fix(ssr): stop stripping comment nodes

src/runtime/client-hydrate.ts

@@ -220,13 +220,6 @@ export const initializeClientHydrate = (
     for (rnIdex; rnIdex < rnLen; rnIdex++) {
       shadowRoot.appendChild(shadowRootNodes[rnIdex] as any);
     }
-
-    // Tidy up left-over / unnecessary comments to stop frameworks complaining about DOM mismatches
-    Array.from(hostElm.childNodes).forEach((node) => {
-      if (node.nodeType === NODE_TYPE.CommentNode && typeof (node as d.RenderNode)['s-sn'] !== 'string') {
-        node.parentNode.removeChild(node);
-      }
-    });
   }
 
   hostRef.$hostElement$ = hostElm;

src/runtime/test/hydrate-shadow-child.spec.tsx

@@ -454,7 +454,7 @@ describe('hydrate, shadow child', () => {
         );
       }
     }
-    // @ts-ignore
+
     const serverHydrated = await newSpecPage({
       components: [CmpA, CmpB, CmpC],
       html: `
@@ -467,6 +467,7 @@ describe('hydrate, shadow child', () => {
       `,
       hydrateServerSide: true,
     });
+
     expect(serverHydrated.root).toEqualHtml(`
       <cmp-a class="hydrated" s-id="1">
         <!--r.1-->
@@ -522,35 +523,78 @@ describe('hydrate, shadow child', () => {
     `);
   });
 
-  it('test shadow root innerHTML', async () => {
+  it('preserves all nodes', async () => {
     @Component({
       tag: 'cmp-a',
       shadow: true,
     })
     class CmpA {
       render() {
-        return <div>Shadow Content</div>;
+        return <slot>Shadow Content</slot>;
       }
     }
 
-    const page = await newSpecPage({
+    const serverHydrated = await newSpecPage({
       components: [CmpA],
       html: `
         <cmp-a>
-          Light Content
+          A text node
+          <!-- a comment -->
+          <div>An element</div>
+          <!-- another comment -->
+          Another text node
         </cmp-a>
       `,
+      hydrateServerSide: true,
     });
 
-    expect(page.root).toEqualHtml(`
-      <cmp-a>
+    expect(serverHydrated.root).toEqualHtml(`
+      <cmp-a class=\"hydrated\" s-id=\"1\">
+        <!--r.1-->
+        <!--o.0.1.-->
+        <!--o.0.2.-->
+        <!--o.0.4.-->
+        <!--o.0.6.-->
+        <!--o.0.7.-->
+        <slot-fb c-id=\"1.0.0.0\" hidden=\"\" s-sn=\"\">
+          <!--t.1.1.1.0-->
+          Shadow Content
+        </slot-fb>
+        <!--t.0.1-->
+        A text node
+        <!--c.0.2-->
+        <!-- a comment -->
+        <div c-id=\"0.4\" s-sn=\"\">
+          An element
+        </div>
+        <!--c.0.6-->
+        <!-- another comment -->
+        <!--t.0.7-->
+        Another text node
+      </cmp-a>  
+    `);
+
+    const clientHydrated = await newSpecPage({
+      components: [CmpA],
+      html: serverHydrated.root.outerHTML,
+      hydrateClientSide: true,
+    });
+
+    expect(clientHydrated.root).toEqualHtml(`
+      <cmp-a class=\"hydrated\">
         <mock:shadow-root>
-          <div>
+          <slot>
             Shadow Content
-          </div>
+          </slot>
         </mock:shadow-root>
-        Light Content
-      </cmp-a>
+        A text node
+        <!-- a comment -->
+        <div>
+          An element
+        </div>
+        <!-- another comment -->
+        Another text node
+      </cmp-a>  
     `);
   });
 });

src/runtime/test/hydrate-shadow-in-shadow.spec.tsx

@@ -60,6 +60,7 @@ describe('hydrate, shadow in shadow', () => {
             <mock:shadow-root>
               <slot></slot>
             </mock:shadow-root>
+            <!---->
             <slot></slot>
           </cmp-b>
         </mock:shadow-root>

src/runtime/test/shadow.spec.tsx

@@ -135,4 +135,36 @@ describe('shadow', () => {
     expect(page.root).toEqualHtml(expected);
     expect(page.root).toEqualLightHtml(expected);
   });
+
+  it('test shadow root innerHTML', async () => {
+    @Component({
+      tag: 'cmp-a',
+      shadow: true,
+    })
+    class CmpA {
+      render() {
+        return <div>Shadow Content</div>;
+      }
+    }
+
+    const page = await newSpecPage({
+      components: [CmpA],
+      html: `
+        <cmp-a>
+          Light Content
+        </cmp-a>
+      `,
+    });
+
+    expect(page.root).toEqualHtml(`
+      <cmp-a>
+        <mock:shadow-root>
+          <div>
+            Shadow Content
+          </div>
+        </mock:shadow-root>
+        Light Content
+      </cmp-a>
+    `);
+  });
 });

test/wdio/ssr-hydration/cmp.test.tsx

@@ -0,0 +1,59 @@
+import { renderToString } from '../hydrate/index.mjs';
+
+describe('ssr-shadow-cmp', () => {
+  function getNodeNames(chidNodes: NodeListOf<ChildNode>) {
+    return Array.from(chidNodes)
+      .flatMap((node) => {
+        if (node.nodeType === 3) {
+          if (node.textContent?.trim()) {
+            return 'text';
+          } else {
+            return [];
+          }
+        } else if (node.nodeType === 8) {
+          return 'comment';
+        } else {
+          return node.nodeName.toLowerCase();
+        }
+      })
+      .join(' ');
+  }
+
+  it('verifies all nodes are preserved during hydration', async () => {
+    if (!document.querySelector('#stage')) {
+      const { html } = await renderToString(
+        `
+        <ssr-shadow-cmp>
+          A text node
+          <!-- a comment -->
+          <div>An element</div>
+          <!-- another comment -->
+          Another text node
+        </ssr-shadow-cmp>
+      `,
+        {
+          fullDocument: true,
+          serializeShadowRoot: true,
+          constrainTimeouts: false,
+        },
+      );
+      const stage = document.createElement('div');
+      stage.setAttribute('id', 'stage');
+      stage.setHTMLUnsafe(html);
+      document.body.appendChild(stage);
+    }
+
+    // @ts-expect-error resolved through WDIO
+    const { defineCustomElements } = await import('/dist/loader/index.js');
+    defineCustomElements().catch(console.error);
+
+    // wait for Stencil to take over and reconcile
+    await browser.waitUntil(async () => customElements.get('ssr-shadow-cmp'));
+    expect(typeof customElements.get('ssr-shadow-cmp')).toBe('function');
+    await expect(getNodeNames(document.querySelector('ssr-shadow-cmp').childNodes)).toBe(
+      `text comment div comment text`,
+    );
+
+    document.querySelector('#stage')?.remove();
+  });
+});

test/wdio/ssr-hydration/cmp.tsx

@@ -0,0 +1,15 @@
+import { Component, h } from '@stencil/core';
+
+@Component({
+  tag: 'ssr-shadow-cmp',
+  shadow: true,
+})
+export class SsrShadowCmp {
+  render() {
+    return (
+      <div>
+        <slot />
+      </div>
+    );
+  }
+}