Failed parsing 'srcset' attribute value since it has an unknown descriptor

[alizhdanov]

Version

13.5.0

Reproduction link

https://github.com/makedonec88/vue-loader-srcset-bug

Steps to reproduce

If you haven't specified srcset descriptor vue'll render it with undefined and in my case, break picture tag behaviour

<picture>
  <source srcset="http://www.gstatic.com/webp/gallery/1.webp">
  <source srcset="http://www.gstatic.com/webp/gallery/1.jpg">
  <img src="http://www.gstatic.com/webp/gallery/1.jpg" alt="test image">
</picture>

What is expected?

The same <picture> tag

What is actually happening?

<picture>
  <source srcset="http://www.gstatic.com/webp/gallery/1.webp undefined">
  <source srcset="http://www.gstatic.com/webp/gallery/1.jpg undefined">
  <img src="http://www.gstatic.com/webp/gallery/1.jpg" alt="test image">
</picture>

---

Specs say

srcset value must consist of one or more image candidate strings ...
... An image candidate string consists of ...
...Zero or one of the following: A width descriptor or A pixel density descriptor

Si I'm expecting that I don't have to specify descriptor in each srcset

P.S. I believe related to this issue #1005