Description
Describe the bug
Svelte 4 could be used on XHTML documents. With Svelte 5, this seems to be no longer the case.
One issue is that <!> is used as a hydration marker in Svelte 5.
HTML fragments containing this marker can then be passed to create_fragment_from_html in reconciler.js:
export function create_fragment_from_html(html) {
var elem = document.createElement('template');
elem.innerHTML = html;
return elem.content;
}
This then fails when trying to assign the HTML fragment to the element.innerHTML with the error message that the fragment is not valid XML.
The only workaround I found was post-processing the generated JS file and replacing instances of <!> with <!---->. With this replacement, the code seems to work. However, having to post-process the generated JS file using string operations is a really bad hack.
I believe Svelte code should not use <!> but rather <!----> to be compatible with XHTML/XML environments in the same way that Svelte 4 was.
Reproduction
I don't think my report is vague.
Logs
System Info
System:
OS: macOS 14.7.4
CPU: (8) arm64 Apple M2
Memory: 134.42 MB / 24.00 GB
Shell: 5.9 - /bin/zsh
Binaries:
Node: 18.18.0 - ~/.nvm/versions/node/v18.18.0/bin/node
Yarn: 1.22.19 - ~/.nvm/versions/node/v18.18.0/bin/yarn
npm: 9.8.1 - ~/.nvm/versions/node/v18.18.0/bin/npm
Browsers:
Chrome: 135.0.7049.96
npmPackages:
svelte: ^5.25.12 => 5.27.1Severity
blocking an upgrade