Hot reload error page (#190)

* add detach-plugin

* detach-plugin: remove unused property

* watch-pages-plugin: replace _error.js when user defined one was added/removed

* dynamic-entry-plugin: delete cache

* fix HMR settings for _error.js

* render: pass error only on dev

* hot-reload: enable to hot-reload error page

* server: check if /_error has compilation errors

* webapck-dev-client: fix reloading /_error

client/webpack-dev-client/index.js

@@ -107,6 +107,18 @@ const onSocketMsg = {
     }
   },
   reload (route) {
+    if (route === '/_error') {
+      for (const r of Object.keys(next.router.components)) {
+        const { Component } = next.router.components[r]
+        if (Component.__route === '/_error-debug') {
+          // reload all '/_error-debug'
+          // which are expected to be errors of '/_error' routes
+          next.router.reload(r)
+        }
+      }
+      return
+    }
+
     next.router.reload(route)
   },
   close () {

server/build/loaders/hot-self-accept-loader.js

@@ -5,19 +5,34 @@ module.exports = function (content) {
 
   const route = getRoute(this)
 
-  return content + `
+  return `${content}
     if (module.hot) {
       module.hot.accept()
+
+      var Component = module.exports.default || module.exports
+      Component.__route = ${JSON.stringify(route)}
+
       if (module.hot.status() !== 'idle') {
-        var Component = module.exports.default || module.exports
-        next.router.update('${route}', Component)
+        var components = next.router.components
+        for (var r in components) {
+          if (!components.hasOwnProperty(r)) continue
+
+          if (components[r].Component.__route === ${JSON.stringify(route)}) {
+            next.router.update(r, Component)
+          }
+        }
       }
     }
   `
 }
 
+const nextPagesDir = resolve(__dirname, '..', '..', '..', 'pages')
+
 function getRoute (loaderContext) {
   const pagesDir = resolve(loaderContext.options.context, 'pages')
-  const path = loaderContext.resourcePath
-  return '/' + relative(pagesDir, path).replace(/((^|\/)index)?\.js$/, '')
+  const { resourcePath } = loaderContext
+  const dir = [pagesDir, nextPagesDir]
+  .find((d) => resourcePath.indexOf(d) === 0)
+  const path = relative(dir, resourcePath)
+  return '/' + path.replace(/((^|\/)index)?\.js$/, '')
 }

server/build/plugins/detach-plugin.js

@@ -0,0 +1,73 @@
+
+export default class DetachPlugin {
+  apply (compiler) {
+    compiler.pluginDetachFns = new Map()
+    compiler.plugin = plugin(compiler.plugin)
+    compiler.apply = apply
+    compiler.detach = detach
+    compiler.getDetachablePlugins = getDetachablePlugins
+  }
+}
+
+export function detachable (Plugin) {
+  const { apply } = Plugin.prototype
+
+  Plugin.prototype.apply = function (compiler) {
+    const fns = []
+
+    const { plugin } = compiler
+    compiler.plugin = function (name, fn) {
+      fns.push(plugin.call(this, name, fn))
+    }
+
+    // collect the result of `plugin` call in `apply`
+    apply.call(this, compiler)
+
+    compiler.plugin = plugin
+
+    return fns
+  }
+}
+
+function plugin (original) {
+  return function (name, fn) {
+    original.call(this, name, fn)
+
+    return () => {
+      const names = Array.isArray(name) ? name : [name]
+      for (const n of names) {
+        const plugins = this._plugins[n] || []
+        const i = plugins.indexOf(fn)
+        if (i >= 0) plugins.splice(i, 1)
+      }
+    }
+  }
+}
+
+function apply (...plugins) {
+  for (const p of plugins) {
+    const fn = p.apply(this)
+    if (!fn) continue
+
+    const fns = this.pluginDetachFns.get(p) || new Set()
+
+    const _fns = Array.isArray(fn) ? fn : [fn]
+    for (const f of _fns) fns.add(f)
+
+    this.pluginDetachFns.set(p, fns)
+  }
+}
+
+function detach (...plugins) {
+  for (const p of plugins) {
+    const fns = this.pluginDetachFns.get(p) || new Set()
+    for (const fn of fns) {
+      if (typeof fn === 'function') fn()
+    }
+    this.pluginDetachFns.delete(p)
+  }
+}
+
+function getDetachablePlugins () {
+  return new Set(this.pluginDetachFns.keys())
+}

