Directive that provides support for MatFormFieldControl (Angular Material) in NgSelect.

_ng-select-theme.scss

// WIP
@import '~@angular/material/theming';
@mixin ng-select-theme($theme) {
    $primary: map-get($theme, primary);
    $accent: map-get($theme, accent);
    $warn: map-get($theme, warn);
    $isdark: map-get($theme, is-dark);

    $foreground: map-get($theme, foreground);
    $background: map-get($theme, background);


    $highlight-color: if($isdark, mat-color($foreground, text)  ,mat-color($primary));

    .ng-select, .ng-select-container, .ng-input>input {
        color: mat-color($foreground, text) !important;
        font: inherit;
        font-family: inherit;
    }
    .ng-placeholder{
        display: none;
    }

    .ng-clear-wrapper, .ng-arrow-wrapper{
        height: 1em;
        color: mat-color($foreground, text, .4); 
    }
    .ng-clear-wrapper:hover, .ng-arrow-wrapper:hover{        
        color: mat-color($foreground, text); 
    }
    .ng-select .ng-arrow-wrapper .ng-arrow{
        border-left: 5px solid transparent;
        border-right: 5px solid transparent;
        border-top: 5px solid;
        height: 7px !important;
    }

    .ng-select.ng-select-single .ng-select-container .ng-value-container {
      height: 1em;
    }

    .ng-select.ng-select-multiple{
      .ng-value{
          // WIP
          color: mat-color($primary, default-contrast);
          background: mat-color($primary);
          padding: 2px 8px;
          border-radius: 12px;
          margin: 0 4px 2px 0;
          .ng-value-label{
            margin-left: 8px;
          }
      }
    }

    .ng-dropdown-panel{
        @include mat-elevation(4);
        background: mat-color($background, card);
        color: mat-color($foreground, text) !important;

        
        .mat-option.ng-option-selected:not(.ng-option-marked):not(:hover) {
          background: mat-color($background, card);
    
          &:not(.ng-option-disabled) {
            color: mat-color($foreground, text);
          }
        }
        
        // left: 0;
        &.ng-select-bottom {
            top: calc(100% + .9em );
        }
        &.ng-select-top {
            bottom: calc(100% + 1.25em);            
        }
        &.multiple {
            .ng-option {
                &.selected {
                    background: mat-color($background,card);
                }
                &.marked {
                    background: mat-color($foreground, text, .04);
                }
            }
        }
        
        .ng-dropdown-header {
            border-bottom: 1px solid mat-color($foreground, text,.12);
            padding: 0 16px;
            line-height: 3em;
            min-height: 3em;
        }

        .ng-dropdown-footer {
            border-top: 1px solid mat-color($foreground, text,.12);
            padding: 0 16px;
            line-height: 3em;
            min-height: 3em;
        }

        .ng-dropdown-panel-items {
            .ng-optgroup {
                user-select: none;
                cursor: pointer;
                line-height: 3em;
                height: 3em;
                padding: 0 16px;
                color: mat-color($foreground, text);
                font-weight: 500;
                &.ng-option-marked {
                    background:mat-color($foreground, text, .04);
                }
                &.ng-option-disabled {
                    cursor: default;
                }
                &.ng-option-selected {
                    background: mat-color($foreground, text, .12);
                    color: $highlight-color;
                }
            }
            .ng-option {
                line-height: 3em;
                min-height: 3em;
                white-space: nowrap;
                overflow: hidden;
                text-overflow: ellipsis;
                padding: 0 16px;
                text-decoration: none;
                position: relative;
                color: mat-color($foreground, text,.87);
                text-align: left;
         
                &.ng-option-marked {
                    background: mat-color($foreground, text, .04);
                    color: mat-color($foreground, text,.87);
                }
                &.ng-option-selected {
                    background: mat-color($foreground, text, .12);
                    color: $highlight-color;
                }
                &.ng-option-disabled {
                    color: mat-color($foreground, text, 0.38);
                }
                &.ng-option-child {
                    padding-left: 32px;                    
                }
                .ng-tag-label {
                    padding-right: 5px;
                    font-size: 80%;
                    font-weight: 400;
                    color: mat-color($foreground, text, 0.38);
                }
            }
        }
    }
}

example.html

<mat-form-field>
    <ng-select placeholder="Select" ngSelectMat [items]="simpleItems" [(ngModel)]="selectedSimpleItem" required="true" #model="ngModel"></ng-select>
    <mat-error *ngIf="model.invalid">Required</mat-error>
</mat-form-field>

