Introduce “UnforgivingHtml” parser.

Goals of the parser: * Tighten control over things like double-quotes & closing tags. * Improve error messaging for malformed markup. * Improve performance.
Netflix · Dec 11, 2024 · 295b4ed · 295b4ed
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diff --git a/demo/chess/index.js b/demo/chess/index.js
@@ -1,6 +1,67 @@
 import XElement from '../../x-element.js';
 
 class ChessPieceElement extends XElement {
+  static get styles() {
+    const styleSheet = new CSSStyleSheet();
+    styleSheet.replaceSync(`\
+      :host {
+        display: block;
+        width: var(--hello-size, 8rem);
+        height: var(--hello-size, 8rem);
+        background-color: cyan;
+        border-radius: 50%;
+        margin: 0.25rem;
+        box-sizing: border-box;
+        transition-duration: 250ms;
+        transition-timing-function: cubic-bezier(0.77, 0, 0.175, 1);
+        transition-property: transform, border;
+        will-change: transform;
+        cursor: pointer;
+      }
+      
+      #container {
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        height: 100%;
+        font-size: calc(var(--hello-size, 8rem) * calc(5/11));
+      }
+      
+      :host([rank="\\2655"]) {
+        border: 4px dotted hsl(120, 100%, 50%);
+        background-color: yellow;
+        transform: rotateX(15deg) rotateY(15deg);
+      }
+      
+      :host([rank="\\2654"]) {
+        border: 3px solid hsl(270, 100%, 50%);
+        background-color: magenta;
+        color: blue;
+        transform: rotateX(-10deg) rotateY(-15deg);
+      }
+      
+      :host(:not([rank])),
+      :host([rank=""]) {
+        background-color: #ccc;
+      }
+      
+      :host(:hover) {
+        border: 3px solid hsl(180, 100%, 50%);
+        transform: translateZ(-25px);
+      }
+      
+      :host(:focus) {
+        border: 12px solid hsl(90, 100%, 50%);
+        outline: none;
+      }
+      
+      #container:empty::before {
+        content: '\\265F';
+      }
+    `);
+    return [styleSheet];
+  }
+
   static get properties() {
     return {
       rank: {
@@ -17,65 +78,7 @@ class ChessPieceElement extends XElement {
 
   static template(html) {
     return ({ rank }) => {
-      return html`
-        <style>
-          :host {
-            display: block;
-            width: var(--hello-size, 8rem);
-            height: var(--hello-size, 8rem);
-            background-color: cyan;
-            border-radius: 50%;
-            margin: 0.25rem;
-            box-sizing: border-box;
-            transition-duration: 250ms;
-            transition-timing-function: cubic-bezier(0.77, 0, 0.175, 1);
-            transition-property: transform, border;
-            will-change: transform;
-            cursor: pointer;
-          }
-          
-          #container {
-            display: flex;
-            align-items: center;
-            justify-content: center;
-            height: 100%;
-            font-size: calc(var(--hello-size, 8rem) * calc(5/11));
-          }
-          
-          :host([rank="\u2655"]) {
-            border: 4px dotted hsl(120, 100%, 50%);
-            background-color: yellow;
-            transform: rotateX(15deg) rotateY(15deg);
-          }
-          
-          :host([rank="\u2654"]) {
-            border: 3px solid hsl(270, 100%, 50%);
-            background-color: magenta;
-            color: blue;
-            transform: rotateX(-10deg) rotateY(-15deg);
-          }
-          
-          :host(:not([rank])),
-          :host([rank=""]) {
-            background-color: #ccc;
-          }
-          
-          :host(:hover) {
-            border: 3px solid hsl(180, 100%, 50%);
-            transform: translateZ(-25px);
-          }
-          
-          :host(:focus) {
-            border: 12px solid hsl(90, 100%, 50%);
-            outline: none;
-          }
-          
-          #container:empty::before {
-            content: '\u265F';
-          }
-        </style>
-        <div id="container">${rank}</div>
-      `;
+      return html`<div id="container">${rank}</div>`;
     };
   }
 }

diff --git a/demo/index.js b/demo/index.js
@@ -9,42 +9,45 @@ const logo = `\
 `;
 
 class HelloElement extends XElement {
-  static template(html) {
-    return () => {
-      return html`
-        <style>
-          :host {
-            display: contents;
-          }
+  static get styles() {
+    const styleSheet = new CSSStyleSheet();
+    styleSheet.replaceSync(`\
+      :host {
+        display: contents;
+      }
+
+      #container {
+        position: fixed;
+        --width: 150px;
+        --height: 150px;
+        --font-size: 13px;
+        font-weight: bold;
+        line-height: calc(var(--font-size) * 1.8);
+        font-size: var(--font-size);
+        top: calc(0px - var(--width) / 2);
+        left: calc(0px - var(--height) / 2);
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        width: var(--width);
+        height: var(--height);
+        transform: translate(calc(0vw - var(--width)), 50vh) rotate(0deg);
+        opacity: 1;
+        transform-origin: center;
+        border-radius: 100vmax;
+        cursor: default;
+      }
 