server/build/plugins/dynamic-entry-plugin.js

@@ -1,5 +1,9 @@
 import SingleEntryPlugin from 'webpack/lib/SingleEntryPlugin'
 import MultiEntryPlugin from 'webpack/lib/MultiEntryPlugin'
+import { detachable } from './detach-plugin'
+
+detachable(SingleEntryPlugin)
+detachable(MultiEntryPlugin)
 
 export default class DynamicEntryPlugin {
   apply (compiler) {
@@ -8,8 +12,9 @@ export default class DynamicEntryPlugin {
     compiler.removeEntry = removeEntry
     compiler.hasEntry = hasEntry
 
-    compiler.plugin('compilation', (compilation) => {
-      compilation.addEntry = compilationAddEntry(compilation.addEntry)
+    compiler.plugin('emit', (compilation, callback) => {
+      compiler.cache = compilation.cache
+      callback()
     })
   }
 }
@@ -37,21 +42,27 @@ function addEntry (entry, name = 'main') {
 }
 
 function removeEntry (name = 'main') {
+  for (const p of this.getDetachablePlugins()) {
+    if (!(p instanceof SingleEntryPlugin || p instanceof MultiEntryPlugin)) continue
+    if (p.name !== name) continue
+
+    if (this.cache) {
+      for (const id of Object.keys(this.cache)) {
+        const m = this.cache[id]
+        if (m.name === name) {
+          // cache of `MultiModule` is based on `name`,
+          // so delete it here for the case
+          // a new entry is added with the same name later
+          delete this.cache[id]
+        }
+      }
+    }
+
+    this.detach(p)
+  }
   this.entryNames.delete(name)
 }
 
 function hasEntry (name = 'main') {
   return this.entryNames.has(name)
 }
-
-function compilationAddEntry (original) {
-  return function (context, entry, name, callback) {
-    if (!this.compiler.entryNames.has(name)) {
-      // skip removed entry
-      callback()
-      return
-    }
-
-    return original.call(this, context, entry, name, callback)
-  }
-}

server/build/plugins/watch-pages-plugin.js

@@ -3,6 +3,7 @@ import { resolve, relative, join, extname } from 'path'
 export default class WatchPagesPlugin {
   constructor (dir) {
     this.dir = resolve(dir, 'pages')
+    this.prevFileDependencies = null
   }
 
   apply (compiler) {
@@ -11,6 +12,8 @@ export default class WatchPagesPlugin {
       compilation.contextDependencies =
         compilation.contextDependencies.concat([this.dir])
 
+      this.prevFileDependencies = compilation.fileDependencies
+
       callback()
     })
 
@@ -18,12 +21,18 @@ export default class WatchPagesPlugin {
     const getEntryName = (f) => {
       return join('bundles', relative(compiler.options.context, f))
     }
+    const errorPageName = join('bundles', 'pages', '_error.js')
 
     compiler.plugin('watch-run', (watching, callback) => {
       Object.keys(compiler.fileTimestamps)
       .filter(isPageFile)
+      .filter((f) => this.prevFileDependencies.indexOf(f) < 0)
       .forEach((f) => {
         const name = getEntryName(f)
+        if (name === errorPageName) {
+          compiler.removeEntry(name)
+        }
+
         if (compiler.hasEntry(name)) return
 
         const entries = ['webpack/hot/dev-server', f]
@@ -35,6 +44,13 @@ export default class WatchPagesPlugin {
       .forEach((f) => {
         const name = getEntryName(f)
         compiler.removeEntry(name)
+
+        if (name === errorPageName) {
+          compiler.addEntry([
+            'webpack/hot/dev-server',
+            join(__dirname, '..', '..', '..', 'pages', '_error.js')
+          ], name)
+        }
       })
 
       callback()

