Automatic fix of an ID name causes loss of CSS styling

[quinta@ebf.cz]

When Calibre Editor's Check Book function reports an invalid ID, the automatic correction "Replace this id with a randomly generated valid id" (or "Try to automatically fix all fixable errors") changes the id attribute in the XHTML file, but does not update CSS selector referring to the ID.

As a result, the CSS rule no longer matches the element and its formatting is silently lost.

example:
xhtml:

<p id="_example">This paragraph is formatted by CSS.</p>

css:

#_example {
    text-align: right;
    font-weight: bold;
}

after autofix:
xhtml:

<p id="uiIKYKleNpAABQhFyzTceGC">This paragraph is formatted by CSS.</p>

css:
(without change)

expected behaviour:
css:

#uiIKYKleNpAABQhFyzTceGC {
    text-align: right;
    font-weight: bold;
}

Alternatively, if Calibre intentionally does not update CSS selectors, the automatic correction should warn that changing the ID may invalidate CSS rules referring to it.

(This appears to be a different issue from the historical bug concerning ID references in the OPF spine (Calibre bug 1479462).)

[quinta@ebf.cz]

Potential issue: A straightforward modification of the selector—based on changing a specific ID—could cause unwanted formatting change in (hypothetical) other XHTML document using the same CSS and containing an (hypothetical) ID of the same name...

Therefore, the solution would have to be more complex. And probably include analyzing occurrences of IDs with the same name and, if necessary, generating new CSS definitions (rather than modifying the selector in the existing one).

[kovidgoyal]

https://github.com/kovidgoyal/calibr...d838a29a1acfb8

[quinta@ebf.cz]

Originally Posted by quinta@ebf.cz

(...) Therefore, the solution would have to be more complex. And probably include analyzing occurrences of IDs with the same name and, if necessary, generating new CSS definitions (rather than modifying the selector in the existing one).

Or at least update all occurrences of an ID with the same name across all XHTML documents at once—like in the commit.

Thank you very much for lightning-fast response.