fix(runtime): scoped slot append/prepend correct order after interaction

src/runtime/dom-extras.ts

@@ -83,6 +83,12 @@ export const patchSlotAppendChild = (HostElementPrototype: any) => {
     const slotName = (newChild['s-sn'] = getSlotName(newChild));
     const slotNode = getHostSlotNode(this.childNodes, slotName, this.tagName);
     if (slotNode) {
+      const slotPlaceholder: d.RenderNode = document.createTextNode('') as any;
+      slotPlaceholder['s-nr'] = newChild;
+      (slotNode['s-cr'].parentNode as any).__appendChild(slotPlaceholder);
+      newChild['s-ol'] = slotPlaceholder;
+      newChild['s-sh'] = slotNode['s-hn'];
+
       const slotChildNodes = getHostSlotChildNodes(slotNode, slotName);
       const appendAfter = slotChildNodes[slotChildNodes.length - 1];
       const insertedNode = insertBefore(appendAfter.parentNode, newChild, appendAfter.nextSibling);
@@ -147,6 +153,7 @@ export const patchSlotPrepend = (HostElementPrototype: HTMLElement) => {
         slotPlaceholder['s-nr'] = newChild;
         (slotNode['s-cr'].parentNode as any).__appendChild(slotPlaceholder);
         newChild['s-ol'] = slotPlaceholder;
+        newChild['s-sh'] = slotNode['s-hn'];
 
         const slotChildNodes = getHostSlotChildNodes(slotNode, slotName);
         const appendAfter = slotChildNodes[0];

test/wdio/scoped-slot-insertion-order-after-interaction/cmp.test.tsx

@@ -0,0 +1,117 @@
+import { Fragment, h } from '@stencil/core';
+import { render } from '@wdio/browser-runner/stencil';
+
+describe('scoped-slot-insertion-order-after-interaction', () => {
+  let host: HTMLScopedSlotInsertionOrderAfterInteractionElement;
+
+  beforeEach(async () => {
+    render({
+      template: () => (
+        <>
+          <scoped-slot-insertion-order-after-interaction>
+            <p>My initial slotted content.</p>
+          </scoped-slot-insertion-order-after-interaction>
+
+          <button type="button" id="appendNodes">
+            append nodes via "append"
+          </button>
+          <button type="button" id="appendChildNodes">
+            append nodes via "appendChild"
+          </button>
+          <button type="button" id="prependNodes">
+            prepend nodes
+          </button>
+        </>
+      ),
+    });
+
+    const scopedSlotInsertionOrderAfterInteraction = document.querySelector(
+      'scoped-slot-insertion-order-after-interaction',
+    );
+
+    // The element to be inserted
+    const el = document.createElement('p');
+    el.innerText = 'The new slotted content.';
+
+    await $('#appendNodes').waitForExist();
+    document.querySelector('#appendNodes').addEventListener('click', () => {
+      scopedSlotInsertionOrderAfterInteraction.append(el);
+    });
+
+    document.querySelector('#appendChildNodes').addEventListener('click', () => {
+      scopedSlotInsertionOrderAfterInteraction.appendChild(el);
+    });
+
+    document.querySelector('#prependNodes').addEventListener('click', () => {
+      scopedSlotInsertionOrderAfterInteraction.prepend(el);
+    });
+
+    host = document.querySelector('scoped-slot-insertion-order-after-interaction');
+  });
+
+  describe('append', () => {
+    it('inserts a DOM element at the end of the slot', async () => {
+      expect(host).toBeDefined();
+
+      await browser.waitUntil(async () => host.children.length === 1);
+      expect(host.children[0].textContent).toBe('My initial slotted content.');
+
+      const addButton = $('#appendNodes');
+      await addButton.click();
+
+      await browser.waitUntil(async () => host.children.length === 2);
+      expect(host.children[0].textContent).toBe('My initial slotted content.');
+      expect(host.children[1].textContent).toBe('The new slotted content.');
+
+      const text = $('p');
+      await text.click();
+      await browser.waitUntil(async () => host.dataset.counter === '1');
+      expect(host.children[0].textContent).toBe('My initial slotted content.');
+      expect(host.children[1].textContent).toBe('The new slotted content.');
+    });
+  });
+
+  describe('appendChild', () => {
+    it('inserts a DOM element at the end of the slot', async () => {
+      expect(host).toBeDefined();
+
+      await browser.waitUntil(async () => host.children.length === 1);
+      expect(host.children[0].textContent).toBe('My initial slotted content.');
+
+      const addButton = $('#appendChildNodes');
+      await addButton.click();
+
+      await browser.waitUntil(async () => host.children.length === 2);
+      expect(host.children[0].textContent).toBe('My initial slotted content.');
+      expect(host.children[1].textContent).toBe('The new slotted content.');
+
+      const text = $('p');
+      await text.click();
+      await browser.waitUntil(async () => host.dataset.counter === '1');
+      expect(host.children[0].textContent).toBe('My initial slotted content.');
+      expect(host.children[1].textContent).toBe('The new slotted content.');
+    });
+  });
+
+  describe('prepend', () => {
+    it('inserts a DOM element at the start of the slot', async () => {
+      expect(host).toBeDefined();
+
+      await browser.waitUntil(async () => host.children.length === 1);
+      expect(host.children[0].textContent).toBe('My initial slotted content.');
+
+      const addButton = $('#prependNodes');
+      await addButton.click();
+
+      await browser.waitUntil(async () => host.children.length === 2);
+      expect(host.children[0].textContent).toBe('The new slotted content.');
+      expect(host.children[1].textContent).toBe('My initial slotted content.');
+
+      const text = $('p');
+      await text.click();
+      await browser.waitUntil(async () => host.dataset.counter === '1');
+      expect(host.children[0].textContent).toBe('The new slotted content.');
+      expect(host.children[1].textContent).toBe('My initial slotted content.');
+    });
+  });
+});

test/wdio/scoped-slot-insertion-order-after-interaction/cmp.tsx

@@ -0,0 +1,22 @@
+import { Component, h, Host, State } from '@stencil/core';
+
+@Component({
+  tag: 'scoped-slot-insertion-order-after-interaction',
+  scoped: true,
+})
+export class ScopedSlotInsertionOrderAfterInteraction {
+  @State() totalCounter = 0;
+
+  render() {
+    return (
+      <Host
+        data-counter={this.totalCounter}
+        onClick={() => {
+          this.totalCounter = this.totalCounter + 1;
+        }}
+      >
+        <slot></slot>
+      </Host>
+    );
+  }
+}