server/build/webpack.js

@@ -6,6 +6,7 @@ import UnlinkFilePlugin from './plugins/unlink-file-plugin'
 import WatchPagesPlugin from './plugins/watch-pages-plugin'
 import WatchRemoveEventPlugin from './plugins/watch-remove-event-plugin'
 import DynamicEntryPlugin from './plugins/dynamic-entry-plugin'
+import DetachPlugin from './plugins/detach-plugin'
 
 export default async function createCompiler (dir, { hotReload = false } = {}) {
   dir = resolve(dir)
@@ -22,7 +23,9 @@ export default async function createCompiler (dir, { hotReload = false } = {}) {
 
   const errorEntry = join('bundles', 'pages', '_error.js')
   const defaultErrorPath = join(nextPagesDir, '_error.js')
-  if (!entry[errorEntry]) entry[errorEntry] = defaultErrorPath
+  if (!entry[errorEntry]) {
+    entry[errorEntry] = defaultEntries.concat([defaultErrorPath])
+  }
 
   const errorDebugEntry = join('bundles', 'pages', '_error-debug.js')
   const errorDebugPath = join(nextPagesDir, '_error-debug.js')
@@ -42,6 +45,7 @@ export default async function createCompiler (dir, { hotReload = false } = {}) {
     })
   ].concat(hotReload ? [
     new webpack.HotModuleReplacementPlugin(),
+    new DetachPlugin(),
     new DynamicEntryPlugin(),
     new UnlinkFilePlugin(),
     new WatchRemoveEventPlugin(),
@@ -70,7 +74,10 @@ export default async function createCompiler (dir, { hotReload = false } = {}) {
   .concat(hotReload ? [{
     test: /\.js$/,
     loader: 'hot-self-accept-loader',
-    include: join(dir, 'pages')
+    include: [
+      join(dir, 'pages'),
+      nextPagesDir
+    ]
   }] : [])
   .concat([{
     test: /\.js$/,

server/index.js

@@ -83,13 +83,19 @@ export default class Server {
       try {
         html = await render(req.url, ctx, opts)
       } catch (err) {
-        if (err.code === 'ENOENT') {
-          res.statusCode = 404
-        } else {
-          console.error(err)
+        const _err = this.getCompilationError('/_error')
+        if (_err) {
           res.statusCode = 500
+          html = await render('/_error-debug', { ...ctx, err: _err }, opts)
+        } else {
+          if (err.code === 'ENOENT') {
+            res.statusCode = 404
+          } else {
+            console.error(err)
+            res.statusCode = 500
+          }
+          html = await render('/_error', { ...ctx, err }, opts)
         }
-        html = await render('/_error', { ...ctx, err }, opts)
       }
     }
 
@@ -111,13 +117,20 @@ export default class Server {
       try {
         json = await renderJSON(req.url, opts)
       } catch (err) {
-        if (err.code === 'ENOENT') {
-          res.statusCode = 404
-        } else {
-          console.error(err)
+        const _err = this.getCompilationError('/_error.json')
+        if (_err) {
           res.statusCode = 500
+          json = await renderJSON('/_error-debug.json', opts)
+          json = { ...json, err: errorToJSON(_err) }
+        } else {
+          if (err.code === 'ENOENT') {
+            res.statusCode = 404
+          } else {
+            console.error(err)
+            res.statusCode = 500
+          }
+          json = await renderJSON('/_error.json', opts)
         }
-        json = await renderJSON('/_error.json', opts)
       }
     }
 
@@ -129,9 +142,19 @@ export default class Server {
 
   async render404 (req, res) {
     const { dir, dev } = this
+    const opts = { dir, dev }
+
+    let html
+
+    const err = this.getCompilationError('/_error')
+    if (err) {
+      res.statusCode = 500
+      html = await render('/_error-debug', { req, res, err }, opts)
+    } else {
+      res.statusCode = 404
+      html = await render('/_error', { req, res }, opts)
+    }
 
-    res.statusCode = 404
-    const html = await render('/_error', { req, res }, { dir, dev })
     sendHTML(res, html)
   }
 

server/render.js

@@ -44,7 +44,7 @@ export async function render (url, ctx = {}, {
       component,
       props,
       ids: ids,
-      err: ctx.err ? errorToJSON(ctx.err) : null
+      err: (ctx.err && dev) ? errorToJSON(ctx.err) : null
     },
     dev,
     staticMarkup,