feat(runtime): add slotchange event and assignedNodes / assignedElements methods for scoped: true slots

src/declarations/stencil-private.ts

@@ -1440,7 +1440,7 @@ export interface RenderNode extends HostElement {
 
   /**
    * Node reference:
-   * This is a reference for a original location node
+   * This is a reference from an original location node
    * back to the node that's been moved around.
    */
   ['s-nr']?: PatchedSlotNode | RenderNode;

src/runtime/client-hydrate.ts

@@ -16,7 +16,7 @@ import {
   TEXT_NODE_ID,
   VNODE_FLAGS,
 } from './runtime-constants';
-import { addSlotRelocateNode } from './slot-polyfill-utils';
+import { addSlotRelocateNode, patchSlotNode } from './slot-polyfill-utils';
 import { newVNode } from './vdom/h';
 
 /**
@@ -615,6 +615,7 @@ function addSlot(
 
     // attempt to find any mock slotted nodes which we'll move later
     addSlottedNodes(slottedNodes, slotId, slotName, node, shouldMove ? parentNodeId : childVNode.$hostId$);
+    patchSlotNode(node);
 
     if (shouldMove) {
       // Move slot comment node (to after any other comment nodes)

src/runtime/dom-extras.ts

@@ -4,8 +4,10 @@ import { supportsShadow } from '@platform';
 import type * as d from '../declarations';
 import {
   addSlotRelocateNode,
-  getHostSlotChildNodes,
+  dispatchSlotChangeEvent,
+  findSlotFromSlottedNode,
   getHostSlotNodes,
+  getSlotChildSiblings,
   getSlotName,
   getSlottedChildNodes,
   updateFallbackSlotVisibility,
@@ -90,22 +92,18 @@ export const patchCloneNode = (HostElementPrototype: HTMLElement) => {
  */
 export const patchSlotAppendChild = (HostElementPrototype: any) => {
   HostElementPrototype.__appendChild = HostElementPrototype.appendChild;
+
   HostElementPrototype.appendChild = function (this: d.RenderNode, newChild: d.RenderNode) {
-    const slotName = (newChild['s-sn'] = getSlotName(newChild));
-    const slotNode = getHostSlotNodes((this as any).__childNodes || this.childNodes, this.tagName, slotName)[0];
+    const { slotName, slotNode } = findSlotFromSlottedNode(newChild, this);
     if (slotNode) {
       addSlotRelocateNode(newChild, slotNode);
 
-      const slotChildNodes = getHostSlotChildNodes(slotNode, slotName);
+      const slotChildNodes = getSlotChildSiblings(slotNode, slotName);
       const appendAfter = slotChildNodes[slotChildNodes.length - 1];
 
-      const parent = intrnlCall(appendAfter, 'parentNode') as d.RenderNode;
-      let insertedNode: d.RenderNode;
-      if (parent.__insertBefore) {
-        insertedNode = parent.__insertBefore(newChild, appendAfter.nextSibling);
-      } else {
-        insertedNode = parent.insertBefore(newChild, appendAfter.nextSibling);
-      }
+      const parent = internalCall(appendAfter, 'parentNode') as d.RenderNode;
+      const insertedNode: d.RenderNode = internalCall(parent, 'insertBefore')(newChild, appendAfter.nextSibling);
+      dispatchSlotChangeEvent(slotNode);
 
