no-unknown-property: add download property support for a and `a…

…rea`

fixes #3393

CHANGELOG.md

@@ -4,6 +4,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 This change log adheres to standards from [Keep a CHANGELOG](https://keepachangelog.com).
 
 ## Unreleased
+* [`no-unknown-property`]: add `download` property support for `a` and `area` 
 
 ### Fixed
 * [`no-unknown-property`]: avoid warning on `fbt` nodes entirely ([#3391][] @ljharb)

lib/rules/no-unknown-property.js

@@ -30,6 +30,8 @@ const ATTRIBUTE_TAGS_MAP = {
   checked: ['input'],
   // image is required for SVG support, all other tags are HTML.
   crossOrigin: ['script', 'img', 'video', 'audio', 'link', 'image'],
+  // https://html.spec.whatwg.org/multipage/links.html#downloading-resources
+  download: ['a', 'area'],
   fill: [ // https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/fill
     // Fill color
     'altGlyph',

tests/lib/rules/no-unknown-property.js

@@ -44,7 +44,8 @@ ruleTester.run('no-unknown-property', rule, {
     // Some HTML/DOM elements with common attributes should work
     { code: '<div className="bar"></div>;' },
     { code: '<div onMouseDown={this._onMouseDown}></div>;' },
-    { code: '<a href="someLink">Read more</a>' },
+    { code: '<a href="someLink" download="foo">Read more</a>' },
+    { code: '<area download="foo" />' },
     { code: '<img src="cat_keyboard.jpeg" alt="A cat sleeping on a keyboard" />' },
     { code: '<input type="password" required />' },
     { code: '<input ref={this.input} type="radio" />' },
@@ -466,5 +467,18 @@ ruleTester.run('no-unknown-property', rule, {
         },
       ],
     },
+    {
+      code: '<div download="foo" />',
+      errors: [
+        {
+          messageId: 'invalidPropOnTag',
+          data: {
+            name: 'download',
+            tagName: 'div',
+            allowedTags: 'a, area',
+          },
+        },
+      ],
+    },
   ]),
 });