fix(lib): keep annotation comments for es output (#337)

Author: sapphi-red

packages/vite/src/node/build.ts

@@ -789,7 +789,15 @@ async function buildEnvironment(
             (typeof input === 'string' || Object.keys(input).length === 1)),
         minify:
           options.minify === 'oxc'
-            ? true
+            ? libOptions && (format === 'es' || format === 'esm')
+              ? {
+                  compress: true,
+                  mangle: true,
+                  // Do not minify whitespace for ES lib output since that would remove
+                  // pure annotations and break tree-shaking
+                  removeWhitespace: false,
+                }
+              : true
             : options.minify === false
               ? 'dce-only'
               : false,

playground/lib/__tests__/lib.spec.ts

@@ -53,14 +53,16 @@ describe.runIf(isBuild)('build', () => {
     expect(code).not.toMatch('__vitePreload')
 
     // Test that library chunks are hashed
-    expect(code).toMatch(/await import\(`\.\/message-[-\w]{8}.js`\)/)
+    expect(code).toMatch(/await import\("\.\/message-[-\w]{8}.js"\)/)
   })
 
   test('Library mode does not have any reference to pure CSS chunks', async () => {
     const code = readFile('dist/lib/dynamic-import-message.es.mjs')
 
     // Does not import pure CSS chunks and replaced by `Promise.resolve({})` instead
-    expect(code).not.toMatch(/await import\(`\.\/dynamic-[-\w]{8}.js`\)/)
+    expect(code).not.toMatch(
+      /await import\(['"`]\.\/dynamic-[-\w]{8}.js['"`]\)/,
+    )
     expect(code).toMatch(/await Promise.resolve\(\{.*\}\)/)
   })