Ensure correct key order (#6616)

* Ensure correct key order

* Fix bug

* Format this document while we're at it

packages/next/build/webpack/plugins/build-manifest-plugin.js

 import { RawSource } from 'webpack-sources'
-import { BUILD_MANIFEST, ROUTE_NAME_REGEX, IS_BUNDLED_PAGE_REGEX, CLIENT_STATIC_FILES_RUNTIME_MAIN } from 'next-server/constants'
+import {
+  BUILD_MANIFEST,
+  ROUTE_NAME_REGEX,
+  IS_BUNDLED_PAGE_REGEX,
+  CLIENT_STATIC_FILES_RUNTIME_MAIN
+} from 'next-server/constants'
 
 // This plugin creates a build-manifest.json for all assets that are being output
 // It has a mapping of "entry" filename to real filename. Because the real filename can be hashed in production
 export default class BuildManifestPlugin {
   apply (compiler) {
-    compiler.hooks.emit.tapAsync('NextJsBuildManifest', (compilation, callback) => {
-      const { chunks } = compilation
-      const assetMap = { devFiles: [], pages: {} }
+    compiler.hooks.emit.tapAsync(
+      'NextJsBuildManifest',
+      (compilation, callback) => {
+        const { chunks } = compilation
+        const assetMap = { devFiles: [], pages: {} }
 
-      const mainJsChunk = chunks.find((c) => c.name === CLIENT_STATIC_FILES_RUNTIME_MAIN)
-      const mainJsFiles = mainJsChunk && mainJsChunk.files.length > 0 ? mainJsChunk.files.filter((file) => /\.js$/.test(file)) : []
+        const mainJsChunk = chunks.find(
+          c => c.name === CLIENT_STATIC_FILES_RUNTIME_MAIN
+        )
+        const mainJsFiles =
+          mainJsChunk && mainJsChunk.files.length > 0
+            ? mainJsChunk.files.filter(file => /\.js$/.test(file))
+            : []
 
-      for (const filePath of Object.keys(compilation.assets)) {
-        const path = filePath.replace(/\\/g, '/')
-        if (/^static\/development\/dll\//.test(path)) {
-          assetMap.devFiles.push(path)
-        }
-      }
-
-      // compilation.entrypoints is a Map object, so iterating over it 0 is the key and 1 is the value
-      for (const [, entrypoint] of compilation.entrypoints.entries()) {
-        const result = ROUTE_NAME_REGEX.exec(entrypoint.name)
-        if (!result) {
-          continue
+        for (const filePath of Object.keys(compilation.assets)) {
+          const path = filePath.replace(/\\/g, '/')
+          if (/^static\/development\/dll\//.test(path)) {
+            assetMap.devFiles.push(path)
+          }
         }
 
-        const pagePath = result[1]
+        // compilation.entrypoints is a Map object, so iterating over it 0 is the key and 1 is the value
+        for (const [, entrypoint] of compilation.entrypoints.entries()) {
+          const result = ROUTE_NAME_REGEX.exec(entrypoint.name)
+          if (!result) {
+            continue
+          }
 
-        if (!pagePath) {
-          continue
-        }
+          const pagePath = result[1]
 
-        const filesForEntry = []
-        for (const chunk of entrypoint.chunks) {
-          // If there's no name or no files
-          if (!chunk.name || !chunk.files) {
+          if (!pagePath) {
             continue
           }
 
-          for (const file of chunk.files) {
-            if (/\.map$/.test(file) || /\.hot-update\.js$/.test(file)) {
+          const filesForEntry = []
+          for (const chunk of entrypoint.chunks) {
+            // If there's no name or no files
+            if (!chunk.name || !chunk.files) {
               continue
             }
 
-            // Only `.js` and `.css` files are added for now. In the future we can also handle other file types.
-            if (!/\.js$/.test(file) && !/\.css$/.test(file)) {
-              continue
-            }
+            for (const file of chunk.files) {
+              if (/\.map$/.test(file) || /\.hot-update\.js$/.test(file)) {
+                continue
+              }
 
-            // The page bundles are manually added to _document.js as they need extra properties
-            if (IS_BUNDLED_PAGE_REGEX.exec(file)) {
-              continue
-            }
+              // Only `.js` and `.css` files are added for now. In the future we can also handle other file types.
+              if (!/\.js$/.test(file) && !/\.css$/.test(file)) {
+                continue
+              }
+
+              // The page bundles are manually added to _document.js as they need extra properties
+              if (IS_BUNDLED_PAGE_REGEX.exec(file)) {
+                continue
+              }
 
-            filesForEntry.push(file.replace(/\\/g, '/'))
+              filesForEntry.push(file.replace(/\\/g, '/'))
+            }
           }
-        }
 
-        assetMap.pages[`/${pagePath.replace(/\\/g, '/')}`] = [...filesForEntry, ...mainJsFiles]
-      }
+          assetMap.pages[`/${pagePath.replace(/\\/g, '/')}`] = [
+            ...filesForEntry,
+            ...mainJsFiles
+          ]
+        }
 
-      if (typeof assetMap.pages['/index'] !== 'undefined') {
-        assetMap.pages['/'] = assetMap.pages['/index']
-      }
+        if (typeof assetMap.pages['/index'] !== 'undefined') {
+          assetMap.pages['/'] = assetMap.pages['/index']
+        }
 
-      assetMap.pages = Object.keys(assetMap.pages)
-        .sort()
-        .reduce((a, c) => Object.assign(a, { [c]: assetMap.pages[c] }), {})
+        assetMap.pages = Object.keys(assetMap.pages)
+          .sort()
+          // eslint-disable-next-line
+          .reduce((a, c) => ((a[c] = assetMap.pages[c]), a), {})
 
-      compilation.assets[BUILD_MANIFEST] = new RawSource(JSON.stringify(assetMap, null, 2))
-      callback()
-    })
+        compilation.assets[BUILD_MANIFEST] = new RawSource(
+          JSON.stringify(assetMap, null, 2)
+        )
+        callback()
+      }
+    )
   }
 }