chore: 优先从环境变量读取 manifest 路径

packages/preset-umi/templates/server.tpl

@@ -5,6 +5,8 @@ import { createHistory as createClientHistory } from './core/history';
 import { ServerInsertedHTMLContext } from './core/serverInsertedHTMLContext';
 import { createPluginManager } from './core/plugin';
 import createRequestHandler, { createMarkupGenerator, createUmiHandler, createUmiServerLoader, createAppRootElement } from '{{{ umiServerPath }}}';
+import fs from 'fs';
+import path from 'path';
 {{{ imports }}}
 {{{ entryCodeAhead }}}
 let helmetContext;
@@ -20,8 +22,17 @@ const routesWithServerLoader = {
 };
 
 export function getManifest(sourceDir) {
-  return JSON.parse(require('fs').readFileSync(
-  sourceDir ? require('path').join(sourceDir,'build-manifest.json') : '{{{ assetsPath }}}', 'utf-8'));
+  let manifestPath;
+  if (process.env.SSR_RESOURCE_DIR) {
+    manifestPath = path.join(process.env.SSR_RESOURCE_DIR,'build-manifest.json')
+  } else if (sourceDir) {
+    manifestPath = path.join(sourceDir,'build-manifest.json')
+  }
+   else {
+    manifestPath = '{{{ assetsPath }}}'
+   }
+
+   return JSON.parse(fs.readFileSync(manifestPath), 'utf-8');
 }
 
 export function createHistory(opts) {