Call migration store option API after siteCreationStep if it's from m…

…igration plugin (#73080)

client/landing/stepper/declarative-flow/internals/steps-repository/import/helper.ts

@@ -8,6 +8,7 @@ import {
 	getWpOrgImporterUrl,
 } from 'calypso/blocks/import/util';
 import { WPImportOption } from 'calypso/blocks/importer/wordpress/types';
+import wpcom from 'calypso/lib/wp';
 import { BASE_ROUTE } from './config';
 
 export function getFinalImporterUrl(
@@ -62,3 +63,18 @@ export function generateStepPath( stepName: string, stepSectionName?: string ) {
 
 	return camelCase( path ) as string;
 }
+
+export async function addTempSiteToSourceOption( targetBlogId: number, sourceSiteSlug: string ) {
+	return wpcom.req
+		.post( {
+			path: `/migrations/from-source/${ sourceSiteSlug }`,
+			apiNamespace: 'wpcom/v2',
+			body: {
+				target_blog_id: targetBlogId,
+			},
+		} )
+		.catch( ( error: Error ) => {
+			// eslint-disable-next-line no-console
+			console.error( 'Unable to store option in source site', error );
+		} );
+}

client/landing/stepper/declarative-flow/internals/steps-repository/site-creation-step/index.tsx

@@ -28,6 +28,7 @@ import {
 	getSignupCompleteSlug,
 } from 'calypso/signup/storageUtils';
 import { getCurrentUserName } from 'calypso/state/current-user/selectors';
+import { addTempSiteToSourceOption } from '../import/helper';
 import type { Step } from '../../types';
 
 import './styles.scss';
@@ -122,6 +123,13 @@ const SiteCreationStep: Step = function SiteCreationStep( { navigation, flow, da
 			await addProductsToCart( site?.siteSlug as string, flow as string, productCartItems );
 		}
 
+		if ( isMigrationFlow( flow ) ) {
+			const search = window.location.search;
+			const sourceSiteSlug = new URLSearchParams( search ).get( 'from' );
+			// Store temporary target blog id to source site option
+			await addTempSiteToSourceOption( site?.siteId as number, sourceSiteSlug as string );
+		}
+
 		return {
 			siteSlug: site?.siteSlug,
 			goToCheckout: Boolean( planCartItem ),