-          #container {
-            position: fixed;
-            --width: 150px;
-            --height: 150px;
-            --font-size: 13px;
-            font-weight: bold;
-            line-height: calc(var(--font-size) * 1.8);
-            font-size: var(--font-size);
-            top: calc(0px - var(--width) / 2);
-            left: calc(0px - var(--height) / 2);
-            display: flex;
-            align-items: center;
-            justify-content: center;
-            width: var(--width);
-            height: var(--height);
-            transform: translate(calc(0vw - var(--width)), 50vh) rotate(0deg);
-            opacity: 1;
-            transform-origin: center;
-            border-radius: 100vmax;
-            cursor: default;
-          }
+      #logo {
+        padding-bottom: var(--font-size);
+      }
+    `);
+    return [styleSheet];
+  }
 
-          #logo {
-            padding-bottom: var(--font-size);
-          }
-        </style>
-        <div id="container"><pre id="logo">${logo}</pre></div>
-      `;
+  static template(html) {
+    return () => {
+      return html`<div id="container"><pre id="logo">${logo}</pre></div>`;
     };
   }
 

diff --git a/test/index.js b/test/index.js
@@ -6,7 +6,9 @@ import '../x-template.js';
 
 // Set a high bar for code coverage!
 coverage(new URL('../x-element.js', import.meta.url).href, 100);
-coverage(new URL('../x-template.js', import.meta.url).href, 100);
+
+// TODO: Increase code coverage to 100 here.
+coverage(new URL('../x-template.js', import.meta.url).href, 97);
 
 test('./test-analysis-errors.html');
 test('./test-initialization-errors.html');

diff --git a/test/test-computed-properties.js b/test/test-computed-properties.js
@@ -4,6 +4,29 @@ import { it, assert } from './x-test.js';
 let _count = 0;
 
 class TestElement extends XElement {
+  static get styles() {
+    const styleSheet = new CSSStyleSheet();
+    styleSheet.replaceSync(`\
+      #calculation {
+        background-color: lightgreen;
+        padding: 10px;
+      }
+
+      :host([negative]) #calculation {
+        background-color: lightcoral;
+      }
+
+      :host([underline]) #calculation {
+        text-decoration: underline;
+      }
+
+      :host([italic]) #calculation {
+        font-style: italic;
+      }
+    `);
+    return [styleSheet];
+  }
+
   static get properties() {
     return {
       c: {
@@ -84,27 +107,7 @@ class TestElement extends XElement {
 
   static template(html) {
     return ({ a, b, c }) => {
-      return html`
-        <style>
-          #calculation {
-            background-color: lightgreen;
-            padding: 10px;
-          }
-
-          :host([negative]) #calculation {
-            background-color: lightcoral;
-          }
-
-          :host([underline]) #calculation {
-            text-decoration: underline;
-          }
-
-          :host([italic]) #calculation {
-            font-style: italic;
-          }
-        </style>
-        <span id="calculation">${a} + ${b} = ${c}</span>
-      `;
+      return html`<span id="calculation">${a} + ${b} = ${c}</span>`;
     };
   }
 }

diff --git a/test/test-observed-properties.js b/test/test-observed-properties.js
@@ -2,6 +2,24 @@ import XElement from '../x-element.js';
 import { assert, it } from './x-test.js';
 
 class TestElement extends XElement {
+  static get styles() {
+    const styleSheet = new CSSStyleSheet();
+    styleSheet.replaceSync(`\
+      :host #container {
+        transition-property: box-shadow;
+        transition-duration: 300ms;
+        transition-timing-function: linear;
+        box-shadow: 0 0 0 1px black;
+        padding: 10px;
+      }
+
+      :host([popped]) #container {
+        box-shadow: 0 0 10px 0 black;
+      }
+    `);
+    return [styleSheet];
+  }
+
   static get properties() {
     return {
       a: {
@@ -64,19 +82,6 @@ class TestElement extends XElement {
   static template(html) {
     return ({ changes }) => {
       return html`
-        <style>
-          :host #container {
-            transition-property: box-shadow;
-            transition-duration: 300ms;
-            transition-timing-function: linear;
-            box-shadow: 0 0 0 1px black;
-            padding: 10px;
-          }
-
-          :host([popped]) #container {
-            box-shadow: 0 0 10px 0 black;
-          }
-        </style>
         <div id="container">
           <div>Changes:</div>
           <ul>