White space is always condensed for non-pre HTML tags, which can be a semantic change

[CodingMarkus]

Currently white space is condensed in HTML text nodes, unless those belong to a pre tag.

The problem with that heuristic is that using CSS, every tag can act like a pre tag (white-space: pre, or white-space: pre-wrap).

[CodingMarkus]

I don’t think this can be solved automatically. It could be solved if the CSS code were embedded in the HTML code, but that doesn’t have to be the case. Also, to really solve it, you would need a full DOM tree parser, since CSS rules don’t only apply to simple tags, IDs, or classes. They can also be rather complex, such as selecting the third element of type X with class Y after element Z. To find those elements, you need a full CSS rule parser and a full DOM tree to apply the rules to.

The only safe approach would be to never condense spaces in text nodes by default. Instead, only do so if the user tells cminify, via an option, that it is safe to condense spaces for all non-pre elements and unsafe to do so for pre elements.

Also keep in mind: CSS can also make pre behave just like p, in which case condensing spaces would be okay.

So the option would still only enable a default heuristic or it would disable a default heuristic but I think options should rather enable risky behavior and not risky behavior should be enabled by default and options should be used to disable it.