Port fast-head.js to TypeScript (#51401)

src/frame/middleware/context/context.ts

@@ -35,6 +35,8 @@ export default async function contextualize(
 
   const context: Context = {}
   req.context = context
+  console.log('CREATING CONTEXT')
+
   req.context.process = { env: {} }
 
   // define each context property explicitly for code-search friendliness

src/frame/middleware/fast-head.js → src/frame/middleware/fast-head.ts

@@ -1,6 +1,10 @@
+import type { Response, NextFunction } from 'express'
+
+import type { ExtendedRequest } from '@/types'
 import { defaultCacheControl } from './cache-control.js'
 
-export default function fastHead(req, res, next) {
+export default function fastHead(req: ExtendedRequest, res: Response, next: NextFunction) {
+  if (!req.context) throw new Error('request is not contextualized')
   const { context } = req
   const { page } = context
   if (page) {

src/frame/middleware/index.ts

@@ -56,7 +56,7 @@ import assetPreprocessing from '@/assets/middleware/asset-preprocessing'
 import archivedAssetRedirects from '@/archives/middleware/archived-asset-redirects'
 import favicons from './favicons.js'
 import setStaticAssetCaching from '@/assets/middleware/static-asset-caching'
-import fastHead from './fast-head.js'
+import fastHead from './fast-head'
 import fastlyCacheTest from './fastly-cache-test.js'
 import trailingSlashes from './trailing-slashes.js'
 import fastlyBehavior from './fastly-behavior.js'