From f0e56f01a4fb833ccace1248b227e3627e0f1f0d Mon Sep 17 00:00:00 2001
From: swseverance <sam.severance@merrillcorp.com>
Date: Wed, 29 Jul 2020 10:23:45 -0400
Subject: [PATCH] feat(material/datepicker): add `getValidDateOrNull` method
 (#19915)

Several components have identical implementations of a `_getValidDateOrNull` method. This PR reduces code duplication by adding a `getValidDateOrNull` method to the `DateAdapter` class for the components to use instead.
---
 .../adapter/moment-date-adapter.spec.ts       |  6 ++++++
 src/material/core/datetime/date-adapter.ts    | 10 +++++++++
 .../core/datetime/native-date-adapter.spec.ts | 12 +++++++++++
 src/material/datepicker/calendar.ts           | 16 ++++----------
 .../datepicker/date-range-input-parts.ts      |  5 +++--
 src/material/datepicker/date-range-input.ts   | 12 ++---------
 src/material/datepicker/datepicker-base.ts    | 10 +--------
 .../datepicker/datepicker-input-base.ts       | 21 +++++++------------
 src/material/datepicker/datepicker-input.ts   |  4 ++--
 src/material/datepicker/month-view.ts         | 18 ++++++----------
 src/material/datepicker/multi-year-view.ts    | 18 ++++++----------
 src/material/datepicker/year-view.ts          | 18 ++++++----------
 tools/public_api_guard/material/core.d.ts     |  1 +
 13 files changed, 67 insertions(+), 84 deletions(-)

diff --git a/src/material-moment-adapter/adapter/moment-date-adapter.spec.ts b/src/material-moment-adapter/adapter/moment-date-adapter.spec.ts
index 41a97f3a6dde..7eef19ef1dc8 100644
--- a/src/material-moment-adapter/adapter/moment-date-adapter.spec.ts
+++ b/src/material-moment-adapter/adapter/moment-date-adapter.spec.ts
@@ -319,6 +319,12 @@ describe('MomentDateAdapter', () => {
     expect(adapter.isDateInstance(d)).toBe(false);
   });
 
+  it('should provide a method to return a valid date or null', () => {
+    let d = moment();
+    expect(adapter.getValidDateOrNull(d)).toBe(d);
+    expect(adapter.getValidDateOrNull(moment(NaN))).toBeNull();
+  });
+
   it('should create valid dates from valid ISO strings', () => {
     assertValidDate(adapter.deserialize('1985-04-12T23:20:50.52Z'), true);
     assertValidDate(adapter.deserialize('1996-12-19T16:39:57-08:00'), true);
diff --git a/src/material/core/datetime/date-adapter.ts b/src/material/core/datetime/date-adapter.ts
index 812de536d019..15337667476e 100644
--- a/src/material/core/datetime/date-adapter.ts
+++ b/src/material/core/datetime/date-adapter.ts
@@ -203,6 +203,16 @@ export abstract class DateAdapter<D> {
    */
   abstract invalid(): D;
 
+ /**
+  * Given a potential date object, returns that same date object if it is
+  * a valid date, or `null` if it's not a valid date.
+  * @param obj The object to check.
+  * @returns A date or `null`.
+  */
+  getValidDateOrNull(obj: unknown): D | null {
+    return this.isDateInstance(obj) && this.isValid(obj as D) ? obj as D : null;
+  }
+
   /**
    * Attempts to deserialize a value to a valid date object. This is different from parsing in that
    * deserialize should only accept non-ambiguous, locale-independent formats (e.g. a ISO 8601
diff --git a/src/material/core/datetime/native-date-adapter.spec.ts b/src/material/core/datetime/native-date-adapter.spec.ts
index 7a165a8edf24..9411d9abe721 100644
--- a/src/material/core/datetime/native-date-adapter.spec.ts
+++ b/src/material/core/datetime/native-date-adapter.spec.ts
@@ -349,6 +349,18 @@ describe('NativeDateAdapter', () => {
     expect(adapter.isDateInstance(d)).toBe(false);
   });
 