       // Check if there is fallback content that should be hidden
       updateFallbackSlotVisibility(this);
@@ -155,20 +153,18 @@ export const patchSlotPrepend = (HostElementPrototype: HTMLElement) => {
       if (typeof newChild === 'string') {
         newChild = this.ownerDocument.createTextNode(newChild) as unknown as d.RenderNode;
       }
-      const slotName = (newChild['s-sn'] = getSlotName(newChild));
-      const childNodes = (this as any).__childNodes || this.childNodes;
+      const slotName = (newChild['s-sn'] = getSlotName(newChild)) || '';
+      const childNodes = internalCall(this, 'childNodes');
       const slotNode = getHostSlotNodes(childNodes, this.tagName, slotName)[0];
       if (slotNode) {
         addSlotRelocateNode(newChild, slotNode, true);
-        const slotChildNodes = getHostSlotChildNodes(slotNode, slotName);
+        const slotChildNodes = getSlotChildSiblings(slotNode, slotName);
         const appendAfter = slotChildNodes[0];
-        const parent = intrnlCall(appendAfter, 'parentNode') as d.RenderNode;
 
-        if (parent.__insertBefore) {
-          return parent.__insertBefore(newChild, intrnlCall(appendAfter, 'nextSibling'));
-        } else {
-          return parent.insertBefore(newChild, intrnlCall(appendAfter, 'nextSibling'));
-        }
+        const parent = internalCall(appendAfter, 'parentNode') as d.RenderNode;
+        const toReturn = internalCall(parent, 'insertBefore')(newChild, internalCall(appendAfter, 'nextSibling'));
+        dispatchSlotChangeEvent(slotNode);
+        return toReturn;
       }
 
       if (newChild.nodeType === 1 && !!newChild.getAttribute('slot')) {
@@ -263,8 +259,7 @@ const patchInsertBefore = (HostElementPrototype: HTMLElement) => {
     newChild: T,
     currentChild: d.RenderNode | null,
   ) {
-    const slotName = (newChild['s-sn'] = getSlotName(newChild));
-    const slotNode = getHostSlotNodes(this.__childNodes, this.tagName, slotName)[0];
+    const { slotName, slotNode } = findSlotFromSlottedNode(newChild, this);
     const slottedNodes = this.__childNodes ? this.childNodes : getSlottedChildNodes(this.childNodes);
 
     if (slotNode) {
@@ -286,13 +281,10 @@ const patchInsertBefore = (HostElementPrototype: HTMLElement) => {
             // current child ('slot before' node) is 'in' the same slot
             addSlotRelocateNode(newChild, slotNode);
 
-            const parent = intrnlCall(currentChild, 'parentNode') as d.RenderNode;
-            if (parent.__insertBefore) {
-              // the parent is a patched component, so we need to use the internal method
-              parent.__insertBefore(newChild, currentChild);
-            } else {
-              parent.insertBefore(newChild, currentChild);
-            }
+            const parent = internalCall(currentChild, 'parentNode') as d.RenderNode;
+            internalCall(parent, 'insertBefore')(newChild, currentChild);
+
+            dispatchSlotChangeEvent(slotNode);
           }
           return;
         }
@@ -432,7 +424,7 @@ export const patchChildSlotNodes = (elm: HTMLElement) => {
  * @param node the slotted node to be patched
  */
 export const patchSlottedNode = (node: Node) => {
-  if (!node || (node as any).__nextSibling || !globalThis.Node) return;
+  if (!node || (node as any).__nextSibling !== undefined || !globalThis.Node) return;
 
   patchNextSibling(node);
   patchPreviousSibling(node);
@@ -595,10 +587,13 @@ function patchHostOriginalAccessor(
  *
  * @returns the original accessor or method of the node
  */
-function intrnlCall<T extends d.RenderNode, P extends keyof d.RenderNode>(node: T, method: P): T[P] {
+export function internalCall<T extends d.RenderNode, P extends keyof d.RenderNode>(node: T, method: P): T[P] {
   if ('__' + method in node) {
-    return node[('__' + method) as keyof d.RenderNode] as T[P];
+    const toReturn = node[('__' + method) as keyof d.RenderNode] as T[P];
+    if (typeof toReturn !== 'function') return toReturn;
+    return toReturn.bind(node) as T[P];
   } else {
-    return node[method];
+    if (typeof node[method] !== 'function') return node[method];
+    return node[method].bind(node) as T[P];
   }
 }

src/runtime/slot-polyfill-utils.ts

@@ -1,11 +1,12 @@
 import { BUILD } from '@app-data';
 
 import type * as d from '../declarations';
+import { internalCall } from './dom-extras';
 import { NODE_TYPE } from './runtime-constants';
 
