fix(cdk/listbox): incorrectly validating preselected value (#25893)

In #25856 the check that verifies the validity of the form control value was moved into `writeValue`. This works as expected for assignments after initialization, but it throws an error incorrectly if there is a preselected value, because `writeValue` will be called before the options are available.

These changes resolve the issue by checking that the options have been initialized before throwing the error.

Author: crisbeto

src/cdk/listbox/listbox.spec.ts

@@ -883,6 +883,18 @@ describe('CdkOption and CdkListbox', () => {
         fixture.detectChanges();
       }).toThrowError('Listbox has selected values that do not match any of its options.');
     });
+
+    it('should not throw on init with a preselected form control and a dynamic set of options', () => {
+      expect(() => {
+        setupComponent(ListboxWithPreselectedFormControl, [ReactiveFormsModule]);
+      }).not.toThrow();
+    });
+
+    it('should throw on init if the preselected value is invalid', () => {
+      expect(() => {
+        setupComponent(ListboxWithInvalidPreselectedFormControl, [ReactiveFormsModule]);
+      }).toThrowError('Listbox has selected values that do not match any of its options.');
+    });
   });
 });
 
@@ -955,6 +967,30 @@ class ListboxWithFormControl {
   isActiveDescendant = false;
 }
 
+@Component({
+  template: `
+    <div cdkListbox [formControl]="formControl">
+      <div *ngFor="let option of options" [cdkOption]="option">{{option}}</div>
+    </div>
+  `,
+})
+class ListboxWithPreselectedFormControl {
+  options = ['a', 'b', 'c'];
+  formControl = new FormControl('c');
+}
+
+@Component({
+  template: `
+    <div cdkListbox [formControl]="formControl">
+      <div *ngFor="let option of options" [cdkOption]="option">{{option}}</div>
+    </div>
+  `,
+})
+class ListboxWithInvalidPreselectedFormControl {
+  options = ['a', 'b', 'c'];
+  formControl = new FormControl('d');
+}
+
 @Component({
   template: `
     <ul cdkListbox>

src/cdk/listbox/listbox.ts

@@ -422,6 +422,7 @@ export class CdkListbox<T = unknown> implements AfterContentInit, OnDestroy, Con
   ngAfterContentInit() {
     if (typeof ngDevMode === 'undefined' || ngDevMode) {
       this._verifyNoOptionValueCollisions();
+      this._verifyOptionValues();
     }
 
     this._initKeyManager();
@@ -561,19 +562,7 @@ export class CdkListbox<T = unknown> implements AfterContentInit, OnDestroy, Con
    */
   writeValue(value: readonly T[]): void {
     this._setSelection(value);
-
-    if (typeof ngDevMode === 'undefined' || ngDevMode) {
-      const selected = this.selectionModel.selected;
-      const invalidValues = this._getInvalidOptionValues(selected);
-
-      if (!this.multiple && selected.length > 1) {
-        throw Error('Listbox cannot have more than one selected value in multi-selection mode.');
-      }
-
-      if (invalidValues.length) {
-        throw Error('Listbox has selected values that do not match any of its options.');
-      }
-    }
+    this._verifyOptionValues();
   }
 
   /**
@@ -924,6 +913,22 @@ export class CdkListbox<T = unknown> implements AfterContentInit, OnDestroy, Con
     });
   }
 
+  /** Verifies that the option values are valid. */
+  private _verifyOptionValues() {
+    if (this.options && (typeof ngDevMode === 'undefined' || ngDevMode)) {
+      const selected = this.selectionModel.selected;
+      const invalidValues = this._getInvalidOptionValues(selected);
+
+      if (!this.multiple && selected.length > 1) {
+        throw Error('Listbox cannot have more than one selected value in multi-selection mode.');
+      }
+
+      if (invalidValues.length) {
+        throw Error('Listbox has selected values that do not match any of its options.');
+      }
+    }
+  }
+
   /**
    * Coerces a value into an array representing a listbox selection.
    * @param value The value to coerce