add writeToDisk option to webpack plugin

packages/webpack-plugin/README.md

@@ -20,6 +20,24 @@ module.exports = {
 }
 ```
 
+## API
+
+### LoadablePlugin
+
+Create a webpack loadable plugin.
+
+| Arguments             | Description                                       |
+| --------------------- | ------------------------------------------------- |
+| `options`             | Optional options                                  |
+| `options.filename`    | Stats filename (default to `loadable-stats.json`) |
+| `options.writeToDisk` | Always write assets to disk (default to `false`)  |
+
+```js
+new LoadablePlugin({ filename: 'stats.json', writeToDisk: true })
+```
+
+> Writing file to disk can be useful if you are using `razzle` or `webpack-dev-server`.
+
 ## License
 
 MIT

packages/webpack-plugin/src/index.js

@@ -1,33 +1,113 @@
+const path = require('path')
+const fs = require('fs')
+
 class LoadablePlugin {
-  constructor({ filename = 'loadable-stats.json' } = {}) {
-    this.opts = { filename }
+  constructor({ filename = 'loadable-stats.json', writeToDisk = false } = {}) {
+    this.opts = { filename, writeToDisk }
+  }
+
+  handleEmit = (hookCompiler, callback) => {
+    const stats = hookCompiler.getStats().toJson({
+      hash: true,
+      publicPath: true,
+      assets: true,
+      chunks: false,
+      modules: false,
+      source: false,
+      errorDetails: false,
+      timings: false,
+    })
+    const result = JSON.stringify(stats, null, 2)
+
+    hookCompiler.assets[this.opts.filename] = {
+      source() {
+        return result
+      },
+      size() {
+        return result.length
+      },
+    }
+
+    if (this.opts.writeToDisk) {
+      this.writeAssetsFile(result)
+    }
+
+    callback()
+  }
+
+  /**
+   * Check if request is from Dev Server
+   * aka webpack-dev-server
+   * @method isRequestFromDevServer
+   * @returns {boolean} - True or False
+   */
+  isRequestFromDevServer = () => {
+    if (process.argv.some(arg => arg.includes('webpack-dev-server'))) {
+      return true
+    }
+    return (
+      this.compiler.outputFileSystem &&
+      this.compiler.outputFileSystem.constructor.name === 'MemoryFileSystem'
+    )
+  }
+
+  /**
+   * Get assets manifest output path
+   *
+   * @method getManifestOutputPath
+   * @returns {string} - Output path containing path + filename.
+   */
+  getManifestOutputPath = () => {
+    if (path.isAbsolute(this.opts.filename)) {
+      return this.opts.filename
+    }
+
+    if (this.isRequestFromDevServer() && this.compiler.options.devServer) {
+      let outputPath =
+        this.compiler.options.devServer.outputPath ||
+        this.compiler.outputPath ||
+        '/'
+
+      if (outputPath === '/') {
+        // eslint-disable-next-line no-console
+        console.warn(
+          'Please use an absolute path in options.output when using webpack-dev-server.',
+        )
+        outputPath = this.compiler.context || process.cwd()
+      }
+
+      return path.resolve(outputPath, this.opts.filename)
+    }
+
+    return path.resolve(this.compiler.outputPath, this.opts.filename)
+  }
+
+  /**
+   * Write Assets Manifest file
+   * @method writeAssetsFile
+   */
+  writeAssetsFile = manifest => {
+    const filePath = this.getManifestOutputPath()
+    const fileDir = path.dirname(filePath)
+
+    try {
+      if (!fs.existsSync(fileDir)) {
+        fs.mkdirSync(fileDir)
+      }
+    } catch (err) {
+      if (err.code !== 'EEXIST') {
+        throw err
+      }
+    }
+
+    fs.writeFileSync(filePath, manifest)
   }
 
   apply(compiler) {
     // Add a custom output.jsonpFunction: __LOADABLE_LOADED_CHUNKS__
     compiler.options.output.jsonpFunction = '__LOADABLE_LOADED_CHUNKS__'
 
-    compiler.hooks.emit.tap('@loadable/webpack-plugin', hookCompiler => {
-      const stats = hookCompiler.getStats().toJson({
-        hash: true,
-        publicPath: true,
-        assets: true,
-        chunks: false,
-        modules: false,
-        source: false,
-        errorDetails: false,
-        timings: false,
-      })
-      const result = JSON.stringify(stats, null, 2)
-      hookCompiler.assets[this.opts.filename] = {
-        source() {
-          return result
-        },
-        size() {
-          return result.length
-        },
-      }
-    })
+    compiler.hooks.emit.tapAsync('@loadable/webpack-plugin', this.handleEmit)
   }
 }