Add dev runtime from web-starter

modules/server/AssetsUtils.js

@@ -0,0 +1,115 @@
+import fs from 'fs'
+import invariant from 'invariant'
+import webpack from 'webpack'
+
+const createAssets = (webpackStats) => {
+  const createURL = (asset) =>
+    webpackStats.publicPath + asset
+
+  const getAssets = (chunkName = 'main') => {
+    const assets = webpackStats.assetsByChunkName[chunkName] || []
+    return Array.isArray(assets) ? assets : [ assets ]
+  }
+
+  const getScriptURLs = (chunkName = 'main') =>
+    getAssets(chunkName)
+      .filter(asset => (/\.js$/).test(asset))
+      .map(createURL)
+
+  const getStyleURLs = (chunkName = 'main') =>
+    getAssets(chunkName)
+      .filter(asset => (/\.css$/).test(asset))
+      .map(createURL)
+
+  return {
+    createURL,
+    getAssets,
+    getScriptURLs,
+    getStyleURLs
+  }
+}
+
+/**
+ * An express middleware that sets req.assets from the build
+ * info in the given stats file. Should be used in production.
+ */
+export const staticAssets = (webpackStatsFile) => {
+  let stats
+  try {
+    stats = JSON.parse(fs.readFileSync(webpackStatsFile, 'utf8'))
+  } catch (error) {
+    invariant(
+      false,
+      'staticAssets middleware cannot read the build stats in %s; ' +
+      'do `npm run build` before starting the server',
+      webpackStatsFile
+    )
+  }
+
+  const assets = createAssets(stats)
+
+  return (req, res, next) => {
+    req.assets = assets
+    next()
+  }
+}
+
+/**
+ * An express middleware that sets req.assets from the
+ * latest result from a running webpack compiler (i.e. using
+ * webpack-dev-middleware). Should only be used in dev.
+ */
+export const assetsCompiler = (webpackCompiler) => {
+  let assets
+  webpackCompiler.plugin('done', (stats) => {
+    assets = createAssets(stats.toJson())
+  })
+
+  return (req, res, next) => {
+    invariant(
+      assets != null,
+      'assetsCompiler middleware needs a running compiler; ' +
+      'use webpack-dev-middleware in front of assetsCompiler'
+    )
+
+    req.assets = assets
+    next()
+  }
+}
+
+/**
+ * Creates a webpack compiler that automatically inlines the
+ * webpack dev runtime in all entry points.
+ */
+export const createDevCompiler = (webpackConfig, webpackRuntimeModuleID) =>
+  webpack({
+    ...webpackConfig,
+    entry: prependModuleID(
+      webpackConfig.entry,
+      webpackRuntimeModuleID
+    )
+  })
+
+/**
+ * Returns a modified copy of the given webpackEntry object with
+ * the moduleID in front of all other assets.
+ */
+const prependModuleID = (webpackEntry, moduleID) => {
+  if (typeof webpackEntry === 'string')
+    return [ moduleID, webpackEntry ]
+
+  if (Array.isArray(webpackEntry))
+    return [ moduleID, ...webpackEntry ]
+
+  if (webpackEntry && typeof webpackEntry === 'object') {
+    const entry = { ...webpackEntry }
+
+    for (const chunkName in entry)
+      if (entry.hasOwnProperty(chunkName))
+        entry[chunkName] = prependModuleID(entry[chunkName], moduleID)
+
+    return entry
+  }
+
+  throw new Error('Invalid webpack entry object')
+}