+  it('should provide a method to return a valid date or null', () => {
+    let d = new Date();
+    expect(adapter.getValidDateOrNull(d)).toBe(d);
+    expect(adapter.getValidDateOrNull(new Date(NaN))).toBeNull();
+    expect(adapter.getValidDateOrNull(null)).toBeNull();
+    expect(adapter.getValidDateOrNull(undefined)).toBeNull();
+    expect(adapter.getValidDateOrNull('')).toBeNull();
+    expect(adapter.getValidDateOrNull(0)).toBeNull();
+    expect(adapter.getValidDateOrNull('Wed Jul 28 1993')).toBeNull();
+    expect(adapter.getValidDateOrNull('1595204418000')).toBeNull();
+  });
+
   it('should create dates from valid ISO strings', () => {
     assertValidDate(adapter.deserialize('1985-04-12T23:20:50.52Z'), true);
     assertValidDate(adapter.deserialize('1996-12-19T16:39:57-08:00'), true);
diff --git a/src/material/datepicker/calendar.ts b/src/material/datepicker/calendar.ts
index dcc37f147f51..7bf85a1a70c5 100644
--- a/src/material/datepicker/calendar.ts
+++ b/src/material/datepicker/calendar.ts
@@ -206,7 +206,7 @@ export class MatCalendar<D> implements AfterContentInit, AfterViewChecked, OnDes
   @Input()
   get startAt(): D | null { return this._startAt; }
   set startAt(value: D | null) {
-    this._startAt = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._startAt = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _startAt: D | null;
 
@@ -220,7 +220,7 @@ export class MatCalendar<D> implements AfterContentInit, AfterViewChecked, OnDes
     if (value instanceof DateRange) {
       this._selected = value;
     } else {
-      this._selected = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+      this._selected = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
     }
   }
   private _selected: DateRange<D> | D | null;
@@ -229,7 +229,7 @@ export class MatCalendar<D> implements AfterContentInit, AfterViewChecked, OnDes
   @Input()
   get minDate(): D | null { return this._minDate; }
   set minDate(value: D | null) {
-    this._minDate = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._minDate = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _minDate: D | null;
 
@@ -237,7 +237,7 @@ export class MatCalendar<D> implements AfterContentInit, AfterViewChecked, OnDes
   @Input()
   get maxDate(): D | null { return this._maxDate; }
   set maxDate(value: D | null) {
-    this._maxDate = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._maxDate = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _maxDate: D | null;
 
@@ -417,14 +417,6 @@ export class MatCalendar<D> implements AfterContentInit, AfterViewChecked, OnDes
     this.currentView = view;
   }
 