 /**
  * Adjust the `.hidden` property as-needed on any nodes in a DOM subtree which
- * are slot fallbacks nodes - `<slot-fb>...</slot-fb>`
+ * are slot fallback nodes - `<slot-fb>...</slot-fb>`
  *
  * A slot fallback node should be visible by default. Then, it should be
  * conditionally hidden if:
@@ -17,15 +18,15 @@ import { NODE_TYPE } from './runtime-constants';
  * @param elm the element of interest
  */
 export const updateFallbackSlotVisibility = (elm: d.RenderNode) => {
-  const childNodes: d.RenderNode[] = elm.__childNodes || (elm.childNodes as any);
+  const childNodes = internalCall(elm, 'childNodes');
 
   // is this is a stencil component?
   if (elm.tagName && elm.tagName.includes('-') && elm['s-cr'] && elm.tagName !== 'SLOT-FB') {
     // stencil component - try to find any slot fallback nodes
     getHostSlotNodes(childNodes as any, (elm as HTMLElement).tagName).forEach((slotNode) => {
       if (slotNode.nodeType === NODE_TYPE.ElementNode && slotNode.tagName === 'SLOT-FB') {
         // this is a slot fallback node
-        if (getHostSlotChildNodes(slotNode, slotNode['s-sn'], false)?.length) {
+        if (getSlotChildSiblings(slotNode, getSlotName(slotNode), false)?.length) {
           // has slotted nodes, hide fallback
           slotNode.hidden = true;
         } else {
@@ -35,8 +36,11 @@ export const updateFallbackSlotVisibility = (elm: d.RenderNode) => {
       }
     });
   }
-  for (const childNode of childNodes) {
-    if (childNode.nodeType === NODE_TYPE.ElementNode && (childNode.__childNodes || childNode.childNodes).length) {
+
+  let i = 0;
+  for (i = 0; i < childNodes.length; i++) {
+    const childNode = childNodes[i] as d.RenderNode;
+    if (childNode.nodeType === NODE_TYPE.ElementNode && internalCall(childNode, 'childNodes').length) {
       // keep drilling down
       updateFallbackSlotVisibility(childNode);
     }
@@ -54,7 +58,7 @@ export const updateFallbackSlotVisibility = (elm: d.RenderNode) => {
  * @returns An array of slotted reference nodes.
  */
 export const getSlottedChildNodes = (childNodes: NodeListOf<ChildNode>): d.PatchedSlotNode[] => {
-  const result = [];
+  const result: d.PatchedSlotNode[] = [];
   for (let i = 0; i < childNodes.length; i++) {
     const slottedNode = ((childNodes[i] as d.RenderNode)['s-nr'] as d.PatchedSlotNode) || undefined;
     if (slottedNode && slottedNode.isConnected) {
@@ -71,7 +75,7 @@ export const getSlottedChildNodes = (childNodes: NodeListOf<ChildNode>): d.Patch
  * @param slotName the name of the slot to match on.
  * @returns a reference to the slot node that matches the provided name, `null` otherwise
  */
-export function getHostSlotNodes(childNodes: NodeListOf<ChildNode>, hostName: string, slotName?: string) {
+export function getHostSlotNodes(childNodes: NodeListOf<ChildNode>, hostName?: string, slotName?: string) {
   let i = 0;
   let slottedNodes: d.RenderNode[] = [];
   let childNode: d.RenderNode;
@@ -80,8 +84,8 @@ export function getHostSlotNodes(childNodes: NodeListOf<ChildNode>, hostName: st
     childNode = childNodes[i] as any;
     if (
       childNode['s-sr'] &&
-      childNode['s-hn'] === hostName &&
-      (slotName === undefined || childNode['s-sn'] === slotName)
+      (!hostName || childNode['s-hn'] === hostName) &&
+      (slotName === undefined || getSlotName(childNode) === slotName)
     ) {
       slottedNodes.push(childNode);
       if (typeof slotName !== 'undefined') return slottedNodes;
@@ -92,18 +96,19 @@ export function getHostSlotNodes(childNodes: NodeListOf<ChildNode>, hostName: st
 }
 
