Fix _next loading to avoid error on initial routing (#48553)

src/frame/components/context/MainContext.tsx

@@ -97,7 +97,7 @@ export type MainContextT = {
     href: string
   }
   currentProduct?: ProductT
-  currentLayoutName: string
+  currentLayoutName?: string
   isHomepageVersion: boolean
   data: DataT
   error: string
@@ -120,7 +120,7 @@ export type MainContextT = {
     hidden: boolean
     noEarlyAccessBanner: boolean
     applicableVersions: string[]
-  }
+  } | null
 
   enterpriseServerVersions: Array<string>
 
@@ -172,10 +172,9 @@ export const getMainContext = async (req: any, res: any): Promise<MainContextT>
     delete req.context.site.data.ui.ms
   }
 
-  if (!req.context.page) {
-    throw new Error(`No page context (${req.url})`)
-  }
-  const { documentType } = req.context.page
+  const { page } = req.context
+
+  const documentType = page ? (page.documentType as string) : undefined
 
   const ui: UIStrings = {}
   addUINamespaces(req, ui, DEFAULT_UI_NAMESPACES)
@@ -210,11 +209,24 @@ export const getMainContext = async (req: any, res: any): Promise<MainContextT>
   // as a full version string if the release candidate is set.
   const releaseCandidateVersion = releaseCandidate ? `enterprise-server@${releaseCandidate}` : null
 
-  return {
+  const pageInfo =
+    (page && {
+      documentType,
+      type: req.context.page.type || null,
+      title: req.context.page.title,
+      fullTitle: req.context.page.fullTitle || null,
+      topics: req.context.page.topics || [],
+      introPlainText: req.context.page?.introPlainText || null,
+      applicableVersions: req.context.page?.permalinks.map((obj: any) => obj.pageVersion) || [],
+      hidden: req.context.page.hidden || false,
+      noEarlyAccessBanner: req.context.page.noEarlyAccessBanner || false,
+    }) ||
+    null
+
+  const props: MainContextT = {
     breadcrumbs: req.context.breadcrumbs || {},
     communityRedirect: req.context.page?.communityRedirect || {},
     currentProduct: req.context.productMap[req.context.currentProduct] || null,
-    currentLayoutName: req.context.currentLayoutName,
     isHomepageVersion: req.context.page?.documentType === 'homepage',
     error: req.context.error ? req.context.error.toString() : '',
     data: {
@@ -230,18 +242,7 @@ export const getMainContext = async (req: any, res: any): Promise<MainContextT>
     },
     currentCategory: req.context.currentCategory || '',
     currentPathWithoutLanguage: req.context.currentPathWithoutLanguage,
-    relativePath: req.context.page?.relativePath,
-    page: {
-      documentType,
-      type: req.context.page.type || null,
-      title: req.context.page.title,
-      fullTitle: req.context.page.fullTitle,
-      topics: req.context.page.topics || [],
-      introPlainText: req.context.page?.introPlainText,
-      applicableVersions: req.context.page?.permalinks.map((obj: any) => obj.pageVersion) || [],
-      hidden: req.context.page.hidden || false,
-      noEarlyAccessBanner: req.context.page.noEarlyAccessBanner || false,
-    },
+    page: pageInfo,
     enterpriseServerReleases: pick(req.context.enterpriseServerReleases, [
       'isOldestReleaseDeprecated',
       'oldestSupported',
@@ -267,6 +268,14 @@ export const getMainContext = async (req: any, res: any): Promise<MainContextT>
     status: res.statusCode,
     fullUrl: req.protocol + '://' + req.get('host') + req.originalUrl,
   }
+
+  if (req.context.currentLayoutName) {
+    props.currentLayoutName = req.context.currentLayoutName
+  }
+  if (req.context.page?.relativePath) {
+    props.relativePath = req.context.page.relativePath
+  }
+  return props
 }
 
 export const MainContext = createContext<MainContextT | null>(null)