fix: [#1587] Fixes the HTMLInputElement.defaultChecked property (#1656)

Author: capricorn86

packages/happy-dom/src/nodes/html-input-element/HTMLInputElement.ts

@@ -41,7 +41,6 @@ export default class HTMLInputElement extends HTMLElement {
 	public [PropertySymbol.value] = null;
 	public [PropertySymbol.height] = 0;
 	public [PropertySymbol.width] = 0;
-	public [PropertySymbol.defaultChecked] = false;
 	public [PropertySymbol.checked]: boolean | null = null;
 	public [PropertySymbol.validationMessage] = '';
 	public [PropertySymbol.validity] = new ValidityState(this);
@@ -62,7 +61,7 @@ export default class HTMLInputElement extends HTMLElement {
 	 * @returns Default checked.
 	 */
 	public get defaultChecked(): boolean {
-		return this[PropertySymbol.defaultChecked];
+		return this.hasAttribute('checked');
 	}
 
 	/**
@@ -71,7 +70,11 @@ export default class HTMLInputElement extends HTMLElement {
 	 * @param defaultChecked Default checked.
 	 */
 	public set defaultChecked(defaultChecked: boolean) {
-		this[PropertySymbol.defaultChecked] = defaultChecked;
+		if (defaultChecked) {
+			this.setAttribute('checked', '');
+		} else {
+			this.removeAttribute('checked');
+		}
 	}
 
 	/**
@@ -1341,7 +1344,6 @@ export default class HTMLInputElement extends HTMLElement {
 		clone[PropertySymbol.value] = this[PropertySymbol.value];
 		clone[PropertySymbol.height] = this[PropertySymbol.height];
 		clone[PropertySymbol.width] = this[PropertySymbol.width];
-		clone[PropertySymbol.defaultChecked] = this[PropertySymbol.defaultChecked];
 		clone[PropertySymbol.files] = <FileList>this[PropertySymbol.files].slice();
 		clone.#selectionStart = this.#selectionStart;
 		clone.#selectionEnd = this.#selectionEnd;

packages/happy-dom/test/nodes/html-input-element/HTMLInputElement.test.ts

@@ -1065,6 +1065,23 @@ describe('HTMLInputElement', () => {
 		});
 	});
 
+	describe('get defaultChecked()', () => {
+		it('Returns true if the attribute "checked" has been set.', () => {
+			expect(element.defaultChecked).toBe(false);
+			element.setAttribute('checked', '');
+			expect(element.defaultChecked).toBe(true);
+		});
+	});
+
+	describe('set defaultChecked()', () => {
+		it('Sets the attribute "checked".', () => {
+			element.defaultChecked = true;
+			expect(element.getAttribute('checked')).toBe('');
+			element.defaultChecked = false;
+			expect(element.getAttribute('checked')).toBe(null);
+		});
+	});
+
 	describe('setCustomValidity()', () => {
 		it('Returns validation message.', () => {
 			element.setCustomValidity('Error message');