fix(scanner): respect experimentalDecorators: true

packages/vite/src/node/optimizer/scan.ts

@@ -37,6 +37,7 @@ import {
 import type { PluginContainer } from '../server/pluginContainer'
 import { createPluginContainer } from '../server/pluginContainer'
 import { transformGlobImport } from '../plugins/importMetaGlob'
+import { loadTsconfigJsonForFile } from '../plugins/esbuild'
 
 type ResolveIdOptions = Parameters<PluginContainer['resolveId']>[2]
 
@@ -216,6 +217,21 @@ async function prepareEsbuildScanner(
   const { plugins = [], ...esbuildOptions } =
     config.optimizeDeps?.esbuildOptions ?? {}
 
+  // The plugin pipeline automatically loads the closest tsconfig.json.
+  // But esbuild doesn't support reading tsconfig.json if the plugin has resolved the path (https://github.com/evanw/esbuild/issues/2265).
+  // Due to syntax incompatibilities between the experimental decorators in TypeScript and TC39 decorators,
+  // we cannot simply set `"experimentalDecorators": true` or `false`. (https://github.com/vitejs/vite/pull/15206#discussion_r1417414715)
+  // Therefore, we use the closest tsconfig.json from the root to make it work in most cases.
+  let tsconfigRaw = esbuildOptions.tsconfigRaw
+  if (!tsconfigRaw && !esbuildOptions.tsconfig) {
+    const tsconfigResult = await loadTsconfigJsonForFile(
+      path.join(config.root, '_dummy.js'),
+    )
+    if (tsconfigResult.compilerOptions?.experimentalDecorators) {
+      tsconfigRaw = { compilerOptions: { experimentalDecorators: true } }
+    }
+  }
+
   return await esbuild.context({
     absWorkingDir: process.cwd(),
     write: false,
@@ -228,6 +244,7 @@ async function prepareEsbuildScanner(
     logLevel: 'silent',
     plugins: [...plugins, plugin],
     ...esbuildOptions,
+    tsconfigRaw,
   })
 }
 

packages/vite/src/node/plugins/esbuild.ts

@@ -440,7 +440,7 @@ function prettifyMessage(m: Message, code: string): string {
 
 let tsconfckCache: TSConfckCache<TSConfckParseResult> | undefined
 
-async function loadTsconfigJsonForFile(
+export async function loadTsconfigJsonForFile(
   filename: string,
 ): Promise<TSConfigJSON> {
   try {

playground/tsconfig-json/__tests__/tsconfig-json.spec.ts

@@ -2,7 +2,7 @@ import path from 'node:path'
 import fs from 'node:fs'
 import { transformWithEsbuild } from 'vite'
 import { describe, expect, test } from 'vitest'
-import { browserLogs } from '~utils'
+import { browserLogs, isServe, serverLogs } from '~utils'
 
 test('should respected each `tsconfig.json`s compilerOptions', () => {
   // main side effect should be called (because of `"importsNotUsedAsValues": "preserve"`)
@@ -21,6 +21,16 @@ test('should respected each `tsconfig.json`s compilerOptions', () => {
   expect(browserLogs).toContain('data setter in NestedWithExtendsBase')
 })
 
+test.runIf(isServe)('scanner should not error with decorators', () => {
+  expect(serverLogs).not.toStrictEqual(
+    expect.arrayContaining([
+      expect.stringContaining(
+        'Parameter decorators only work when experimental decorators are enabled',
+      ),
+    ]),
+  )
+})
+
 describe('transformWithEsbuild', () => {
   test('merge tsconfigRaw object', async () => {
     const main = path.resolve(__dirname, '../src/main.ts')

playground/tsconfig-json/src/decorator.ts

@@ -1,11 +1,11 @@
+// @ts-nocheck playground/tsconfig.json does not have decorators enabled
 function first() {
   return function (...args: any[]) {}
 }
 
 export class Foo {
   @first()
-  // @ts-expect-error we intentionally not enable `experimentalDecorators` to test esbuild compat
-  method(@first test: string) {
+  method(@first() test: string) {
     return test
   }
 }