feat: add experimental option to skip SSR transform

packages/vite/src/node/config.ts

@@ -292,6 +292,14 @@ export interface ExperimentalOptions {
    * @default false
    */
   hmrPartialAccept?: boolean
+  /**
+   * Skips SSR transform to make it easier to use Vite with Node ESM loaders.
+   * @warning Enabling this will break normal operation of Vite's SSR in development mode.
+   *
+   * @experimental
+   * @default false
+   */
+  skipSsrTransform?: boolean
 }
 
 export interface LegacyOptions {
@@ -462,13 +470,18 @@ export async function resolveConfig(
   )
 
   const clientAlias = [
-    { find: /^\/?@vite\/env/, replacement: ENV_ENTRY },
-    { find: /^\/?@vite\/client/, replacement: CLIENT_ENTRY },
+    { find: /^\/?@vite\/env/, replacement: () => ENV_ENTRY },
+    { find: /^\/?@vite\/client/, replacement: () => CLIENT_ENTRY },
   ]
 
   // resolve alias with internal client alias
   const resolvedAlias = normalizeAlias(
-    mergeAlias(clientAlias, config.resolve?.alias || []),
+    mergeAlias(
+      // @ts-expect-error because @rollup/plugin-alias' type doesn't allow function
+      // replacement, but its implementation does work with function values.
+      clientAlias,
+      config.resolve?.alias || [],
+    ),
   )
 
   const resolveOptions: ResolvedConfig['resolve'] = {

packages/vite/src/node/server/transformRequest.ts

@@ -266,13 +266,14 @@ async function loadAndTransform(
     }
   }
 
-  const result = ssr
-    ? await server.ssrTransform(code, map as SourceMap, url, originalCode)
-    : ({
-        code,
-        map,
-        etag: getEtag(code, { weak: true }),
-      } as TransformResult)
+  const result =
+    ssr && !server.config.experimental.skipSsrTransform
+      ? await server.ssrTransform(code, map as SourceMap, url, originalCode)
+      : ({
+          code,
+          map,
+          etag: getEtag(code, { weak: true }),
+        } as TransformResult)
 
   // Only cache the result if the module wasn't invalidated while it was
   // being processed, so it is re-processed next time if it is stale