[Fix] no-unknown-property: React lowercases data- attrs

Fixes #3395

CHANGELOG.md

@@ -15,6 +15,7 @@ This change log adheres to standards from [Keep a CHANGELOG](https://keepachange
 * [`no-unknown-property`]: Mark onLoad/onError as supported on iframes ([#3398][] @maiis, [#3406][] @akx)
 * [`no-unknown-property`]: allow `imageSrcSet` and `imageSizes` attributes on `<link>` ([#3407][] @terrymun)
 * [`no-unknown-property`]: add `border`; `focusable` on `<svg>` ([#3404][] [#3404][] @ljharb)
+* [`no-unknown-property`]: React lowercases `data-` attrs ([#3395][] @ljharb)
 
 [#3407]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3407
 [#3406]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3406
@@ -24,6 +25,7 @@ This change log adheres to standards from [Keep a CHANGELOG](https://keepachange
 [#3398]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3398
 [#3397]: https://github.com/jsx-eslint/eslint-plugin-react/issues/3397
 [#3396]: https://github.com/jsx-eslint/eslint-plugin-react/issues/3396
+[#3395]: https://github.com/jsx-eslint/eslint-plugin-react/issues/3395
 [#3394]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3394
 [#3391]: https://github.com/jsx-eslint/eslint-plugin-react/issues/3391
 

lib/rules/no-unknown-property.js

@@ -388,15 +388,15 @@ function isValidHTMLTagInJSX(childNode) {
 
 /**
  * Checks if an attribute name is a valid `data-*` attribute:
- * if the name starts with "data-" and has some lowcase (a to z) words that can contain numbers, separated but hyphens (-)
- * (which is also called "kebab case" or "dash case"), then the attribute is valid data attribute.
+ * if the name starts with "data-" and has alphanumeric words (browsers require lowercase, but React and TS lowercase them),
+ * not start with any casing of "xml", and separated by hyphens (-) (which is also called "kebab case" or "dash case"),
+ * then the attribute is a valid data attribute.
  *
  * @param {String} name - Attribute name to be tested
  * @returns {boolean} Result
  */
 function isValidDataAttribute(name) {
-  const dataAttrConvention = /^data(-[a-z1-9]*)*$/;
-  return !!dataAttrConvention.test(name);
+  return /^data(-[^:]*)*$/.test(name) && !/^data-xml/i.test(name);
 }
 
 /**

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

@@ -91,6 +91,7 @@ ruleTester.run('no-unknown-property', rule, {
     { code: '<div data-parent="parent"></div>;' },
     { code: '<div data-index-number="1234"></div>;' },
     { code: '<div data-e2e-id="5678"></div>;' },
+    { code: '<div data-testID="bar" data-under_sCoRe="bar" />;' },
     // Ignoring should work
     {
       code: '<div class="bar"></div>;',
@@ -511,5 +512,16 @@ ruleTester.run('no-unknown-property', rule, {
         },
       ],
     },
+    {
+      code: '<div data-xml-anything="invalid" />',
+      errors: [
+        {
+          messageId: 'unknownProp',
+          data: {
+            name: 'data-xml-anything',
+          },
+        },
+      ],
+    },
   ]),
 });