From 2105010c7f1f525ab89cc30506219a5dd49a64a7 Mon Sep 17 00:00:00 2001
From: Wesley Luyten <me@wesleyluyten.com>
Date: Wed, 11 Mar 2026 13:36:24 -0500
Subject: [PATCH] fix: attaching media like elements and upgrade (#889)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 package.json                                  |  2 +-
 .../dom/media/custom-media-element/index.ts   |  3 --
 packages/html/src/store/container-mixin.ts    | 41 +++++++++++++------
 3 files changed, 29 insertions(+), 17 deletions(-)

diff --git a/package.json b/package.json
index e97f77e8..9d86e550 100644
--- a/package.json
+++ b/package.json
@@ -26,7 +26,7 @@
     "dev:site": "turbo run dev --filter=site",
     "dev": "turbo run dev --parallel",
     "dev:packages": "turbo run dev --parallel --filter='./packages/*'",
-    "dev:sandbox": "turbo run dev --filter=@videojs/sandbox",
+    "dev:sandbox": "turbo watch dev --filter=@videojs/sandbox",
     "lint": "biome check .",
     "lint:fix": "biome check . --write",
     "lint:fix:file": "biome check --write",
diff --git a/packages/core/src/dom/media/custom-media-element/index.ts b/packages/core/src/dom/media/custom-media-element/index.ts
index 0f6e0a53..99194d69 100644
--- a/packages/core/src/dom/media/custom-media-element/index.ts
+++ b/packages/core/src/dom/media/custom-media-element/index.ts
@@ -434,9 +434,6 @@ export function CustomMediaMixin<T extends Constructor<HTMLElement>>(
 
     connectedCallback(): void {
       this.#init();
-      // Set after #init() so the shadow root exists; safe here since
-      // connectedCallback is spec-compliant for setAttribute (unlike constructor).
-      this.setAttribute('data-media-element', '');
     }
   };
 }
diff --git a/packages/html/src/store/container-mixin.ts b/packages/html/src/store/container-mixin.ts
index 6210c205..d5e6ce27 100644
--- a/packages/html/src/store/container-mixin.ts
+++ b/packages/html/src/store/container-mixin.ts
@@ -46,14 +46,14 @@ export function createContainerMixin<Store extends PlayerStore>(context: PlayerC
         super.connectedCallback();
 
         this.#observer = new MutationObserver((records) => {
-          if (records.some(hasMediaNode)) this.#attachMedia();
+          if (records.some(hasMediaElement)) this.#attachMedia();
         });
 
         this.#observer.observe(this, {
           childList: true,
           subtree: true,
           attributes: true,
-          attributeFilter: ['data-media-element'],
+          attributeFilter: ['name'],
         });
 
         // Slotted media elements don't appear in the container's subtree,
@@ -80,12 +80,18 @@ export function createContainerMixin<Store extends PlayerStore>(context: PlayerC
         if (!slot) return null;
 
         for (const el of slot.assignedElements({ flatten: true })) {
-          if (el instanceof HTMLMediaElement) return el;
+          if (isMediaElement(el)) return el as HTMLMediaElement;
         }
 
         return null;
       }
 
+      #findMediaElement(): HTMLMediaElement | null {
+        const media = Array.from(this.children).find(isMediaElement);
+        if (media) return media as HTMLMediaElement;
+        return null;
+      }
+
       #attachMedia() {
         // Prefer the cached context value; fall back to `this.store` which
         // ProviderMixin overrides when both mixins are applied to one element.
@@ -93,7 +99,7 @@ export function createContainerMixin<Store extends PlayerStore>(context: PlayerC
         if (!store) return;
 
         const media =
-          this.querySelector<HTMLMediaElement>('video, audio, [data-media-element]') ?? this.#getSlottedMedia();
+          this.querySelector<HTMLMediaElement>('video, audio') ?? this.#findMediaElement() ?? this.#getSlottedMedia();
 
         if (!media) {
           this.#detach();
@@ -101,6 +107,10 @@ export function createContainerMixin<Store extends PlayerStore>(context: PlayerC
           return;
         }
 
+        if (isCustomMediaElement(media)) {
+          globalThis.customElements?.upgrade?.(media);
+        }
+
         const target: PlayerTarget = {
           media,
           container: this,
@@ -120,22 +130,27 @@ export function createContainerMixin<Store extends PlayerStore>(context: PlayerC
   };
 }
 
-function isMediaNode(node: Node): boolean {
-  return node instanceof HTMLMediaElement || (node instanceof Element && node.hasAttribute('data-media-element'));
+function isMediaElement(node: Node): boolean {
+  return node instanceof HTMLMediaElement || isCustomMediaElement(node);
 }
 
-function hasMediaNode(record: MutationRecord): boolean {
-  // Attribute mutation: data-media-element was added to a descendant
-  if (record.type === 'attributes' && record.target instanceof Element) {
-    return record.target.hasAttribute('data-media-element');
-  }
+function isCustomMediaElement(node: Node): boolean {
+  return node instanceof HTMLElement && (node.localName.endsWith('-audio') || node.localName.endsWith('-video'));
+}
+
+function isMediaSlotElement(node: Node): boolean {
+  return node instanceof HTMLSlotElement && node.name === 'media';
+}
+
+function hasMediaElement(record: MutationRecord): boolean {
+  if (isMediaSlotElement(record.target)) return true;
 
   for (const node of record.addedNodes) {
-    if (isMediaNode(node)) return true;
+    if (isMediaElement(node) || isMediaSlotElement(node)) return true;
   }
 
   for (const node of record.removedNodes) {
-    if (isMediaNode(node)) return true;
+    if (isMediaElement(node) || isMediaSlotElement(node)) return true;
   }
 
   return false;