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next.js/server/on-demand-entry-handler.js

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import DynamicEntryPlugin from 'webpack/lib/DynamicEntryPlugin'
import { EventEmitter } from 'events'
import { join } from 'path'
import { parse } from 'url'
import resolvePath from './resolve'
import touch from 'touch'
import { MATCH_ROUTE_NAME, IS_BUNDLED_PAGE } from './utils'
const ADDED = Symbol('added')
const BUILDING = Symbol('building')
const BUILT = Symbol('built')
export default function onDemandEntryHandler (devMiddleware, compiler, {
dir,
dev,
reload,
maxInactiveAge = 1000 * 25
}) {
let entries = {}
let lastAccessPages = ['']
let doneCallbacks = new EventEmitter()
const invalidator = new Invalidator(devMiddleware)
let touchedAPage = false
let reloading = false
let stopped = false
let reloadCallbacks = new EventEmitter()
compiler.plugin('make', function (compilation, done) {
invalidator.startBuilding()
const allEntries = Object.keys(entries).map((page) => {
const { name, entry } = entries[page]
entries[page].status = BUILDING
return addEntry(compilation, this.context, name, entry)
})
Promise.all(allEntries)
.then(() => done())
.catch(done)
})
compiler.plugin('done', function (stats) {
const { compilation } = stats
const hardFailedPages = compilation.errors
.filter(e => {
// Make sure to only pick errors which marked with missing modules
const hasNoModuleFoundError = /ENOENT/.test(e.message) || /Module not found/.test(e.message)
if (!hasNoModuleFoundError) return false
// The page itself is missing. So this is a failed page.
if (IS_BUNDLED_PAGE.test(e.module.name)) return true
// No dependencies means this is a top level page.
// So this is a failed page.
return e.module.dependencies.length === 0
})
.map(e => e.module.chunks)
.reduce((a, b) => [...a, ...b], [])
.map(c => {
const pageName = MATCH_ROUTE_NAME.exec(c.name)[1]
return normalizePage(`/${pageName}`)
})
// Call all the doneCallbacks
Object.keys(entries).forEach((page) => {
const entryInfo = entries[page]
if (entryInfo.status !== BUILDING) return
// With this, we are triggering a filesystem based watch trigger
// It'll memorize some timestamp related info related to common files used
// in the page
// That'll reduce the page building time significantly.
if (!touchedAPage) {
setTimeout(() => {
touch.sync(entryInfo.pathname)
}, 1000)
touchedAPage = true
}
entryInfo.status = BUILT
entries[page].lastActiveTime = Date.now()
doneCallbacks.emit(page)
})
invalidator.doneBuilding()
if (hardFailedPages.length > 0 && !reloading) {
console.log(`> Reloading webpack due to inconsistant state of pages(s): ${hardFailedPages.join(', ')}`)
reloading = true
reload()
.then(() => {
console.log('> Webpack reloaded.')
reloadCallbacks.emit('done')
stop()
})
.catch(err => {
console.error(`> Webpack reloading failed: ${err.message}`)
console.error(err.stack)
process.exit(1)
})
}
})
const disposeHandler = setInterval(function () {
if (stopped) return
disposeInactiveEntries(devMiddleware, entries, lastAccessPages, maxInactiveAge)
}, 5000)
function stop () {
clearInterval(disposeHandler)
stopped = true
doneCallbacks = null
reloadCallbacks = null
}
return {
waitUntilReloaded () {
if (!reloading) return Promise.resolve(true)
return new Promise((resolve) => {
reloadCallbacks.once('done', function () {
resolve()
})
})
},
async ensurePage (page) {
await this.waitUntilReloaded()
page = normalizePage(page)
const pagePath = join(dir, 'pages', page)
const pathname = await resolvePath(pagePath)
const name = join('bundles', pathname.substring(dir.length))
const entry = [`${pathname}?entry`]
await new Promise((resolve, reject) => {
const entryInfo = entries[page]
if (entryInfo) {
if (entryInfo.status === BUILT) {
resolve()
return
}
if (entryInfo.status === BUILDING) {
doneCallbacks.on(page, processCallback)
return
}
}
console.log(`> Building page: ${page}`)
entries[page] = { name, entry, pathname, status: ADDED }
doneCallbacks.on(page, processCallback)
invalidator.invalidate()
function processCallback (err) {
if (err) return reject(err)
resolve()
}
})
},
middleware () {
return (req, res, next) => {
if (stopped) {
// If this handler is stopped, we need to reload the user's browser.
