From 29db4f2f85ecc02901d634527ac58652c9a72102 Mon Sep 17 00:00:00 2001
From: KirtiRamchandani <kirtiar15502@gmail.com>
Date: Mon, 25 May 2026 08:52:05 +0530
Subject: [PATCH] fix: preserve radio state after deferred upgrade

---
 .../src/radio-group/radio-group.base.ts       | 28 ++++++-
 .../src/radio-group/radio-group.spec.ts       | 79 +++++++++++++++++++
 2 files changed, 104 insertions(+), 3 deletions(-)

diff --git a/packages/web-components/src/radio-group/radio-group.base.ts b/packages/web-components/src/radio-group/radio-group.base.ts
index 48161953041618..e3c1c2b18eb2a6 100644
--- a/packages/web-components/src/radio-group/radio-group.base.ts
+++ b/packages/web-components/src/radio-group/radio-group.base.ts
@@ -1,6 +1,5 @@
-import { attr, FASTElement, Observable, observable } from '@microsoft/fast-element';
+import { attr, FASTElement, Observable, observable, Updates } from '@microsoft/fast-element';
 import type { Radio } from '../radio/radio.js';
-import { isRadio } from '../radio/radio.options.js';
 import { RadioGroupOrientation } from './radio-group.options.js';
 
 /**
@@ -218,6 +217,14 @@ export class BaseRadioGroup extends FASTElement {
   @observable
   slottedRadios!: Radio[];
 
+  private static isUpgradedRadio(element: Element): element is Radio {
+    return element.localName.endsWith('-radio') && '$fastController' in element;
+  }
+
+  private getRadioDescendants(): Radio[] {
+    return [...this.querySelectorAll('*')].filter(BaseRadioGroup.isUpgradedRadio);
+  }
+
   /**
    * Updates the radios collection when the slotted radios change.
    *
@@ -225,7 +232,22 @@ export class BaseRadioGroup extends FASTElement {
    * @param next - the current slotted radios
    */
   slottedRadiosChanged(prev: Radio[] | undefined, next: Radio[]): void {
-    this.radios = [...this.querySelectorAll('*')].filter(x => isRadio(x)) as Radio[];
+    Updates.enqueue(() => {
+      const elements = [...this.querySelectorAll('*')];
+      this.radios = this.getRadioDescendants();
+
+      for (const tagName of new Set(
+        elements
+          .filter(x => x.localName.endsWith('-radio') && !BaseRadioGroup.isUpgradedRadio(x))
+          .map(x => x.localName),
+      )) {
+        customElements.whenDefined(tagName).then(() => {
+          if (this.isConnected) {
+            this.radios = this.getRadioDescendants();
+          }
+        });
+      }
+    });
   }
 
   /**
diff --git a/packages/web-components/src/radio-group/radio-group.spec.ts b/packages/web-components/src/radio-group/radio-group.spec.ts
index 6b581d079c232b..1f5ac64465f44a 100644
--- a/packages/web-components/src/radio-group/radio-group.spec.ts
+++ b/packages/web-components/src/radio-group/radio-group.spec.ts
@@ -4,6 +4,8 @@ import { tagName as RadioTagName } from '../radio/radio.options.js';
 import type { RadioGroup } from './radio-group.js';
 import { tagName } from './radio-group.options.js';
 
+const sourceBaseUrl = `/@fs${new URL('../', import.meta.url).pathname}`;
+
 test.describe('RadioGroup', () => {
   test.use({
     tagName,
@@ -250,6 +252,83 @@ test.describe('RadioGroup', () => {
     await expect(radios.nth(2)).toHaveJSProperty('checked', false);
   });
 
+  test('should preserve checked state when radios upgrade after the group', async ({ page }) => {
+    await page.goto('/');
+
+    const result = await page.evaluate(async sourceBaseUrl => {
+      const id = Date.now().toString(36);
+      const groupTagName = `upgrade-${id}-radio-group`;
+      const radioTagName = `upgrade-${id}-radio`;
+
+      const importModule = (path: string): Promise<Record<string, unknown>> => import(path);
+      const [
+        radioGroupModule,
+        radioGroupTemplateModule,
+        radioGroupStylesModule,
+        radioModule,
+        radioTemplateModule,
+        radioStylesModule,
+      ] = await Promise.all([
+        importModule(`${sourceBaseUrl}radio-group/radio-group.ts`),
+        importModule(`${sourceBaseUrl}radio-group/radio-group.template.ts`),
+        importModule(`${sourceBaseUrl}radio-group/radio-group.styles.ts`),
+        importModule(`${sourceBaseUrl}radio/radio.ts`),
+        importModule(`${sourceBaseUrl}radio/radio.template.ts`),
+        importModule(`${sourceBaseUrl}radio/radio.styles.ts`),
+      ]);
+
+      const RadioGroup = radioGroupModule.RadioGroup as {
+        compose(options: Record<string, unknown>): { define(registry: CustomElementRegistry): void };
+      };
+      const Radio = radioModule.Radio as {
+        compose(options: Record<string, unknown>): { define(registry: CustomElementRegistry): void };
+      };
+
+      document.body.innerHTML = /* html */ `
+        <${groupTagName} value="bar">
+          <${radioTagName} value="foo"></${radioTagName}>
+          <${radioTagName} value="bar"></${radioTagName}>
+          <${radioTagName} value="baz"></${radioTagName}>
+        </${groupTagName}>
+      `;
+
+      RadioGroup.compose({
+        name: groupTagName,
+        template: radioGroupTemplateModule.template,
+        styles: radioGroupStylesModule.styles,
+      }).define(customElements);
+
+      const group = document.querySelector(groupTagName);
+      if (!group) {
+        throw new Error('Expected radio group to exist.');
+      }
+
+      customElements.upgrade(group);
+
+      Radio.compose({
+        name: radioTagName,
+        template: radioTemplateModule.template,
+        styles: radioStylesModule.styles,
+      }).define(customElements);
+
+      await customElements.whenDefined(groupTagName);
+      await customElements.whenDefined(radioTagName);
+      await new Promise(requestAnimationFrame);
+
+      const checkedRadio = document.querySelector(`${radioTagName}[value="bar"]`) as HTMLElement & {
+        checked: boolean;
+      };
+
+      return {
+        checked: checkedRadio.checked,
+        hasOwnChecked: Object.prototype.hasOwnProperty.call(checkedRadio, 'checked'),
+      };
+    }, sourceBaseUrl);
+
+    expect(result.checked).toBe(true);
+    expect(result.hasOwnChecked).toBe(false);
+  });
+
   test('radio should remain checked after it is set to disabled and uncheck when a new radio is checked', async ({
     fastPage,
     page,