perf: apply static parts optimization to dynamic text (#4099)

* perf: enable static content optimization for dynamic text

* test: new template-compiler tests

* test: update existing template compiler tests

* test: add karma tests

* chore: update based on review feedback

* chore: update test fixtures

* Update packages/@lwc/template-compiler/src/codegen/codegen.ts

Co-authored-by: Nolan Lawson <nlawson@salesforce.com>

* chore: update based on pr feedback

---------

Co-authored-by: Nolan Lawson <nlawson@salesforce.com>

packages/@lwc/engine-core/src/framework/api.ts

@@ -51,6 +51,7 @@ import {
     VStatic,
     VStaticPart,
     VStaticPartData,
+    VStaticPartType,
     VText,
 } from './vnodes';
 import { getComponentRegisteredName } from './component';
@@ -62,10 +63,14 @@ function addVNodeToChildLWC(vnode: VCustomElement) {
 }
 
 // [s]tatic [p]art
-function sp(partId: number, data: VStaticPartData): VStaticPart {
+function sp(partId: number, data: VStaticPartData | null, text: string | null): VStaticPart {
+    // Static part will always have either text or data, it's guaranteed by the compiler.
+    const type = isNull(text) ? VStaticPartType.Element : VStaticPartType.Text;
     return {
+        type,
         partId,
         data,
+        text,
         elm: undefined, // elm is defined later
     };
 }

packages/@lwc/engine-core/src/framework/hydration.ts

@@ -51,6 +51,8 @@ import {
     isVCustomElement,
     VElementData,
     VStaticPartData,
+    VStaticPartText,
+    isVStaticPartElement,
 } from './vnodes';
 
 import { patchProps } from './modules/props';
@@ -134,7 +136,11 @@ function hydrateNode(node: Node, vnode: VNode, renderer: RendererAPI): Node | nu
 
 const NODE_VALUE_PROP = 'nodeValue';
 
-function textNodeContentsAreEqual(node: Node, vnode: VText, renderer: RendererAPI): boolean {
+function textNodeContentsAreEqual(
+    node: Node,
+    vnode: VText | VStaticPartText,
+    renderer: RendererAPI
+): boolean {
     const { getProperty } = renderer;
     const nodeValue = getProperty(node, NODE_VALUE_PROP);
 
@@ -183,11 +189,20 @@ function hydrateText(node: Node, vnode: VText, renderer: RendererAPI): Node | nu
     if (!hasCorrectNodeType(vnode, node, EnvNodeTypes.TEXT, renderer)) {
         return handleMismatch(node, vnode, renderer);
     }
+    return updateTextContent(node, vnode, vnode.owner, renderer);
+}
+
+function updateTextContent(
+    node: Node,
+    vnode: VText | VStaticPartText,
+    owner: VM,
+    renderer: RendererAPI
+): Node | null {
     if (process.env.NODE_ENV !== 'production') {
         if (!textNodeContentsAreEqual(node, vnode, renderer)) {
             logWarn(
                 'Hydration mismatch: text values do not match, will recover from the difference',
-                vnode.owner
+                owner
             );
         }
     }
@@ -794,7 +809,7 @@ function areCompatibleStaticNodes(client: Node, ssr: Node, vnode: VStatic, rende
 }
 
 function haveCompatibleStaticParts(vnode: VStatic, renderer: RendererAPI) {
-    const { parts } = vnode;
+    const { parts, owner } = vnode;
 