ng-select.directive.ts

import { MatFormFieldControl } from '@angular/material/form-field';
import { Directive, HostBinding, Input, Optional, Self, OnDestroy, DoCheck } from '@angular/core';
import { Subject } from 'rxjs';
import { NgControl, FormControl, FormGroupDirective, NgForm } from '@angular/forms';
import { NgSelectComponent } from '@ng-select/ng-select';
import { coerceBooleanProperty } from '@angular/cdk/coercion';
import { untilDestroyed } from 'ngx-take-until-destroy';
import { ErrorStateMatcher } from '@angular/material/core';


export class NgSelectErrorStateMatcher {
  constructor(private ngSelect: NgSelectFormFieldControlDirective) {
  }
  isErrorState(control: FormControl | null, form: FormGroupDirective | NgForm | null): boolean {
    if (!control) {
      return this.ngSelect.required && this.ngSelect.empty;
    } else {
      return !!(control && control.invalid && (control.touched || (form && form.submitted)));
    }
  }
}

@Directive({
  // tslint:disable-next-line:directive-selector
  selector: '[ngSelectMat]',
  providers: [{ provide: MatFormFieldControl, useExisting: NgSelectFormFieldControlDirective }],
})
export class NgSelectFormFieldControlDirective implements MatFormFieldControl<any>, OnDestroy, DoCheck {
  static nextId = 0;
  @HostBinding() @Input() id = `ng-select-${NgSelectFormFieldControlDirective.nextId++}`;
  @HostBinding('attr.aria-describedby') describedBy = '';



  get empty(): boolean {
    return this._value === undefined || this._value === null;
  }
  errorState = false;
  @Input() errorStateMatcher: ErrorStateMatcher;
  private _defaultErrorStateMatcher: ErrorStateMatcher = new NgSelectErrorStateMatcher(this);
  // controlType?: string;
  // autofilled?: boolean;

  stateChanges = new Subject<void>();
  focused = false;

  get shouldLabelFloat() { return this.focused || !this.empty; }

  @Input()
  get placeholder(): string { return this._placeholder; }
  set placeholder(value: string) {
    this._placeholder = value;
    this.stateChanges.next();
  }
  private _placeholder: string;

  @Input()
  get required(): boolean { return this._required; }
  set required(value: boolean) {
    this._required = coerceBooleanProperty(value);
    this.stateChanges.next();
  }
  private _required = false;

  @Input()
  get disabled(): boolean { return this._disabled; }
  set disabled(value: boolean) {
    this._disabled = coerceBooleanProperty(value);
    this.stateChanges.next();
  }
  private _disabled = false;

  @Input()
  get value(): any {
    return this._value;
  }
  set value(v: any) {
    this._value = v;
    this.stateChanges.next();
  }
  private _value: any;

  constructor(
    private host: NgSelectComponent,
    @Optional() @Self() public ngControl: NgControl,
    @Optional() private _parentForm: NgForm,
    @Optional() private _parentFormGroup: FormGroupDirective,
  ) {
    host.focusEvent.asObservable().pipe(untilDestroyed(this)).subscribe(v => {
      this.focused = true;
      this.stateChanges.next();
    });
    host.blurEvent.asObservable().pipe(untilDestroyed(this)).subscribe(v => {
      this.focused = false;
      this.stateChanges.next();
    });


    if (this.ngControl) {
      this._value = this.ngControl.value;
      this._disabled = this.ngControl.disabled;
      this.ngControl.statusChanges.pipe(untilDestroyed(this)).subscribe(s => {
        const disabled = s === 'DISABLED';
        if (disabled !== this._disabled) {
          this.disabled = disabled;
        }
      });
      this.ngControl.valueChanges.pipe(untilDestroyed(this)).subscribe(v => {
         this._value = v;
         this.host.detectChanges();
        this.stateChanges.next();
      });      
    } else {
      host.changeEvent.asObservable().pipe(untilDestroyed(this)).subscribe(v => {
        this._value = v;
        this.host.detectChanges();
        this.stateChanges.next();
      });
    }
  }

  ngOnDestroy() { }

  ngDoCheck() {

    // We need to re-evaluate this on every change detection cycle, because there are some
    // error triggers that we can't subscribe to (e.g. parent form submissions). This means
    // that whatever logic is in here has to be super lean or we risk destroying the performance.
    this.updateErrorState();

