re-read content on every request (github#30646)

Author: Peter Bengtsson

contributing/development.md

@@ -22,7 +22,7 @@ npm run build
 npm start
 ```
 
-You should now have a running server! Visit [localhost:4000](http://localhost:4000) in your browser. It will automatically restart as you make changes to site content.
+You should now have a running server! Visit [localhost:4000](http://localhost:4000) in your browser.
 
 When you're ready to stop your local server, type <kbd>Ctrl</kbd>+<kbd>C</kbd> in your terminal window.
 

middleware/find-page.js

@@ -1,5 +1,32 @@
-export default function findPage(req, res, next) {
-  const page = req.context.pages[req.pagePath]
+import { fileURLToPath } from 'url'
+import path from 'path'
+import { existsSync } from 'fs'
+
+import Page from '../lib/page.js'
+import { languageKeys } from '../lib/languages.js'
+
+const languagePrefixRegex = new RegExp(`^/(${languageKeys.join('|')})(/|$)`)
+const englishPrefixRegex = /^\/en(\/|$)/
+const __dirname = path.dirname(fileURLToPath(import.meta.url))
+const CONTENT_ROOT = path.posix.join(__dirname, '..', 'content')
+
+export default async function findPage(
+  req,
+  res,
+  next,
+  // Express won't execute these but it makes it easier to unit test
+  // the middleware.
+  { isDev = process.env.NODE_ENV === 'development', contentRoot = CONTENT_ROOT } = {}
+) {
+  // Filter out things like `/will/redirect` or `/_next/data/...`
+  if (!languagePrefixRegex.test(req.pagePath)) {
+    return next()
+  }
+
+  const page =
+    isDev && englishPrefixRegex.test(req.pagePath)
+      ? await rereadByPath(req.pagePath, contentRoot, req.context.currentVersion)
+      : req.context.pages[req.pagePath]
 
   if (page) {
     req.context.page = page
@@ -8,3 +35,27 @@ export default function findPage(req, res, next) {
 
   return next()
 }
+
+async function rereadByPath(uri, contentRoot, currentVersion) {
+  const languageCode = uri.match(languagePrefixRegex)[1]
+  const withoutLanguage = uri.replace(languagePrefixRegex, '/')
+  const withoutVersion = withoutLanguage.replace(`/${currentVersion}/`, '/')
+  // TODO: Support loading translations the same way.
+  // NOTE: No one is going to test translations like this in development
+  // but perhaps one day we can always and only do these kinds of lookups
+  // at runtime.
+  const possible = path.join(contentRoot, withoutVersion)
+  const filePath = existsSync(possible) ? path.join(possible, 'index.md') : possible + '.md'
+  const relativePath = path.relative(contentRoot, filePath)
+  const basePath = contentRoot
+
+  // Remember, the Page.init() can return a Promise that resolves to falsy
+  // if it can't read the file in from disk. E.g. a request for /en/non/existent.
+  // In other words, it's fine if it can't be read from disk. It'll get
+  // handled and turned into a nice 404 message.
+  return await Page.init({
+    basePath,
+    relativePath,
+    languageCode,
+  })
+}

middleware/index.js

@@ -222,7 +222,7 @@ export default function (app) {
   app.use(instrument(handleRedirects, './redirects/handle-redirects')) // Must come before contextualizers
 
   // *** Config and context for rendering ***
-  app.use(instrument(findPage, './find-page')) // Must come before archived-enterprise-versions, breadcrumbs, featured-links, products, render-page
+  app.use(asyncMiddleware(instrument(findPage, './find-page'))) // Must come before archived-enterprise-versions, breadcrumbs, featured-links, products, render-page
   app.use(instrument(blockRobots, './block-robots'))
 
   // Check for a dropped connection before proceeding

nodemon.json

@@ -5,6 +5,7 @@
     "script",
     "translations",
     "stylesheets",
-    "tests"
+    "tests",
+    "content"
   ]
 }

tests/unit/find-page-middleware.js

@@ -0,0 +1,89 @@
+import { fileURLToPath } from 'url'
+import path from 'path'
+import http from 'http'
+
+import { expect, describe, test } from '@jest/globals'
+
+import Page from '../../lib/page.js'
+import findPage from '../../middleware/find-page.js'
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url))
+
+function makeRequestResponse(url, currentVersion = 'free-pro-team@latest') {
+  const req = new http.IncomingMessage(null)
+  req.method = 'GET'
+  req.url = url
+  req.path = url
+  req.cookies = {}
+  req.headers = {}
+
+  // Custom keys on the request
+  req.pagePath = url
+  req.context = {}
+  req.context.currentVersion = currentVersion
+  req.context.pages = {}
+
+  return [req, new http.ServerResponse(req)]
+}
+
+describe('find page middleware', () => {
+  test('attaches page on req.context', async () => {
+    const url = '/en/foo/bar'
+    const [req, res] = makeRequestResponse(url)
+    req.context.pages = {
+      '/en/foo/bar': await Page.init({
+        relativePath: 'page-with-redirects.md',
+        basePath: path.join(__dirname, '../fixtures'),
+        languageCode: 'en',
+      }),
+    }
+
+    let nextCalls = 0
+    await findPage(req, res, () => {
+      nextCalls++
+    })
+    expect(nextCalls).toBe(1)
+    expect(req.context.page).toBeInstanceOf(Page)
+  })
+
+  test('does not attach page on req.context if not found', async () => {
+    const [req, res] = makeRequestResponse('/en/foo/bar')
+
+    let nextCalls = 0
+    await findPage(req, res, () => {
+      nextCalls++
+    })
+    expect(nextCalls).toBe(1)
+    expect(req.context.page).toBe(undefined)
+  })
+
+  test('re-reads from disk if in development mode', async () => {
+    const [req, res] = makeRequestResponse('/en/page-with-redirects')
+
+    await findPage(req, res, () => {}, {
+      isDev: true,
+      contentRoot: path.join(__dirname, '../fixtures'),
+    })
+    expect(req.context.page).toBeInstanceOf(Page)
+  })
+
+  test('finds it for non-fpt version URLS', async () => {
+    const [req, res] = makeRequestResponse('/en/page-with-redirects', 'enterprise-cloud@latest')
+
+    await findPage(req, res, () => {}, {
+      isDev: true,
+      contentRoot: path.join(__dirname, '../fixtures'),
+    })
+    expect(req.context.page).toBeInstanceOf(Page)
+  })
+
+  test('re-reads from disk if in development mode and finds nothing', async () => {
+    const [req, res] = makeRequestResponse('/en/never/heard/of')
+
+    await findPage(req, res, () => {}, {
+      isDev: true,
+      contentRoot: path.join(__dirname, '../fixtures'),
+    })
+    expect(req.context.page).toBe(undefined)
+  })
+})