fix(css): lightningcss minify failed when build.target: 'es6' (#21933)

Author: ilharp

packages/vite/src/node/__tests__/plugins/css.spec.ts

@@ -274,6 +274,10 @@ describe('convertTargets', () => {
       safari: 852224,
     })
   })
+
+  test('supports es6 as an alias of es2015', () => {
+    expect(convertTargets('es6')).toStrictEqual(convertTargets('es2015'))
+  })
 })
 
 describe('getEmptyChunkReplacer', () => {

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

@@ -3479,7 +3479,7 @@ const esMap: Record<number, string[]> = {
   ],
 }
 
-const esRE = /es(\d{4})/
+const esRE = /es(6|\d{4})/
 const versionRE = /\d/
 
 const convertTargetsCache = new Map<
@@ -3497,7 +3497,7 @@ export const convertTargets = (
   const entriesWithoutES = arraify(esbuildTarget).flatMap((e) => {
     const match = esRE.exec(e)
     if (!match) return e
-    const year = Number(match[1])
+    const year = match[1] === '6' ? 2015 : Number(match[1])
     if (!esMap[year]) throw new Error(`Unsupported target "${e}"`)
     return esMap[year]
   })