Fix support of CSS nesting (Non-transparent backgrounds on some sites were not saved correctly)

[tglsf]

Describe the bug
Non-transparent backgrounds on some sites were not saved correctly. The screenshot shows the top bar and semi-transparent backgrounds missing, despite enabling hidden elements and scripts in the configuration.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'http://symphonysounds.net/ssreq3/'
2. Try enabling and disabling the retention of hidden elements and scripts.
3. Save them.
4. Check the result.

Screenshots
The top is the original website, and the bottom is the saved page (as seen in the URL bar).

Environment

• OS: Windows 10 24H2
• Browser: Firefox
• Version: 134.0.2 (64 bits)

[gildas-lormeau]

Thank you for the detailed report. I confirm I was able to reproduce the issue. This is due to a technical limitation when trying to optimize the stylesheets. I should be able to fix it though. Meanwhile, you can circumvent the issue by disabling the option "Stylesheets > remove unused styles".

[tglsf]

Thank you for the detailed report. I confirm I was able to reproduce the issue. This is due to a technical limitation when trying to optimize the stylesheets. I should be able to fix it though. Meanwhile, you can circumvent the issue by disabling the option "Stylesheets > remove unused styles".

Thanks for your reply. I unchecked that option, but the issue remains:

1. Some white backgrounds are missing. (See the screenshot: the top shows the original page, the bottom shows the saved page.)
2. Before saving, I unchecked "Block Scripts" in Options -> Network. Opening the saved page makes Firefox use over 20GB of memory, crashing Windows 11.

Screenshots:

[gildas-lormeau]

@tglsf Thank you for the feedback. I confirm the issue. I did not notice the missing white background. For the record, this bug is related to this feature which is quite recent: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_selectors/Selectors_and_combinators#creating_complex_selectors_with_css_nesting

[gildas-lormeau]

For the record, this issue is related to csstree/csstree#268.

It can be reproduced by running the code below which returns body{> section #release {... instead of body{> section#release {... (cf. space between section and #release).

csstree.generate(csstree.parse(`
  body {
    > section#release {
      .release-box { }
    }
  }
`));