fix(removeUnknownsAndDefaults): skip if attr used in css selector (#2144)

Author: SethFalco

plugins/removeUnknownsAndDefaults.js

@@ -7,7 +7,11 @@ import {
 } from './_collections.js';
 import { detachNodeFromParent } from '../lib/xast.js';
 import { visitSkip } from '../lib/util/visit.js';
-import { collectStylesheet, computeStyle } from '../lib/style.js';
+import {
+  collectStylesheet,
+  computeStyle,
+  includesAttrSelector,
+} from '../lib/style.js';
 
 /**
  * @typedef RemoveUnknownsAndDefaultsParams
@@ -192,7 +196,12 @@ export const fn = (root, params) => {
             attributesDefaults.get(name) === value
           ) {
             // keep defaults if parent has own or inherited style
-            if (computedParentStyle?.[name] == null) {
+            if (
+              computedParentStyle?.[name] == null &&
+              !stylesheet.rules.some((rule) =>
+                includesAttrSelector(rule.selector, name),
+              )
+            ) {
               delete node.attributes[name];
             }
           }

test/plugins/removeUnknownsAndDefaults.17.svg.txt

@@ -0,0 +1,26 @@
+Don't remove unknown attributes or attributes with default values if that
+attribute is referenced in an attribute selector in CSS.
+
+See: https://mastodon.social/@sir_pepe/114319751487861964
+
+===
+
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="-1 -1 202 40">
+  <style>
+      [preserveAspectRatio] { fill: yellow; stroke: black; }
+  </style>
+  <svg viewBox="0 0 100 100" preserveAspectRatio="xMidYMid meet">
+    <path d="M50,10 A40,40,1,1,1,50,90 A40,40,1,1,1,50,10 M30,40 Q36,35,42,40 M58,40 Q64,35,70,40 M30,60 Q50,75,70,60 Q50,75,30,60"/>
+  </svg>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="-1 -1 202 40">
+    <style>
+        [preserveAspectRatio] { fill: yellow; stroke: black; }
+    </style>
+    <svg viewBox="0 0 100 100" preserveAspectRatio="xMidYMid meet">
+        <path d="M50,10 A40,40,1,1,1,50,90 A40,40,1,1,1,50,10 M30,40 Q36,35,42,40 M58,40 Q64,35,70,40 M30,60 Q50,75,70,60 Q50,75,30,60"/>
+    </svg>
+</svg>