fix: srcSet with optional descriptor (#15905)

Co-authored-by: patak <[email protected]>

Author: murad-khafizov

packages/vite/src/node/__tests__/utils.spec.ts

@@ -338,6 +338,13 @@ describe('processSrcSetSync', () => {
       'data:image/avif;base64,aA+/0= 400w, data:image/avif;base64,bB+/9= 800w'
     expect(processSrcSetSync(base64, ({ url }) => url)).toBe(base64)
   })
+
+  test('should not break a regular URL in srcSet', async () => {
+    const source = 'https://anydomain/image.jpg'
+    expect(
+      processSrcSetSync('https://anydomain/image.jpg', ({ url }) => url),
+    ).toBe(source)
+  })
 })
 
 describe('flattenId', () => {

packages/vite/src/node/utils.ts

@@ -767,7 +767,9 @@ interface ImageCandidate {
 const escapedSpaceCharacters = /( |\\t|\\n|\\f|\\r)+/g
 const imageSetUrlRE = /^(?:[\w\-]+\(.*?\)|'.*?'|".*?"|\S*)/
 function joinSrcset(ret: ImageCandidate[]) {
-  return ret.map(({ url, descriptor }) => `${url} ${descriptor}`).join(', ')
+  return ret
+    .map(({ url, descriptor }) => url + (descriptor ? ` ${descriptor}` : ''))
+    .join(', ')
 }
 
 function splitSrcSetDescriptor(srcs: string): ImageCandidate[] {