     if (isUndefined(parts)) {
         return true;
@@ -804,12 +819,24 @@ function haveCompatibleStaticParts(vnode: VStatic, renderer: RendererAPI) {
     // 1. It's never the case that `parts` is undefined on the server but defined on the client (or vice-versa)
     // 2. It's never the case that `parts` has one length on the server but another on the client
     for (const part of parts) {
-        const { data, elm } = part;
-        const hasMatchingAttrs = validateAttrs(vnode, elm!, data, renderer, () => true);
-        const hasMatchingStyleAttr = validateStyleAttr(vnode, elm!, data, renderer);
-        const hasMatchingClass = validateClassAttr(vnode, elm!, data, renderer);
-        if (isFalse(hasMatchingAttrs && hasMatchingStyleAttr && hasMatchingClass)) {
-            return false;
+        const { elm } = part;
+        if (isVStaticPartElement(part)) {
+            if (!hasCorrectNodeType<Element>(vnode, elm!, EnvNodeTypes.ELEMENT, renderer)) {
+                return false;
+            }
+            const { data } = part;
+            const hasMatchingAttrs = validateAttrs(vnode, elm, data, renderer, () => true);
+            const hasMatchingStyleAttr = validateStyleAttr(vnode, elm, data, renderer);
+            const hasMatchingClass = validateClassAttr(vnode, elm, data, renderer);
+            if (isFalse(hasMatchingAttrs && hasMatchingStyleAttr && hasMatchingClass)) {
+                return false;
+            }
+        } else {
+            // VStaticPartText
+            if (!hasCorrectNodeType(vnode, elm!, EnvNodeTypes.TEXT, renderer)) {
+                return false;
+            }
+            updateTextContent(elm, part as VStaticPartText, owner, renderer);
         }
     }
     return true;

packages/@lwc/engine-core/src/framework/modules/attrs.ts

@@ -15,13 +15,13 @@ import {
 import { RendererAPI } from '../renderer';
 
 import { EmptyObject } from '../utils';
-import { VBaseElement, VStatic, VStaticPart } from '../vnodes';
+import { VBaseElement, VStatic, VStaticPartElement } from '../vnodes';
 
 const ColonCharCode = 58;
 
 export function patchAttributes(
-    oldVnode: VBaseElement | VStaticPart | null,
-    vnode: VBaseElement | VStaticPart,
+    oldVnode: VBaseElement | VStaticPartElement | null,
+    vnode: VBaseElement | VStaticPartElement,
     renderer: RendererAPI
 ) {
     const { data, elm } = vnode;

packages/@lwc/engine-core/src/framework/modules/computed-class-attr.ts

@@ -16,7 +16,7 @@ import {
 import { RendererAPI } from '../renderer';
 
 import { EmptyObject, SPACE_CHAR } from '../utils';
-import { VBaseElement, VStaticPart } from '../vnodes';
+import { VBaseElement, VStaticPartElement } from '../vnodes';
 
 const classNameToClassMap = create(null);
 
@@ -58,8 +58,8 @@ export function getMapFromClassName(className: string | undefined): Record<strin
 }
 
 export function patchClassAttribute(
-    oldVnode: VBaseElement | VStaticPart | null,
-    vnode: VBaseElement | VStaticPart,
+    oldVnode: VBaseElement | VStaticPartElement | null,
+    vnode: VBaseElement | VStaticPartElement,
     renderer: RendererAPI
 ) {
     const {

packages/@lwc/engine-core/src/framework/modules/computed-style-attr.ts

@@ -6,14 +6,14 @@
  */
 import { isNull, isString, isUndefined } from '@lwc/shared';
 import { RendererAPI } from '../renderer';
-import { VBaseElement, VStaticPart } from '../vnodes';
+import { VBaseElement, VStaticPartElement } from '../vnodes';
 import { logError } from '../../shared/logger';
 import { VM } from '../vm';
 
 // The style property is a string when defined via an expression in the template.
 export function patchStyleAttribute(
-    oldVnode: VBaseElement | VStaticPart | null,
-    vnode: VBaseElement | VStaticPart,
+    oldVnode: VBaseElement | VStaticPartElement | null,
+    vnode: VBaseElement | VStaticPartElement,
     renderer: RendererAPI,
     owner: VM
 ) {

packages/@lwc/engine-core/src/framework/modules/events.ts

@@ -6,9 +6,12 @@
  */
 import { isUndefined } from '@lwc/shared';
 import { RendererAPI } from '../renderer';
-import { VBaseElement, VStaticPart } from '../vnodes';
+import { VBaseElement, VStaticPartElement } from '../vnodes';
 
-export function applyEventListeners(vnode: VBaseElement | VStaticPart, renderer: RendererAPI) {
+export function applyEventListeners(
+    vnode: VBaseElement | VStaticPartElement,
+    renderer: RendererAPI
+) {
     const { elm, data } = vnode;
     const { on } = data;
 

packages/@lwc/engine-core/src/framework/modules/refs.ts

@@ -6,10 +6,10 @@
  */
 import { isUndefined } from '@lwc/shared';
 import { RefVNodes, VM } from '../vm';
-import { VBaseElement, VStaticPart } from '../vnodes';
+import { VBaseElement, VStaticPartElement } from '../vnodes';
 