  }

  updateErrorState() {
    const oldState = this.errorState;
    const parent = this._parentFormGroup || this._parentForm;
    const matcher = this.errorStateMatcher || this._defaultErrorStateMatcher;
    const control = this.ngControl ? this.ngControl.control as FormControl : null;
    const newState = matcher.isErrorState(control, parent);

    if (newState !== oldState) {
      this.errorState = newState;
      this.stateChanges.next();
    }
  }

  setDescribedByIds(ids: string[]): void {
    this.describedBy = ids.join(' ');
  }

  onContainerClick(event: MouseEvent): void {
    const target = event.target as HTMLElement;
    if (target.classList.contains('mat-form-field-infix')) {
      this.host.focus();
      this.host.open();
    }

  }

}

As I had issues with the approach above, I went to the source and did some minor modifications and got a usable result with minimal changes (all commented in the source). Now I'm able to use kendo angular controls with this directive inside mat-form-fields.

/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 *
 * Altered version of:
 * - https://github.com/angular/components/blob/master/src/material/input/input.ts
 *
 * Changes:
 * - new generic selector
 * - bypassed _validateType, removed type get/set
 * - value get/set altered to use the underlying ngControl value (search for nativeElement.value vs ngControl.value)
 * - set default values (angular 11 strict mode) for:
 *   - _id
 *   - placeholder
 *   - errorStateMatcher
 *   - userAriaDescribedBy
 * - altered (bypassed) _isNeverEmpty
 * - altered get empty()
 */

import { BooleanInput, coerceBooleanProperty } from '@angular/cdk/coercion';
import { getSupportedInputTypes, Platform } from '@angular/cdk/platform';
import { AutofillMonitor } from '@angular/cdk/text-field';
import {
  AfterViewInit,
  Directive,
  DoCheck,
  ElementRef,
  HostListener,
  Inject,
  Input,
  NgZone,
  OnChanges,
  OnDestroy,
  Optional,
  Self
} from '@angular/core';
import { FormGroupDirective, NgControl, NgForm, Validators } from '@angular/forms';
import { CanUpdateErrorState, ErrorStateMatcher, mixinErrorState } from '@angular/material/core';
import { MatFormField, MatFormFieldControl, MAT_FORM_FIELD } from '@angular/material/form-field';
import { MAT_INPUT_VALUE_ACCESSOR } from '@angular/material/input';
import { Subject } from 'rxjs';

let nextUniqueId = 0;

// Boilerplate for applying mixins to MatInput.
/** @docs-private */
const _MatInputBase = mixinErrorState(
  class {
    constructor(
      public _defaultErrorStateMatcher: ErrorStateMatcher,
      public _parentForm: NgForm,
      public _parentFormGroup: FormGroupDirective,
      /** @docs-private */
      public ngControl: NgControl,
    ) { }
  },
);

/** Directive that allows a native input to work inside a `MatFormField`. */
@Directive({
  selector: `[matInputEx]`,
  exportAs: 'matInputEx',
  host: {
    /**
     * @breaking-change 8.0.0 remove .mat-form-field-autofill-control in favor of AutofillMonitor.
     */
    'class': 'mat-input-element mat-form-field-autofill-control',
    '[class.mat-input-server]': '_isServer',
    // Native input properties that are overwritten by Angular inputs need to be synced with
    // the native input element. Otherwise property bindings for those don't work.
    '[attr.id]': 'id',
    // At the time of writing, we have a lot of customer tests that look up the input based on its
    // placeholder. Since we sometimes omit the placeholder attribute from the DOM to prevent screen
    // readers from reading it twice, we have to keep it somewhere in the DOM for the lookup.
    '[attr.data-placeholder]': 'placeholder',
    '[disabled]': 'disabled',
    '[required]': 'required',
    '[attr.readonly]': 'readonly && !_isNativeSelect || null',
    '[class.mat-native-select-inline]': '_isInlineSelect()',
    // Only mark the input as invalid for assistive technology if it has a value since the
    // state usually overlaps with `aria-required` when the input is empty and can be redundant.
    '[attr.aria-invalid]': '(empty && required) ? null : errorState',
    '[attr.aria-required]': 'required',
  },
  providers: [{ provide: MatFormFieldControl, useExisting: MatInputEx }],
})
export class MatInputEx
  extends _MatInputBase
  implements
  MatFormFieldControl<any>,
  OnChanges,
  OnDestroy,
  AfterViewInit,
  DoCheck,
  CanUpdateErrorState {
  protected _uid = `mat-input-${nextUniqueId++}`;
  protected _previousNativeValue: any;
  private _inputValueAccessor: { value: any };
  private _previousPlaceholder: string | null = null;