// So the user could connect to the actually running handler.
res.statusCode = 302
res.setHeader('Location', req.url)
res.end('302')
} else if (reloading) {
// Webpack config is reloading. So, we need to wait until it's done and
// reload user's browser.
// So the user could connect to the new handler and webpack setup.
this.waitUntilReloaded()
.then(() => {
res.statusCode = 302
res.setHeader('Location', req.url)
res.end('302')
})
} else {
if (!/^\/_next\/on-demand-entries-ping/.test(req.url)) return next()
const { query } = parse(req.url, true)
const page = normalizePage(query.page)
const entryInfo = entries[page]
// If there's no entry.
// Then it seems like an weird issue.
if (!entryInfo) {
const message = `Client pings, but there's no entry for page: ${page}`
console.error(message)
sendJson(res, { invalid: true })
return
}
sendJson(res, { success: true })
// We don't need to maintain active state of anything other than BUILT entries
if (entryInfo.status !== BUILT) return
// If there's an entryInfo
lastAccessPages.pop()
lastAccessPages.unshift(page)
entryInfo.lastActiveTime = Date.now()
}
}
}
}
}
function addEntry (compilation, context, name, entry) {
return new Promise((resolve, reject) => {
const dep = DynamicEntryPlugin.createDependency(entry, name)
compilation.addEntry(context, dep, name, (err) => {
if (err) return reject(err)
resolve()
})
})
}
function disposeInactiveEntries (devMiddleware, entries, lastAccessPages, maxInactiveAge) {
const disposingPages = []
Object.keys(entries).forEach((page) => {
const { lastActiveTime, status } = entries[page]
// This means this entry is currently building or just added
// We don't need to dispose those entries.
if (status !== BUILT) return
// We should not build the last accessed page even we didn't get any pings
// Sometimes, it's possible our XHR ping to wait before completing other requests.
// In that case, we should not dispose the current viewing page
if (lastAccessPages[0] === page) return
if (Date.now() - lastActiveTime > maxInactiveAge) {
disposingPages.push(page)
}
})
if (disposingPages.length > 0) {
disposingPages.forEach((page) => {
delete entries[page]
})
console.log(`> Disposing inactive page(s): ${disposingPages.join(', ')}`)
devMiddleware.invalidate()
}
}
// /index and / is the same. So, we need to identify both pages as the same.
// This also applies to sub pages as well.
function normalizePage (page) {
return page.replace(/\/index$/, '/')
}
function sendJson (res, payload) {
res.setHeader('Content-Type', 'application/json')
res.status = 200
res.end(JSON.stringify(payload))
}
// Make sure only one invalidation happens at a time
// Otherwise, webpack hash gets changed and it'll force the client to reload.
class Invalidator {
constructor (devMiddleware) {
this.devMiddleware = devMiddleware
this.building = false
this.rebuildAgain = false
}
invalidate () {
// If there's a current build is processing, we won't abort it by invalidating.
// (If aborted, it'll cause a client side hard reload)
// But let it to invalidate just after the completion.
// So, it can re-build the queued pages at once.
if (this.building) {
this.rebuildAgain = true
return
}
this.building = true
this.devMiddleware.invalidate()
}
startBuilding () {
this.building = true
}
doneBuilding () {
this.building = false
if (this.rebuildAgain) {
this.rebuildAgain = false
this.invalidate()
}
}
}