-  /**
-   * @param obj The object to check.
-   * @returns The given object if it is both a date instance and valid, otherwise null.
-   */
-  private _getValidDateOrNull(obj: any): D | null {
-    return (this._dateAdapter.isDateInstance(obj) && this._dateAdapter.isValid(obj)) ? obj : null;
-  }
-
   /** Returns the component instance that corresponds to the current calendar view. */
   private _getCurrentViewComponent() {
     return this.monthView || this.yearView || this.multiYearView;
diff --git a/src/material/datepicker/date-range-input-parts.ts b/src/material/datepicker/date-range-input-parts.ts
index 74c93d7f9303..f21954106485 100644
--- a/src/material/datepicker/date-range-input-parts.ts
+++ b/src/material/datepicker/date-range-input-parts.ts
@@ -200,7 +200,8 @@ const _MatDateRangeInputBase:
 export class MatStartDate<D> extends _MatDateRangeInputBase<D> implements CanUpdateErrorState {
   /** Validator that checks that the start date isn't after the end date. */
   private _startValidator: ValidatorFn = (control: AbstractControl): ValidationErrors | null => {
-    const start = this._getValidDateOrNull(this._dateAdapter.deserialize(control.value));
+    const start = this._dateAdapter.getValidDateOrNull(
+      this._dateAdapter.deserialize(control.value));
     const end = this._model ? this._model.selection.end : null;
     return (!start || !end ||
         this._dateAdapter.compareDate(start, end) <= 0) ?
@@ -284,7 +285,7 @@ export class MatStartDate<D> extends _MatDateRangeInputBase<D> implements CanUpd
 export class MatEndDate<D> extends _MatDateRangeInputBase<D> implements CanUpdateErrorState {
   /** Validator that checks that the end date isn't before the start date. */
   private _endValidator: ValidatorFn = (control: AbstractControl): ValidationErrors | null => {
-    const end = this._getValidDateOrNull(this._dateAdapter.deserialize(control.value));
+    const end = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(control.value));
     const start = this._model ? this._model.selection.start : null;
     return (!end || !start ||
         this._dateAdapter.compareDate(end, start) >= 0) ?
diff --git a/src/material/datepicker/date-range-input.ts b/src/material/datepicker/date-range-input.ts
index 10940b41f9fe..856f15318e70 100644
--- a/src/material/datepicker/date-range-input.ts
+++ b/src/material/datepicker/date-range-input.ts
@@ -129,7 +129,7 @@ export class MatDateRangeInput<D> implements MatFormFieldControl<DateRange<D>>,
   @Input()
   get min(): D | null { return this._min; }
   set min(value: D | null) {
-    this._min = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._min = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
     this._revalidate();
   }
   private _min: D | null;
@@ -138,7 +138,7 @@ export class MatDateRangeInput<D> implements MatFormFieldControl<DateRange<D>>,
   @Input()
   get max(): D | null { return this._max; }
   set max(value: D | null) {
-    this._max = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._max = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
     this._revalidate();
   }
   private _max: D | null;
@@ -319,14 +319,6 @@ export class MatDateRangeInput<D> implements MatFormFieldControl<DateRange<D>>,
     return formField && formField._hasFloatingLabel() ? formField._labelId : null;
   }
 
-  /**
-   * @param obj The object to check.
-   * @returns The given object if it is both a date instance and valid, otherwise null.
-   */
-  private _getValidDateOrNull(obj: any): D | null {
-    return (this._dateAdapter.isDateInstance(obj) && this._dateAdapter.isValid(obj)) ? obj : null;
-  }
-
   /** Re-runs the validators on the start/end inputs. */
   private _revalidate() {
     if (this._startInput) {
diff --git a/src/material/datepicker/datepicker-base.ts b/src/material/datepicker/datepicker-base.ts
index 40ffe697a959..72d62fd32c3d 100644
--- a/src/material/datepicker/datepicker-base.ts
+++ b/src/material/datepicker/datepicker-base.ts
@@ -253,7 +253,7 @@ export abstract class MatDatepickerBase<C extends MatDatepickerControl<D>, S,
     return this._startAt || (this._datepickerInput ? this._datepickerInput.getStartValue() : null);
   }
   set startAt(value: D | null) {
-    this._startAt = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._startAt = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _startAt: D | null;
 
@@ -641,14 +641,6 @@ export abstract class MatDatepickerBase<C extends MatDatepickerControl<D>, S,
     ]);
   }
 
-  /**
-   * @param obj The object to check.
-   * @returns The given object if it is both a date instance and valid, otherwise null.
-   */
-  private _getValidDateOrNull(obj: any): D | null {
-    return (this._dateAdapter.isDateInstance(obj) && this._dateAdapter.isValid(obj)) ? obj : null;
-  }
-
   static ngAcceptInputType_disabled: BooleanInput;
   static ngAcceptInputType_touchUi: BooleanInput;
 }
diff --git a/src/material/datepicker/datepicker-input-base.ts b/src/material/datepicker/datepicker-input-base.ts
index a6a67e3ce31b..0d5974de9043 100644
--- a/src/material/datepicker/datepicker-input-base.ts
+++ b/src/material/datepicker/datepicker-input-base.ts
@@ -77,7 +77,7 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
   set value(value: D | null) {
     value = this._dateAdapter.deserialize(value);
     this._lastValueValid = this._isValidValue(value);
-    value = this._getValidDateOrNull(value);
+    value = this._dateAdapter.getValidDateOrNull(value);
     const oldDate = this.value;
     this._assignValue(value);
     this._formatValue(value);
@@ -149,7 +149,8 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
 