  /** Whether the component is being rendered on the server. */
  readonly _isServer: boolean;

  /** Whether the component is a native html select. */
  readonly _isNativeSelect: boolean;

  /** Whether the component is a textarea. */
  readonly _isTextarea: boolean;

  /** Whether the input is inside of a form field. */
  readonly _isInFormField: boolean;

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  focused: boolean = false;

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  override readonly stateChanges: Subject<void> = new Subject<void>();

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  controlType: string = 'mat-input';

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  autofilled = false;

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  @Input()
  get disabled(): boolean {
    if (this.ngControl && this.ngControl.disabled !== null) {
      return this.ngControl.disabled;
    }
    return this._disabled;
  }
  set disabled(value: boolean) {
    this._disabled = coerceBooleanProperty(value);

    // Browsers may not fire the blur event if the input is disabled too quickly.
    // Reset from here to ensure that the element doesn't become stuck.
    if (this.focused) {
      this.focused = false;
      this.stateChanges.next();
    }
  }
  protected _disabled = false;

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  @Input()
  get id(): string {
    return this._id;
  }
  set id(value: string) {
    this._id = value || this._uid;
  }
  protected _id: string = '';

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  @Input() placeholder: string = '';

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  @Input()
  get required(): boolean {
    return this._required ?? this.ngControl?.control?.hasValidator(Validators.required) ?? false;
  }
  set required(value: boolean) {
    this._required = coerceBooleanProperty(value);
  }
  protected _required: boolean | undefined;

  /** Input type of the element. */
  /*
  @Input()
  get type(): string {
    return this._type;
  }
  set type(value: string) {
    this._type = value || 'text';
    this._validateType();

    // When using Angular inputs, developers are no longer able to set the properties on the native
    // input element. To ensure that bindings for `type` work, we need to sync the setter
    // with the native property. Textarea elements don't support the type property or attribute.
    if (!this._isTextarea && getSupportedInputTypes().has(this._type)) {
      (this._elementRef.nativeElement as HTMLInputElement).type = this._type;
    }
  }
  protected _type = 'text';
  */

  /** An object used to control when error messages are shown. */
  @Input() override errorStateMatcher: ErrorStateMatcher = new ErrorStateMatcher();

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  @Input('aria-describedby') userAriaDescribedBy: string = '';

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  @Input()
  get value(): string {
    return this._inputValueAccessor.value;
  }
  set value(value: string) {
    if (value !== this.value) {
      this._inputValueAccessor.value = value;
      this.stateChanges.next();
    }
  }

  /** Whether the element is readonly. */
  @Input()
  get readonly(): boolean {
    return this._readonly;
  }
  set readonly(value: boolean) {
    this._readonly = coerceBooleanProperty(value);
  }
  private _readonly = false;

  protected _neverEmptyInputTypes = [
    'date',
    'datetime',
    'datetime-local',
    'month',
    'time',
    'week',
  ].filter(t => getSupportedInputTypes().has(t));

  constructor(
    protected _elementRef: ElementRef<HTMLInputElement | HTMLSelectElement | HTMLTextAreaElement>,
    protected _platform: Platform,
    @Optional() @Self() ngControl: NgControl,
    @Optional() _parentForm: NgForm,
    @Optional() _parentFormGroup: FormGroupDirective,
    _defaultErrorStateMatcher: ErrorStateMatcher,
    @Optional() @Self() @Inject(MAT_INPUT_VALUE_ACCESSOR) inputValueAccessor: any,
    private _autofillMonitor: AutofillMonitor,
    ngZone: NgZone,
    // TODO: Remove this once the legacy appearance has been removed. We only need
    // to inject the form-field for determining whether the placeholder has been promoted.
    @Optional() @Inject(MAT_FORM_FIELD) private _formField?: MatFormField,
  ) {
    super(_defaultErrorStateMatcher, _parentForm, _parentFormGroup, ngControl);

    const element = this._elementRef.nativeElement;
    const nodeName = element.nodeName.toLowerCase();

    // If no input value accessor was explicitly specified, use the element as the input value
    // accessor.
    this._inputValueAccessor = inputValueAccessor || element;

    this._previousNativeValue = this.value;

    // Force setter to be called in case id was not specified.
    this.id = this.id;

