Can't find spec support for setting importRule.styleSheet.parentStyleSheet to null after deleting that import rule #13612
Description
Browsers seem to set importRule.styleSheet.parentStyleSheet to null after removing the rule via CSSOM.
Test case
<!DOCTYPE html>
<title>Remove a CSS rule: @import styleSheet unlinking</title>
<style>
@import url("data:text/css,.imported { color: red }");
.local { color: green }
</style>
<pre id="out"></pre>
<script>
const out = document.getElementById("out");
function log(msg) { out.textContent += msg + "\n"; }
// Wait for @import to load
setTimeout(() => {
const sheet = document.styleSheets[0];
const importRule = sheet.cssRules[0];
log("importRule.type = " + importRule.type + " (expecting 3 = IMPORT_RULE)");
log("importRule.styleSheet = " + importRule.styleSheet);
const importedSheet = importRule.styleSheet;
if (!importedSheet) {
log("(imported stylesheet not available, try opening via a local server)");
return;
}
log("");
log("=== Before deleteRule ===");
log("importedSheet.parentStyleSheet = " + importedSheet.parentStyleSheet);
log("importedSheet.ownerRule = " + importedSheet.ownerRule);
sheet.deleteRule(0);
log("");
log("=== After deleteRule ===");
log("importedSheet.parentStyleSheet = " + importedSheet.parentStyleSheet);
log("importedSheet.ownerRule = " + importedSheet.ownerRule);
}, 1000);
</script>However, the only place I can find that nulls out parent CSS style sheet is remove a CSS style sheet. And the only caller of that is some xsl-stylesheet thing.
In particular, remove a CSS rule does not call "remove a CSS style sheet" for @import rules. (It does null out the rule's parent CSS style sheet (something all CSS rules have), but not the rule's "associated CSS style sheet"'s parent CSS style sheet.)