   /** The form control validator for the date filter. */
   private _filterValidator: ValidatorFn = (control: AbstractControl): ValidationErrors | null => {
-    const controlValue = this._getValidDateOrNull(this._dateAdapter.deserialize(control.value));
+    const controlValue = this._dateAdapter.getValidDateOrNull(
+      this._dateAdapter.deserialize(control.value));
     const dateFilter = this._getDateFilter();
     return !dateFilter || !controlValue || dateFilter(controlValue) ?
         null : {'matDatepickerFilter': true};
@@ -157,7 +158,8 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
 
   /** The form control validator for the min date. */
   private _minValidator: ValidatorFn = (control: AbstractControl): ValidationErrors | null => {
-    const controlValue = this._getValidDateOrNull(this._dateAdapter.deserialize(control.value));
+    const controlValue = this._dateAdapter.getValidDateOrNull(
+      this._dateAdapter.deserialize(control.value));
     const min = this._getMinDate();
     return (!min || !controlValue ||
         this._dateAdapter.compareDate(min, controlValue) <= 0) ?
@@ -166,7 +168,8 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
 
   /** The form control validator for the max date. */
   private _maxValidator: ValidatorFn = (control: AbstractControl): ValidationErrors | null => {
-    const controlValue = this._getValidDateOrNull(this._dateAdapter.deserialize(control.value));
+    const controlValue = this._dateAdapter.getValidDateOrNull(
+      this._dateAdapter.deserialize(control.value));
     const max = this._getMaxDate();
     return (!max || !controlValue ||
         this._dateAdapter.compareDate(max, controlValue) >= 0) ?
@@ -318,7 +321,7 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
     const lastValueWasValid = this._lastValueValid;
     let date = this._dateAdapter.parse(value, this._dateFormats.parse.dateInput);
     this._lastValueValid = this._isValidValue(date);
-    date = this._getValidDateOrNull(date);
+    date = this._dateAdapter.getValidDateOrNull(date);
 
     if (!this._dateAdapter.sameDate(date, this.value)) {
       this._assignValue(date);
@@ -358,14 +361,6 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
         value ? this._dateAdapter.format(value, this._dateFormats.display.dateInput) : '';
   }
 
-  /**
-   * @param obj The object to check.
-   * @returns The given object if it is both a date instance and valid, otherwise null.
-   */
-  protected _getValidDateOrNull(obj: any): D | null {
-    return (this._dateAdapter.isDateInstance(obj) && this._dateAdapter.isValid(obj)) ? obj : null;
-  }
-
   /** Assigns a value to the model. */
   private _assignValue(value: D | null) {
     // We may get some incoming values before the model was
diff --git a/src/material/datepicker/datepicker-input.ts b/src/material/datepicker/datepicker-input.ts
index 0dbff5966c46..ba24bf7e2c6e 100644
--- a/src/material/datepicker/datepicker-input.ts
+++ b/src/material/datepicker/datepicker-input.ts
@@ -83,7 +83,7 @@ export class MatDatepickerInput<D> extends MatDatepickerInputBase<D | null, D>
   @Input()
   get min(): D | null { return this._min; }
   set min(value: D | null) {
-    this._min = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._min = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
     this._validatorOnChange();
   }
   private _min: D | null;
@@ -92,7 +92,7 @@ export class MatDatepickerInput<D> extends MatDatepickerInputBase<D | null, D>
   @Input()
   get max(): D | null { return this._max; }
   set max(value: D | null) {
-    this._max = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._max = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
     this._validatorOnChange();
   }
   private _max: D | null;
diff --git a/src/material/datepicker/month-view.ts b/src/material/datepicker/month-view.ts
index f9b7ccf95887..090329234adf 100644
--- a/src/material/datepicker/month-view.ts
+++ b/src/material/datepicker/month-view.ts
@@ -76,7 +76,9 @@ export class MatMonthView<D> implements AfterContentInit, OnDestroy {
   set activeDate(value: D) {
     const oldActiveDate = this._activeDate;
     const validDate =
-        this._getValidDateOrNull(this._dateAdapter.deserialize(value)) || this._dateAdapter.today();
+      this._dateAdapter.getValidDateOrNull(
+        this._dateAdapter.deserialize(value)
+      ) || this._dateAdapter.today();
     this._activeDate = this._dateAdapter.clampDate(validDate, this.minDate, this.maxDate);
     if (!this._hasSameMonthAndYear(oldActiveDate, this._activeDate)) {
       this._init();
@@ -91,7 +93,7 @@ export class MatMonthView<D> implements AfterContentInit, OnDestroy {
     if (value instanceof DateRange) {
       this._selected = value;
     } else {
-      this._selected = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+      this._selected = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
     }
 
