptionCentering {
 class SelectWithFormFieldLabel {
   placeholder: string;
 }
+
+@Component({
+  template: `
+    <mat-form-field appearance="fill">
+      <mat-label>Select something</mat-label>
+      <mat-select *ngIf="showSelect">
+        <mat-option value="1">One</mat-option>
+      </mat-select>
+    </mat-form-field>
+  `
+})
+class SelectWithNgIfAndLabel {
+  showSelect = true;
+}

tools/public_api_guard/lib/form-field.d.ts

@@ -18,12 +18,16 @@ export declare class MatFormField extends _MatFormFieldMixinBase implements Afte
     readonly _canLabelFloat: boolean;
     _connectionContainerRef: ElementRef;
     _control: MatFormFieldControl<any>;
+    _controlNonStatic: MatFormFieldControl<any>;
+    _controlStatic: MatFormFieldControl<any>;
     _elementRef: ElementRef;
     _errorChildren: QueryList<MatError>;
     _hintChildren: QueryList<MatHint>;
     _hintLabelId: string;
     _inputContainerRef: ElementRef;
-    _labelChild: MatLabel;
+    readonly _labelChild: MatLabel;
+    _labelChildNonStatic: MatLabel;
+    _labelChildStatic: MatLabel;
     _labelId: string;
     _placeholderChild: MatPlaceholder;
     _prefixChildren: QueryList<MatPrefix>;