 // Set a ref (lwc:ref) on a VM, from a template API
-export function applyRefs(vnode: VBaseElement | VStaticPart, owner: VM) {
+export function applyRefs(vnode: VBaseElement | VStaticPartElement, owner: VM) {
     const { data } = vnode;
     const { ref } = data;
 

packages/@lwc/engine-core/src/framework/modules/static-parts.ts

@@ -6,13 +6,21 @@
  */
 
 import { isNull, isUndefined, assert, ArrayShift, ArrayUnshift } from '@lwc/shared';
-import { VStatic, VStaticPart } from '../vnodes';
+import {
+    VStatic,
+    VStaticPart,
+    VStaticPartElement,
+    VStaticPartText,
+    isVStaticPartElement,
+    isVStaticPartText,
+} from '../vnodes';
 import { RendererAPI } from '../renderer';
 import { applyEventListeners } from './events';
 import { applyRefs } from './refs';
 import { patchAttributes } from './attrs';
 import { patchStyleAttribute } from './computed-style-attr';
 import { patchClassAttribute } from './computed-class-attr';
+import { patchTextVStaticPart } from './text';
 
 /**
  * Given an array of static parts, mounts the DOM element to the part based on the staticPartId
@@ -102,13 +110,22 @@ export function mountStaticParts(root: Element, vnode: VStatic, renderer: Render
 
     // Currently only event listeners and refs are supported for static vnodes
     for (const part of parts) {
-        // Event listeners only need to be applied once when mounting
-        applyEventListeners(part, renderer);
-        // Refs must be updated after every render due to refVNodes getting reset before every render
-        applyRefs(part, owner);
-        patchAttributes(null, part, renderer);
-        patchClassAttribute(null, part, renderer);
-        patchStyleAttribute(null, part, renderer, owner);
+        if (isVStaticPartElement(part)) {
+            // Event listeners only need to be applied once when mounting
+            applyEventListeners(part, renderer);
+            // Refs must be updated after every render due to refVNodes getting reset before every render
+            applyRefs(part, owner);
+            patchAttributes(null, part, renderer);
+            patchClassAttribute(null, part, renderer);
+            patchStyleAttribute(null, part, renderer, owner);
+        } else {
+            if (process.env.NODE_ENV !== 'production' && !isVStaticPartText(part)) {
+                throw new Error(
+                    `LWC internal error, encountered unknown static part type: ${part.type}`
+                );
+            }
+            patchTextVStaticPart(null, part as VStaticPartText, renderer);
+        }
     }
 }
 
@@ -144,11 +161,22 @@ export function patchStaticParts(n1: VStatic, n2: VStatic, renderer: RendererAPI
         // Patch only occurs if the vnode is newly generated, which means the part.elm is always undefined
         // Since the vnode and elements are the same we can safely assume that prevParts[i].elm is defined.
         part.elm = prevPart.elm;
-        // Refs must be updated after every render due to refVNodes getting reset before every render
-        applyRefs(part, currPartsOwner);
-        patchAttributes(prevPart, part, renderer);
-        patchClassAttribute(prevPart, part, renderer);
-        patchStyleAttribute(prevPart, part, renderer, currPartsOwner);
+
+        if (process.env.NODE_ENV !== 'production' && prevPart.type !== part.type) {
+            throw new Error(
+                `LWC internal error, static part types do not match. Previous type was ${prevPart.type} and current type is ${part.type}`
+            );
+        }
+
+        if (isVStaticPartElement(part)) {
+            // Refs must be updated after every render due to refVNodes getting reset before every render
+            applyRefs(part, currPartsOwner);
+            patchAttributes(prevPart as VStaticPartElement, part, renderer);
+            patchClassAttribute(prevPart as VStaticPartElement, part, renderer);
+            patchStyleAttribute(prevPart as VStaticPartElement, part, renderer, currPartsOwner);
+        } else {
+            patchTextVStaticPart(null, part as VStaticPartText, renderer);
+        }
     }
 }
 
