fix(dev): strip utf-8 bom (#3162)

packages/playground/resolve/__tests__/resolve.spec.ts

@@ -1,5 +1,9 @@
 import { isBuild } from '../../testUtils'
 
+test('bom import', async () => {
+  expect(await page.textContent('.utf8-bom')).toMatch('[success]')
+})
+
 test('deep import', async () => {
   expect(await page.textContent('.deep-import')).toMatch('[2,4]')
 })

packages/playground/resolve/index.html

@@ -1,5 +1,8 @@
 <h1>Resolve</h1>
 
+<h2>Utf8-bom import</h2>
+<p class="utf8-bom">fail</p>
+
 <h2>Deep import</h2>
 <p>Should show [2,4]:<span class="pre deep-import">fail</span></p>
 
@@ -62,6 +65,10 @@ <h2>resolve.conditions</h2>
     document.querySelector(selector).textContent = text
   }
 
+  // import from a utf-8 bom file
+  import { msg as bomMsg } from './utf8-bom/main.js'
+  text('.utf8-bom', bomMsg)
+
   // deep import
   import slicedToArray from '@babel/runtime/helpers/esm/slicedToArray'
 

packages/playground/resolve/utf8-bom/main.js

@@ -0,0 +1,3 @@
+import '@babel/runtime/helpers/esm/slicedToArray'
+
+export const msg = '[success]'

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

@@ -112,6 +112,10 @@ export function importAnalysisPlugin(config: ResolvedConfig): Plugin {
       const rewriteStart = Date.now()
       await init
       let imports: readonly ImportSpecifier[] = []
+      // strip UTF-8 BOM
+      if (source.charCodeAt(0) === 0xfeff) {
+        source = source.slice(1)
+      }
       try {
         imports = parseImports(source)[0]
       } catch (e) {