fix(webchannel): Send 'can_link_account' on email-first for isSync/isFirefoxNonSync when fxa_status resolves

Because:
* On email-first, we are sending 'can_link_account' before the fxa_status result has resolved, which tells us whether that Firefox supports sending the UID in can_link_account. This is problematic because we should NOT be sending the merge warning at this point if Firefox does support the UID capability

This commit:
* Sets the default of 'supportsCanLinkAccountUid' to 'undefined' until fxa_status is received, and does not auto-submit the email on email-first if 'supportsCanLinkAccountUid' is undefined

fixes FXA-13002

Author: LZoog

packages/fxa-settings/src/lib/hooks/useFxAStatus/index.tsx

@@ -41,7 +41,7 @@ export function useFxAStatus(integration: FxAStatusIntegration) {
   const [supportsKeysOptionalLogin, setSupportsKeysOptionalLogin] =
     useState<boolean>(false);
   const [supportsCanLinkAccountUid, setSupportsCanLinkAccountUid] =
-    useState<boolean>(false);
+    useState<boolean | undefined>(undefined);
 
   useEffect(() => {
     // This sends a web channel message to the browser to prompt a response

packages/fxa-settings/src/lib/hooks/useFxAStatus/mocks.tsx

@@ -7,11 +7,11 @@ import { getSyncEngineIds, syncEngineConfigs } from '../../sync-engines';
 export function mockUseFxAStatus({
   offeredSyncEnginesOverride,
   supportsKeysOptionalLogin = false,
-  supportsCanLinkAccountUid = false,
+  supportsCanLinkAccountUid,
 }: {
   offeredSyncEnginesOverride?: ReturnType<typeof getSyncEngineIds>;
   supportsKeysOptionalLogin?: boolean;
-  supportsCanLinkAccountUid?: boolean;
+  supportsCanLinkAccountUid?: boolean | undefined;
 } = {}) {
   const offeredSyncEngineConfigs = syncEngineConfigs;
   const offeredSyncEngines =

packages/fxa-settings/src/pages/Index/container.test.tsx

@@ -7,7 +7,6 @@ import * as IndexModule from './index';
 import * as ReactUtils from 'fxa-react/lib/utils';
 import * as cache from '../../lib/cache';
 
-import React from 'react';
 import { waitFor } from '@testing-library/react';
 import { LocationProvider } from '@reach/router';
 import { useValidatedQueryParams } from '../../lib/hooks/useValidate';
@@ -971,6 +970,75 @@ describe('IndexContainer', () => {
           expect(currentIndexProps?.errorBannerMessage).toBeDefined();
         });
       });
+
+      describe('useFxAStatusResult.supportsCanLinkAccountUid and processEmailSubmission', () => {
+        beforeEach(() => {
+          jest.spyOn(cache, 'currentAccount').mockReturnValue({
+            uid: 'abc123',
+            email: MOCK_EMAIL,
+            lastLogin: Date.now(),
+          });
+        });
+
+        it('shows loading spinner and does not call fxaCanLinkAccount when supportsCanLinkAccountUid is undefined', async () => {
+          mockUseFxAStatusResult = mockUseFxAStatus({
+            supportsCanLinkAccountUid: undefined,
+          });
+
+          const { getByText } = renderWithLocalizationProvider(
+            <LocationProvider>
+              <IndexContainer
+                integration={integration}
+                serviceName={MozServices.FirefoxSync}
+                useFxAStatusResult={mockUseFxAStatusResult}
+              />
+            </LocationProvider>
+          );
+
+          expect(getByText('LoadingSpinner')).toBeInTheDocument();
+          expect(firefox.fxaCanLinkAccount).not.toHaveBeenCalled();
+        });
+
+        it('does not call fxaCanLinkAccount when supportsCanLinkAccountUid is true', async () => {
+          mockUseFxAStatusResult = mockUseFxAStatus({
+            supportsCanLinkAccountUid: true,
+          });
+
+          renderWithLocalizationProvider(
+            <LocationProvider>
+              <IndexContainer
+                integration={integration}
+                serviceName={MozServices.FirefoxSync}
+                useFxAStatusResult={mockUseFxAStatusResult}
+              />
+            </LocationProvider>
+          );
+
+          await waitFor(() => {
+            expect(firefox.fxaCanLinkAccount).not.toHaveBeenCalled();
+          });
+        });
+
+        it('calls fxaCanLinkAccount when supportsCanLinkAccountUid is false', async () => {
+          mockUseFxAStatusResult = mockUseFxAStatus({
+            supportsCanLinkAccountUid: false,
+          });
+
+          renderWithLocalizationProvider(
+            <LocationProvider>
+              <IndexContainer
+                integration={integration}
+                serviceName={MozServices.FirefoxSync}
+                useFxAStatusResult={mockUseFxAStatusResult}
+              />
+            </LocationProvider>
+          );
+
+          await waitFor(() => {
+            expect(firefox.fxaCanLinkAccount).toHaveBeenCalled();
+          });
+        });
+      });
     });
   });
 });

packages/fxa-settings/src/pages/Index/container.tsx

@@ -271,12 +271,20 @@ const IndexContainer = ({
     if (isUnsupportedContext(integration.data.context)) {
       hardNavigate('/update_firefox', {}, true);
     } else if (shouldTrySuggestedEmail && !attemptedEmailAutoSubmit.current) {
-      // Without this, can_link_account can fire multiple times due to calling it in a `useEffect`,
-      // causing multiple sync warnings to be displayed. This ensures it is called once.
-      attemptedEmailAutoSubmit.current = true;
       // Must be in an async function or else `setIsLoading(false)` can be called prematurely with
       // the next render, before async actions in `processEmailSubmission` have finished
       (async () => {
+        if (integration.isSync() || integration.isFirefoxNonSync()) {
+          // Wait for this to resolve before calling 'processEmailSubmission'.
+          // Otherwise, a merge warning may show on email-first for newer Fx versions
+          // that support "can link account" by UID.
+          if (useFxAStatusResult.supportsCanLinkAccountUid === undefined) {
+            return;
+          }
+        }
+        // Without this, can_link_account can fire multiple times due to calling it in a `useEffect`,
+        // causing multiple sync warnings to be displayed. This ensures it is called once.
+        attemptedEmailAutoSubmit.current = true;
         await processEmailSubmission(suggestedEmail, false);
       })();
     } else {
@@ -290,6 +298,7 @@ const IndexContainer = ({
     shouldTrySuggestedEmail,
     integration.data.context,
     integration,
+    useFxAStatusResult.supportsCanLinkAccountUid,
   ]);
 
   useEffect(() => {