    // On some versions of iOS the caret gets stuck in the wrong place when holding down the delete
    // key. In order to get around this we need to "jiggle" the caret loose. Since this bug only
    // exists on iOS, we only bother to install the listener on iOS.
    if (_platform.IOS) {
      ngZone.runOutsideAngular(() => {
        _elementRef.nativeElement.addEventListener('keyup', (event: Event) => {
          const el = event.target as HTMLInputElement;

          // Note: We specifically check for 0, rather than `!el.selectionStart`, because the two
          // indicate different things. If the value is 0, it means that the caret is at the start
          // of the input, whereas a value of `null` means that the input doesn't support
          // manipulating the selection range. Inputs that don't support setting the selection range
          // will throw an error so we want to avoid calling `setSelectionRange` on them. See:
          // https://html.spec.whatwg.org/multipage/input.html#do-not-apply
          if (!el.value && el.selectionStart === 0 && el.selectionEnd === 0) {
            // Note: Just setting `0, 0` doesn't fix the issue. Setting
            // `1, 1` fixes it for the first time that you type text and
            // then hold delete. Toggling to `1, 1` and then back to
            // `0, 0` seems to completely fix it.
            el.setSelectionRange(1, 1);
            el.setSelectionRange(0, 0);
          }
        });
      });
    }

    this._isServer = !this._platform.isBrowser;
    this._isNativeSelect = nodeName === 'select';
    this._isTextarea = nodeName === 'textarea';
    this._isInFormField = !!_formField;

    if (this._isNativeSelect) {
      this.controlType = (element as HTMLSelectElement).multiple
        ? 'mat-native-select-multiple'
        : 'mat-native-select';
    }
  }

  ngAfterViewInit() {
    if (this._platform.isBrowser) {
      this._autofillMonitor.monitor(this._elementRef.nativeElement).subscribe(event => {
        this.autofilled = event.isAutofilled;
        this.stateChanges.next();
      });
    }
  }

  ngOnChanges() {
    this.stateChanges.next();
  }

  ngOnDestroy() {
    this.stateChanges.complete();

    if (this._platform.isBrowser) {
      this._autofillMonitor.stopMonitoring(this._elementRef.nativeElement);
    }
  }

  ngDoCheck() {
    if (this.ngControl) {
      // We need to re-evaluate this on every change detection cycle, because there are some
      // error triggers that we can't subscribe to (e.g. parent form submissions). This means
      // that whatever logic is in here has to be super lean or we risk destroying the performance.
      this.updateErrorState();
    }

    // We need to dirty-check the native element's value, because there are some cases where
    // we won't be notified when it changes (e.g. the consumer isn't using forms or they're
    // updating the value using `emitEvent: false`).
    this._dirtyCheckNativeValue();

    // We need to dirty-check and set the placeholder attribute ourselves, because whether it's
    // present or not depends on a query which is prone to "changed after checked" errors.
    this._dirtyCheckPlaceholder();
  }

  /** Focuses the input. */
  focus(options?: FocusOptions): void {
    this._elementRef.nativeElement.focus(options);
  }

  // We have to use a `HostListener` here in order to support both Ivy and ViewEngine.
  // In Ivy the `host` bindings will be merged when this class is extended, whereas in
  // ViewEngine they're overwritten.
  // TODO(crisbeto): we move this back into `host` once Ivy is turned on by default.
  /** Callback for the cases where the focused state of the input changes. */
  // tslint:disable:no-host-decorator-in-concrete
  @HostListener('focus', ['true'])
  @HostListener('blur', ['false'])
  // tslint:enable:no-host-decorator-in-concrete
  _focusChanged(isFocused: boolean) {
    if (isFocused !== this.focused) {
      this.focused = isFocused;
      this.stateChanges.next();
    }
  }

  // We have to use a `HostListener` here in order to support both Ivy and ViewEngine.
  // In Ivy the `host` bindings will be merged when this class is extended, whereas in
  // ViewEngine they're overwritten.
  // TODO(crisbeto): we move this back into `host` once Ivy is turned on by default.
  // tslint:disable-next-line:no-host-decorator-in-concrete
  @HostListener('input')
  _onInput() {
    // This is a noop function and is used to let Angular know whenever the value changes.
    // Angular will run a new change detection each time the `input` event has been dispatched.
    // It's necessary that Angular recognizes the value change, because when floatingLabel
    // is set to false and Angular forms aren't used, the placeholder won't recognize the
    // value changes and will not disappear.
    // Listening to the input event wouldn't be necessary when the input is using the
    // FormsModule or ReactiveFormsModule, because Angular forms also listens to input events.
  }