     this._setRanges(this._selected);
@@ -102,7 +104,7 @@ export class MatMonthView<D> implements AfterContentInit, OnDestroy {
   @Input()
   get minDate(): D | null { return this._minDate; }
   set minDate(value: D | null) {
-    this._minDate = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._minDate = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _minDate: D | null;
 
@@ -110,7 +112,7 @@ export class MatMonthView<D> implements AfterContentInit, OnDestroy {
   @Input()
   get maxDate(): D | null { return this._maxDate; }
   set maxDate(value: D | null) {
-    this._maxDate = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._maxDate = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _maxDate: D | null;
 
@@ -412,14 +414,6 @@ export class MatMonthView<D> implements AfterContentInit, OnDestroy {
     return null;
   }
 
-  /**
-   * @param obj The object to check.
-   * @returns The given object if it is both a date instance and valid, otherwise null.
-   */
-  private _getValidDateOrNull(obj: any): D | null {
-    return (this._dateAdapter.isDateInstance(obj) && this._dateAdapter.isValid(obj)) ? obj : null;
-  }
-
   /** Determines whether the user has the RTL layout direction. */
   private _isRtl() {
     return this._dir && this._dir.value === 'rtl';
diff --git a/src/material/datepicker/multi-year-view.ts b/src/material/datepicker/multi-year-view.ts
index 587ab0125b8a..c2380da8137b 100644
--- a/src/material/datepicker/multi-year-view.ts
+++ b/src/material/datepicker/multi-year-view.ts
@@ -63,7 +63,9 @@ export class MatMultiYearView<D> implements AfterContentInit, OnDestroy {
   set activeDate(value: D) {
     let oldActiveDate = this._activeDate;
     const validDate =
-        this._getValidDateOrNull(this._dateAdapter.deserialize(value)) || this._dateAdapter.today();
+      this._dateAdapter.getValidDateOrNull(
+        this._dateAdapter.deserialize(value)
+      ) || this._dateAdapter.today();
     this._activeDate = this._dateAdapter.clampDate(validDate, this.minDate, this.maxDate);
 
     if (!isSameMultiYearView(
@@ -80,7 +82,7 @@ export class MatMultiYearView<D> implements AfterContentInit, OnDestroy {
     if (value instanceof DateRange) {
       this._selected = value;
     } else {
-      this._selected = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+      this._selected = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
     }
 
     this._setSelectedYear(value);
@@ -92,7 +94,7 @@ export class MatMultiYearView<D> implements AfterContentInit, OnDestroy {
   @Input()
   get minDate(): D | null { return this._minDate; }
   set minDate(value: D | null) {
-    this._minDate = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._minDate = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _minDate: D | null;
 
@@ -100,7 +102,7 @@ export class MatMultiYearView<D> implements AfterContentInit, OnDestroy {
   @Input()
   get maxDate(): D | null { return this._maxDate; }
   set maxDate(value: D | null) {
-    this._maxDate = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._maxDate = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _maxDate: D | null;
 