 /**
- * Get slotted child nodes of a slot node
- * @param node - the slot node to get the child nodes from
+ * Get all 'child' sibling nodes of a slot node
+ * @param slot - the slot node to get the child nodes from
  * @param slotName - the name of the slot to match on
  * @param includeSlot - whether to include the slot node in the result
- * @returns slotted child nodes of the slot node
+ * @returns child nodes of the slot node
  */
-export const getHostSlotChildNodes = (node: d.RenderNode, slotName: string, includeSlot = true) => {
+export const getSlotChildSiblings = (slot: d.RenderNode, slotName: string, includeSlot = true) => {
   const childNodes: d.RenderNode[] = [];
-  if ((includeSlot && node['s-sr']) || !node['s-sr']) childNodes.push(node as any);
+  if ((includeSlot && slot['s-sr']) || !slot['s-sr']) childNodes.push(slot as any);
+  let node = slot;
 
-  while ((node = node.nextSibling as any) && (node as d.RenderNode)['s-sn'] === slotName) {
-    childNodes.push(node as any);
+  while ((node = node.nextSibling as any)) {
+    if (getSlotName(node) === slotName) childNodes.push(node as any);
   }
   return childNodes;
 };
@@ -150,37 +155,34 @@ export const addSlotRelocateNode = (
   prepend?: boolean,
   position?: number,
 ) => {
-  let slottedNodeLocation: d.RenderNode;
-
-  // does newChild already have a slot location node?
   if (newChild['s-ol'] && newChild['s-ol'].isConnected) {
-    slottedNodeLocation = newChild['s-ol'];
-  } else {
-    slottedNodeLocation = document.createTextNode('') as any;
-    slottedNodeLocation['s-nr'] = newChild;
+    // newChild already has a slot location node
+    return;
   }
 
+  const slottedNodeLocation = document.createTextNode('') as any;
+  slottedNodeLocation['s-nr'] = newChild;
+
+  // if there's no content reference node, or parentNode we can't do anything
   if (!slotNode['s-cr'] || !slotNode['s-cr'].parentNode) return;
 
   const parent = slotNode['s-cr'].parentNode as any;
-  const appendMethod = prepend ? parent.__prepend || parent.prepend : parent.__appendChild || parent.appendChild;
-
-  if (typeof position !== 'undefined') {
-    if (BUILD.hydrateClientSide) {
-      slottedNodeLocation['s-oo'] = position;
-      const childNodes = (parent.__childNodes || parent.childNodes) as NodeListOf<d.RenderNode>;
-      const slotRelocateNodes: d.RenderNode[] = [slottedNodeLocation];
-      childNodes.forEach((n) => {
-        if (n['s-nr']) slotRelocateNodes.push(n);
-      });
+  const appendMethod = prepend ? internalCall(parent, 'prepend') : internalCall(parent, 'appendChild');
 