  /** Does some manual dirty checking on the native input `placeholder` attribute. */
  private _dirtyCheckPlaceholder() {
    // If we're hiding the native placeholder, it should also be cleared from the DOM, otherwise
    // screen readers will read it out twice: once from the label and once from the attribute.
    // TODO: can be removed once we get rid of the `legacy` style for the form field, because it's
    // the only one that supports promoting the placeholder to a label.
    const placeholder = this._formField?._hideControlPlaceholder?.() ? null : this.placeholder;
    if (placeholder !== this._previousPlaceholder) {
      const element = this._elementRef.nativeElement;
      this._previousPlaceholder = placeholder;
      placeholder
        ? element.setAttribute('placeholder', placeholder)
        : element.removeAttribute('placeholder');
    }
  }

  /** Does some manual dirty checking on the native input `value` property. */
  protected _dirtyCheckNativeValue() {

    // NOTE: we're interested in the 3rd party control's value, which differs from the native-el.
    // const newValue = this._elementRef.nativeElement.value;
    const newValue = this.ngControl.value;

    if (this._previousNativeValue !== newValue) {
      this._previousNativeValue = newValue;
      this.stateChanges.next();
    }
  }

  /** Make sure the input is a supported type. */
  protected _validateType() {
    /*
    if (
      MAT_INPUT_INVALID_TYPES.indexOf(this._type) > -1 &&
      (typeof ngDevMode === 'undefined' || ngDevMode)
    ) {
      throw getMatInputUnsupportedTypeError(this._type);
    }
    */
  }

  /** Checks whether the input type is one of the types that are never empty. */
  protected _isNeverEmpty() {
    return false;
    // NOTE: for 3rd party controls we don't know if it's neverEmpty!
    // return this._neverEmptyInputTypes.indexOf(this._type) > -1;
  }

  /** Checks whether the input is invalid based on the native validation. */
  protected _isBadInput() {
    // The `validity` property won't be present on platform-server.
    let validity = (this._elementRef.nativeElement as HTMLInputElement).validity;
    return validity && validity.badInput;
  }

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  get empty(): boolean {
    return (
      !this._isNeverEmpty() &&

      // NOTE: we need to check the controls value (which in case of complex 3rd party control component differs from the nativeElement)
      // !this._elementRef.nativeElement.value &&
      !this.ngControl.value &&

      !this._isBadInput() &&
      !this.autofilled
    );
  }

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  get shouldLabelFloat(): boolean {
    if (this._isNativeSelect) {
      // For a single-selection `<select>`, the label should float when the selected option has
      // a non-empty display value. For a `<select multiple>`, the label *always* floats to avoid
      // overlapping the label with the options.
      const selectElement = this._elementRef.nativeElement as HTMLSelectElement;
      const firstOption: HTMLOptionElement | undefined = selectElement.options[0];

      // On most browsers the `selectedIndex` will always be 0, however on IE and Edge it'll be
      // -1 if the `value` is set to something, that isn't in the list of options, at a later point.
      return (
        this.focused ||
        selectElement.multiple ||
        !this.empty ||
        !!(selectElement.selectedIndex > -1 && firstOption && firstOption.label)
      );
    } else {
      return this.focused || !this.empty;
    }
  }

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  setDescribedByIds(ids: string[]) {
    if (ids.length) {
      this._elementRef.nativeElement.setAttribute('aria-describedby', ids.join(' '));
    } else {
      this._elementRef.nativeElement.removeAttribute('aria-describedby');
    }
  }

  /**
   * Implemented as part of MatFormFieldControl.
   * @docs-private
   */
  onContainerClick() {
    // Do not re-focus the input element if the element is already focused. Otherwise it can happen
    // that someone clicks on a time input and the cursor resets to the "hours" field while the
    // "minutes" field was actually clicked. See: https://github.com/angular/components/issues/12849
    if (!this.focused) {
      this.focus();
    }
  }

  /** Whether the form control is a native select that is displayed inline. */
  _isInlineSelect(): boolean {
    const element = this._elementRef.nativeElement as HTMLSelectElement;
    return this._isNativeSelect && (element.multiple || element.size > 1);
  }

  static ngAcceptInputType_disabled: BooleanInput;
  static ngAcceptInputType_readonly: BooleanInput;
  static ngAcceptInputType_required: BooleanInput;

  // Accept `any` to avoid conflicts with other directives on `<input>` that may
  // accept different types.
  static ngAcceptInputType_value: any;
}