@@ -280,14 +282,6 @@ export class MatMultiYearView<D> implements AfterContentInit, OnDestroy {
     return false;
   }
 
-  /**
-   * @param obj The object to check.
-   * @returns The given object if it is both a date instance and valid, otherwise null.
-   */
-  private _getValidDateOrNull(obj: any): D | null {
-    return (this._dateAdapter.isDateInstance(obj) && this._dateAdapter.isValid(obj)) ? obj : null;
-  }
-
   /** Determines whether the user has the RTL layout direction. */
   private _isRtl() {
     return this._dir && this._dir.value === 'rtl';
diff --git a/src/material/datepicker/year-view.ts b/src/material/datepicker/year-view.ts
index f86b14f31eec..b6530b419940 100644
--- a/src/material/datepicker/year-view.ts
+++ b/src/material/datepicker/year-view.ts
@@ -60,7 +60,9 @@ export class MatYearView<D> implements AfterContentInit, OnDestroy {
   set activeDate(value: D) {
     let oldActiveDate = this._activeDate;
     const validDate =
-        this._getValidDateOrNull(this._dateAdapter.deserialize(value)) || this._dateAdapter.today();
+      this._dateAdapter.getValidDateOrNull(
+        this._dateAdapter.deserialize(value)
+      ) || this._dateAdapter.today();
     this._activeDate = this._dateAdapter.clampDate(validDate, this.minDate, this.maxDate);
     if (this._dateAdapter.getYear(oldActiveDate) !== this._dateAdapter.getYear(this._activeDate)) {
       this._init();
@@ -75,7 +77,7 @@ export class MatYearView<D> implements AfterContentInit, OnDestroy {
     if (value instanceof DateRange) {
       this._selected = value;
     } else {
-      this._selected = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+      this._selected = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
     }
 
     this._setSelectedMonth(value);
@@ -86,7 +88,7 @@ export class MatYearView<D> implements AfterContentInit, OnDestroy {
   @Input()
   get minDate(): D | null { return this._minDate; }
   set minDate(value: D | null) {
-    this._minDate = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._minDate = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _minDate: D | null;
 
@@ -94,7 +96,7 @@ export class MatYearView<D> implements AfterContentInit, OnDestroy {
   @Input()
   get maxDate(): D | null { return this._maxDate; }
   set maxDate(value: D | null) {
-    this._maxDate = this._getValidDateOrNull(this._dateAdapter.deserialize(value));
+    this._maxDate = this._dateAdapter.getValidDateOrNull(this._dateAdapter.deserialize(value));
   }
   private _maxDate: D | null;
 
@@ -317,14 +319,6 @@ export class MatYearView<D> implements AfterContentInit, OnDestroy {
     return false;
   }
 
-  /**
-   * @param obj The object to check.
-   * @returns The given object if it is both a date instance and valid, otherwise null.
-   */
-  private _getValidDateOrNull(obj: any): D | null {
-    return (this._dateAdapter.isDateInstance(obj) && this._dateAdapter.isValid(obj)) ? obj : null;
-  }
-
   /** Determines whether the user has the RTL layout direction. */
   private _isRtl() {
     return this._dir && this._dir.value === 'rtl';
diff --git a/tools/public_api_guard/material/core.d.ts b/tools/public_api_guard/material/core.d.ts
index 3838444717af..9026a50d2e43 100644
--- a/tools/public_api_guard/material/core.d.ts
+++ b/tools/public_api_guard/material/core.d.ts
@@ -67,6 +67,7 @@ export declare abstract class DateAdapter<D> {
     abstract getMonth(date: D): number;
     abstract getMonthNames(style: 'long' | 'short' | 'narrow'): string[];
     abstract getNumDaysInMonth(date: D): number;
+    getValidDateOrNull(obj: unknown): D | null;
     abstract getYear(date: D): number;
     abstract getYearName(date: D): string;
     abstract invalid(): D;