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HTML Purifier: Removing an element conditionally based on its attributes

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南笙
南笙 2020-12-03 23:46

As per the HTML Purifier smoketest, \'malformed\' URIs are occasionally discarded to leave behind an attribute-less anchor tag, e.g.

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  • 终归单人心
    2020-12-04 00:23

    Success! Thanks to Ambush Commander and mcgrailm in another question, I am now using a hilariously simple solution:

    // a bit of context
$htmlDef = $this->configuration->getHTMLDefinition(true);
$anchor  = $htmlDef->addBlankElement('a');

// HTMLPurifier_AttrTransform_RemoveLoneHttp strips 'href="http:/"' from
// all anchor tags (see first post for class detail)
$anchor->attr_transform_post[] = new HTMLPurifier_AttrTransform_RemoveLoneHttp();

// this is the magic! We're making 'href' a required attribute (note the
// asterisk) - now HTML Purifier removes <a></a>, as well as
// <a href="http:/"></a> after HTMLPurifier_AttrTransform_RemoveLoneHttp
// is through with it!
$htmlDef->addAttribute('a', 'href*', new HTMLPurifier_AttrDef_URI());

    It works, it works, bahahahaHAHAHAHAnhͥͤͫ̀ğͮ͑̆ͦó̓̉ͬ͋h́ͧ̆̈́̉ğ̈́͐̈a̾̈́̑ͨô̔̄̑̇g̀̄h̘̝͊̐ͩͥ̋ͤ͛g̦̣̙̙̒̀ͥ̐̔ͅo̤̣hg͓̈́͋̇̓́̆a͖̩̯̥͕͂̈̐ͮ̒o̶ͬ̽̀̍ͮ̾ͮ͢҉̩͉̘͓̙̦̩̹͍̹̠̕g̵̡͔̙͉̱̠̙̩͚͑ͥ̎̓͛̋͗̍̽͋͑̈́̚...! * manic laughter, gurgling noises, keels over with a smile on her face *

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  • 清酒与你
    2020-12-04 00:29

    The fact that you can't remove elements with a TagTransform appears to have been an implementation detail. The classic mechanism for removing nodes (a smidge higher-level than just tags) is to use an Injector though.

    Anyway, the particular piece of functionality you're looking for is already implemented as %AutoFormat.RemoveEmpty

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  • 野性不改
    2020-12-04 00:31

    For perusal, this is my current solution. It works, but bypasses HTML Purifier entirely.

    /**
 * Removes <a></a> and <a href="http:/"></a> tags from the purified
 * HTML.
 * @todo solve this with an injector?
 * @param string $purified The purified HTML
 * @return string The purified HTML, sans pointless anchors.
 */
private function anchorCull($purified)
{
    if (empty($purified)) return '';
    // re-parse HTML
    $domTree = new DOMDocument();
    $domTree->loadHTML($purified);
    // find all anchors (even good ones)
    $anchors = $domTree->getElementsByTagName('a');
    // collect bad anchors (destroying them in this loop breaks the DOM)
    $destroyNodes = array();
    for ($i = 0; ($i < $anchors->length); $i++) {
        $anchor = $anchors->item($i);
        $href   = $anchor->attributes->getNamedItem('href');
        // <a></a>
        if (is_null($href)) {
            $destroyNodes[] = $anchor;
        // <a href="http:/"></a>
        } else if ($href->nodeValue == 'http:/') {
            $destroyNodes[] = $anchor;
        }
    }
    // destroy the collected nodes
    foreach ($destroyNodes as $node) {
        // preserve content
        $retain = $node->childNodes;
        for ($i = 0; ($i < $retain->length); $i++) {
            $rnode = $retain->item($i);
            $node->parentNode->insertBefore($rnode, $node);
        }
        // actually destroy the node
        $node->parentNode->removeChild($node);
    }
    // strip out HTML out of DOM structure string
    $html = $domTree->saveHTML();
    $begin = strpos($html, '<body>') + strlen('<body>');
    $end   = strpos($html, '</body>');
    return substr($html, $begin, $end - $begin);
}

    I'd still much rather have a good HTML Purifier solution to this, so, just as a heads-up, this answer won't end up self-accepted. But in case no better answer ends up coming around, at least it might help those with similar issues. :)

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