Removing width attribute on an image with a caption removes entire caption

[catchmyfame]

If you insert an image with a caption into the visual editor, it will create code like:

[caption id="attachment_12345" align="alignnone" width="150"]<img class="wp-image-12345 size-thumbnail" src="https://www.example.com/wp-content/uploads/2017/03/image.png" alt="" width="150" height="150" /> My caption[/caption]

If you switch from the visual editor to the text editor and remove the width attribute of the image to get:

[caption id="attachment_12345" align="alignnone" width="150"]<img class="wp-image-12345 size-thumbnail" src="https://www.example.com/wp-content/uploads/2017/03/image.png" alt="" height="150" /> My caption[/caption]

And then either update the post, or switch back to the visual editor, the caption is stripped and only the image remains:

<img class="wp-image-12345 size-thumbnail" src="https://www.example.com/wp-content/uploads/2017/03/image.png" alt="" height="150" />

Removing the height attribute doesn't appear to cause the same behavior. I don't believe that removing the width attribute on the image should result in both the caption being stripped and the [caption] shortcode being removed.

I'm not sure but this might be related to [27426] and #23103.

[antpb]

In the recent Media component meeting we reviewed this issue and confirmed that the issue exists with the classic-editor plugin enabled but not in the classic-block available in Gutenberg. This is still valid for Classic Editor so we should leave this as future release and this will need a patch. :)