-      slotRelocateNodes.sort((a, b) => {
-        if (!a['s-oo'] || a['s-oo'] < b['s-oo']) return -1;
-        else if (!b['s-oo'] || b['s-oo'] < a['s-oo']) return 1;
-        return 0;
-      });
-      slotRelocateNodes.forEach((n) => appendMethod.call(parent, n));
-    }
+  if (BUILD.hydrateClientSide && typeof position !== 'undefined') {
+    slottedNodeLocation['s-oo'] = position;
+    const childNodes = internalCall(parent, 'childNodes') as NodeListOf<d.RenderNode>;
+    const slotRelocateNodes: d.RenderNode[] = [slottedNodeLocation];
+    childNodes.forEach((n) => {
+      if (n['s-nr']) slotRelocateNodes.push(n);
+    });
+
+    slotRelocateNodes.sort((a, b) => {
+      if (!a['s-oo'] || a['s-oo'] < (b['s-oo'] || 0)) return -1;
+      else if (!b['s-oo'] || b['s-oo'] < a['s-oo']) return 1;
+      return 0;
+    });
+    slotRelocateNodes.forEach((n) => appendMethod.call(parent, n));
   } else {
     appendMethod.call(parent, slottedNodeLocation);
   }
@@ -190,4 +192,75 @@ export const addSlotRelocateNode = (
 };
 
 export const getSlotName = (node: d.PatchedSlotNode) =>
-  node['s-sn'] || (node.nodeType === 1 && (node as Element).getAttribute('slot')) || '';
+  typeof node['s-sn'] === 'string'
+    ? node['s-sn']
+    : (node.nodeType === 1 && (node as Element).getAttribute('slot')) || undefined;
+
+/**
+ * Add `assignedElements` and `assignedNodes` methods on a fake slot node
+ *
+ * @param node - slot node to patch
+ */
+export function patchSlotNode(node: d.RenderNode) {
+  if ((node as any).assignedElements || (node as any).assignedNodes || !node['s-sr']) return;
+
+  const assignedFactory = (elementsOnly: boolean) =>
+    function (opts?: { flatten: boolean }) {
+      const toReturn: d.RenderNode[] = [];
+      const slotName = this['s-sn'];
+
+      if (opts?.flatten) {
+        console.error(`
+          Flattening is not supported for Stencil non-shadow slots. 
+          You can use \`.childNodes\` to nested slot fallback content.
+          If you have a particular use case, please open an issue on the Stencil repo.
+        `);
+      }
+
+      const parent = this['s-cr'].parentElement as d.RenderNode;
+      // get all light dom nodes
+      const slottedNodes = parent.__childNodes ? parent.childNodes : getSlottedChildNodes(parent.childNodes);
+
+      (slottedNodes as d.RenderNode[]).forEach((n) => {
+        // find all the nodes assigned to slots we care about
+        if (slotName === getSlotName(n)) {
+          toReturn.push(n);
+        }
+      });
+
+      if (elementsOnly) {
+        return toReturn.filter((n) => n.nodeType === NODE_TYPE.ElementNode);
+      }
+      return toReturn;
+    }.bind(node);
+
+  (node as any).assignedElements = assignedFactory(true);
+  (node as any).assignedNodes = assignedFactory(false);
+}
+
+/**
+ * Dispatches a `slotchange` event on a fake `<slot />` node.
+ *
+ * @param elm the slot node to dispatch the event from
+ */
+export function dispatchSlotChangeEvent(elm: d.RenderNode) {
+  elm.dispatchEvent(new CustomEvent('slotchange', { bubbles: false, cancelable: false, composed: false }));
+}
+
+/**
+ * Find the slot node that a slotted node belongs to
+ *
+ * @param slottedNode - the slotted node to find the slot for
+ * @param parentHost - the parent host element of the slotted node
+ * @returns the slot node and slot name
+ */
+export function findSlotFromSlottedNode(slottedNode: d.PatchedSlotNode, parentHost?: HTMLElement) {
+  parentHost = parentHost || slottedNode['s-ol']?.parentElement;
+
+  if (!parentHost) return { slotNode: null, slotName: '' };
+
+  const slotName = (slottedNode['s-sn'] = getSlotName(slottedNode) || '');
+  const childNodes = internalCall(parentHost, 'childNodes');
+  const slotNode = getHostSlotNodes(childNodes, parentHost.tagName, slotName)[0];
+  return { slotNode, slotName };
+}