@@ -171,9 +199,11 @@ export function hydrateStaticParts(vnode: VStatic, renderer: RendererAPI): void
     // which guarantees that the elements are the same.
     // We only need to apply the parts for things that cannot be done on the server.
     for (const part of parts) {
-        // Event listeners only need to be applied once when mounting
-        applyEventListeners(part, renderer);
-        // Refs must be updated after every render due to refVNodes getting reset before every render
-        applyRefs(part, owner);
+        if (isVStaticPartElement(part)) {
+            // Event listeners only need to be applied once when mounting
+            applyEventListeners(part, renderer);
+            // Refs must be updated after every render due to refVNodes getting reset before every render
+            applyRefs(part, owner);
+        }
     }
 }

packages/@lwc/engine-core/src/framework/modules/text.ts

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2024, salesforce.com, inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: MIT
+ * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+ */
+import { isNull } from '@lwc/shared';
+import { RendererAPI } from '../renderer';
+import { lockDomMutation, unlockDomMutation } from '../restrictions';
+import { VComment, VStaticPartText, VText } from '../vnodes';
+
+export function patchTextVNode(n1: VText, n2: VText, renderer: RendererAPI) {
+    n2.elm = n1.elm;
+
+    if (n2.text !== n1.text) {
+        updateTextContent(n2, renderer);
+    }
+}
+
+export function patchTextVStaticPart(
+    n1: VStaticPartText | null,
+    n2: VStaticPartText,
+    renderer: RendererAPI
+) {
+    if (isNull(n1) || n2.text !== n1.text) {
+        updateTextContent(n2, renderer);
+    }
+}
+
+export function updateTextContent(
+    vnode: VText | VComment | VStaticPartText,
+    renderer: RendererAPI
+) {
+    const { elm, text } = vnode;
+    const { setText } = renderer;
+
+    if (process.env.NODE_ENV !== 'production') {
+        unlockDomMutation();
+    }
+    setText(elm, text);
+    if (process.env.NODE_ENV !== 'production') {
+        lockDomMutation();
+    }
+}

packages/@lwc/engine-core/src/framework/rendering.ts

@@ -71,6 +71,7 @@ import { applyStaticStyleAttribute } from './modules/static-style-attr';
 import { applyRefs } from './modules/refs';
 import { mountStaticParts, patchStaticParts } from './modules/static-parts';
 import { LightningElementConstructor } from './base-lightning-element';
+import { patchTextVNode, updateTextContent } from './modules/text';
 
 export function patchChildren(
     c1: VNodes,
@@ -111,7 +112,7 @@ function patch(n1: VNode, n2: VNode, parent: ParentNode, renderer: RendererAPI)
     switch (n2.type) {
         case VNodeType.Text:
             // VText has no special capability, fallback to the owner's renderer
-            patchText(n1 as VText, n2, renderer);
+            patchTextVNode(n1 as VText, n2, renderer);
             break;
 
         case VNodeType.Comment:
@@ -170,14 +171,6 @@ export function mount(node: VNode, parent: ParentNode, renderer: RendererAPI, an
     }
 }
 
-function patchText(n1: VText, n2: VText, renderer: RendererAPI) {
-    n2.elm = n1.elm;
-
-    if (n2.text !== n1.text) {
-        updateTextContent(n2, renderer);
-    }
-}
-
 function mountText(vnode: VText, parent: ParentNode, anchor: Node | null, renderer: RendererAPI) {
     const { owner } = vnode;
     const { createText } = renderer;
@@ -535,19 +528,6 @@ function linkNodeToShadow(elm: Node, owner: VM, renderer: RendererAPI) {
     }
 }
 
-function updateTextContent(vnode: VText | VComment, renderer: RendererAPI) {
-    const { elm, text } = vnode;
-    const { setText } = renderer;
-
-    if (process.env.NODE_ENV !== 'production') {
-        unlockDomMutation();
-    }
-    setText(elm, text);
-    if (process.env.NODE_ENV !== 'production') {
-        lockDomMutation();
-    }
-}
-
 function insertFragmentOrNode(
     vnode: VNode,
     parent: Node,