fix: correctly handle svg class attribute within parseClassList (#6085)

* fix: handle svg class whithin

* add test

---------

Co-authored-by: Dominique Wirz <dominique@smartive.ch>

Author: dwirz

src/runtime/vdom/set-accessor.ts

@@ -198,6 +198,18 @@ const parseClassListRegex = /\s/;
  * @param value className string, e.g. "foo bar baz"
  * @returns list of classes, e.g. ["foo", "bar", "baz"]
  */
-const parseClassList = (value: string | undefined | null): string[] => (!value ? [] : value.split(parseClassListRegex));
+const parseClassList = (value: string | SVGAnimatedString | undefined | null): string[] => {
+  // Can't use `value instanceof SVGAnimatedString` because it'll break in non-browser environments
+  // see https://developer.mozilla.org/docs/Web/API/SVGAnimatedString for more information
+  if (typeof value === 'object' && 'baseVal' in value) {
+    value = value.baseVal;
+  }
+
+  if (!value) {
+    return [];
+  }
+
+  return value.split(parseClassListRegex);
+};
 const CAPTURE_EVENT_SUFFIX = 'Capture';
 const CAPTURE_EVENT_REGEX = new RegExp(CAPTURE_EVENT_SUFFIX + '$');

test/wdio/declarative-shadow-dom/cmp-svg.test.tsx

@@ -0,0 +1,32 @@
+// @ts-ignore may not be existing when project hasn't been built
+type HydrateModule = typeof import('../../hydrate');
+let renderToString: HydrateModule['renderToString'];
+
+describe('custom svg element', function () {
+  let originalConsoleError: typeof console.error;
+  before(async () => {
+    // @ts-ignore may not be existing when project hasn't been built
+    const mod = await import('/hydrate/index.mjs');
+    renderToString = mod.renderToString;
+    originalConsoleError = console.error;
+  });
+
+  after(() => {
+    console.error = originalConsoleError;
+  });
+
+  it('should render without errors', async () => {
+    const errorLogs: string[] = [];
+    console.error = (message) => errorLogs.push(message);
+
+    const { html } = await renderToString(`<custom-svg-element />`, { prettyHtml: true });
+    const stage = document.createElement('div');
+    stage.setAttribute('id', 'stage');
+    stage.setHTMLUnsafe(html);
+    document.body.appendChild(stage);
+
+    await expect($('custom-svg-element')).toHaveText('');
+
+    expect(errorLogs.length).toEqual(0);
+  });
+});

test/wdio/declarative-shadow-dom/cmp-svg.tsx

@@ -0,0 +1,15 @@
+import { Component, h } from '@stencil/core';
+
+@Component({
+  tag: 'custom-svg-element',
+  shadow: true,
+})
+export class CustomSvgElement {
+  render() {
+    return (
+      <svg viewBox="0 0 54 54">
+        <circle cx="8" cy="18" width="54" height="8" r="2" />
+      </svg>
+    );
+  }
+}