fix(ssr): load sourcemaps alongside modules (fix: #3288) (#11576)

packages/vite/src/node/ssr/ssrModuleLoader.ts

@@ -10,6 +10,7 @@ import {
 import { transformRequest } from '../server/transformRequest'
 import type { InternalResolveOptionsWithOverrideConditions } from '../plugins/resolve'
 import { tryNodeResolve } from '../plugins/resolve'
+import { genSourceMapUrl } from '../server/sourcemap'
 import {
   ssrDynamicImportKey,
   ssrExportAllKey,
@@ -25,6 +26,16 @@ interface SSRContext {
 
 type SSRModule = Record<string, any>
 
+// eslint-disable-next-line @typescript-eslint/no-empty-function
+const AsyncFunction = async function () {}.constructor as typeof Function
+let fnDeclarationLineCount = 0
+{
+  const body = '/*code*/'
+  const source = new AsyncFunction('a', 'b', body).toString()
+  fnDeclarationLineCount =
+    source.slice(0, source.indexOf(body)).split('\n').length - 1
+}
+
 const pendingModules = new Map<string, Promise<SSRModule>>()
 const pendingImports = new Map<string, string[]>()
 
@@ -181,17 +192,27 @@ async function instantiateModule(
     }
   }
 
+  let sourceMapSuffix = ''
+  if (result.map) {
+    const moduleSourceMap = Object.assign({}, result.map, {
+      // offset the first three lines of the module (function declaration and 'use strict')
+      mappings: ';'.repeat(fnDeclarationLineCount + 1) + result.map.mappings,
+    })
+    sourceMapSuffix =
+      '\n//# sourceMappingURL=' + genSourceMapUrl(moduleSourceMap)
+  }
+
   try {
-    // eslint-disable-next-line @typescript-eslint/no-empty-function
-    const AsyncFunction = async function () {}.constructor as typeof Function
     const initModule = new AsyncFunction(
       `global`,
       ssrModuleExportsKey,
       ssrImportMetaKey,
       ssrImportKey,
       ssrDynamicImportKey,
       ssrExportAllKey,
-      '"use strict";' + result.code + `\n//# sourceURL=${mod.url}`,
+      '"use strict";\n' +
+        result.code +
+        `\n//# sourceURL=${mod.url}${sourceMapSuffix}`,
     )
     await initModule(
       context.global,