[New] no-unknown-property: add requireDataLowercase option

Fixes #3643

CHANGELOG.md

@@ -8,6 +8,7 @@ This change log adheres to standards from [Keep a CHANGELOG](https://keepachange
 ### Added
 * [`sort-prop-types`]: give errors on TS types ([#3615][] @akulsr0)
 * [`no-invalid-html-attribute`]: add support for `apple-touch-startup-image` `rel` attributes in `link` tags ([#3638][] @thomashockaday)
+* [`no-unknown-property`]: add requireDataLowercase option ([#3645][] @HermanBilous)
 
 ### Fixed
 * [`jsx-no-leaked-render`]: preserve RHS parens for multiline jsx elements while fixing ([#3623][] @akulsr0)
@@ -20,6 +21,7 @@ This change log adheres to standards from [Keep a CHANGELOG](https://keepachange
 * [Refactor] [`function-component-definition`]: exit early if no type params ([#3634][] @HenryBrown0)
 * [Refactor] [`jsx-props-no-multi-spaces`]: extract type parameters to var ([#3634][] @HenryBrown0)
 
+[#3645]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3645
 [#3638]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3638
 [#3634]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3634
 [#3633]: https://github.com/jsx-eslint/eslint-plugin-react/issues/3633

docs/rules/no-unknown-property.md

@@ -51,12 +51,13 @@ var AtomPanel = <atom-panel class="foo"></atom-panel>;
 
 ```js
 ...
-"react/no-unknown-property": [<enabled>, { ignore: <ignore> }]
+"react/no-unknown-property": [<enabled>, { ignore: <ignore>, requireDataLowercase: <requireDataLowercase> }]
 ...
 ```
 
 - `enabled`: for enabling the rule. 0=off, 1=warn, 2=error. Defaults to 0.
 - `ignore`: optional array of property and attribute names to ignore during validation.
+- `requireDataLowercase`: optional (default: `false`), require data-\* attributes to contain only lowercase characters. React will issue a warning when data-\* attributes contain uppercase characters. In order to catch such attributes, set the `requireDataLowercase` option to `true`.
 
 If you are using a library that passes something as a prop to JSX elements, it is recommended to add those props to the ignored properties.
 

lib/rules/no-unknown-property.js

@@ -16,6 +16,7 @@ const report = require('../util/report');
 
 const DEFAULTS = {
   ignore: [],
+  requireDataLowercase: false,
 };
 
 const DOM_ATTRIBUTE_NAMES = {
@@ -429,6 +430,16 @@ function isValidDataAttribute(name) {
   return /^data(-[^:]*)*$/.test(name) && !/^data-xml/i.test(name);
 }
 
+/**
+ * Checks if an attribute name has at least one uppercase characters
+ *
+ * @param {String} name
+ * @returns {boolean} Result
+ */
+function hasUpperCaseCharacter(name) {
+  return name.toLowerCase() !== name;
+}
+
 /**
  * Checks if an attribute name is a standard aria attribute by compering it to a list
  * of standard aria property names
@@ -493,6 +504,7 @@ const messages = {
   invalidPropOnTag: 'Invalid property \'{{name}}\' found on tag \'{{tagName}}\', but it is only allowed on: {{allowedTags}}',
   unknownPropWithStandardName: 'Unknown property \'{{name}}\' found, use \'{{standardName}}\' instead',
   unknownProp: 'Unknown property \'{{name}}\' found',
+  dataLowercaseRequired: 'React does not recognize data-* props with uppercase characters on a DOM element. Found \'{{name}}\', use \'{{lowerCaseName}}\' instead',
 };
 
 module.exports = {
@@ -516,6 +528,10 @@ module.exports = {
             type: 'string',
           },
         },
+        requireDataLowercase: {
+          type: 'boolean',
+          default: false,
+        },
       },
       additionalProperties: false,
     }],
@@ -526,6 +542,12 @@ module.exports = {
       return (context.options[0] && context.options[0].ignore) || DEFAULTS.ignore;
     }
 
+    function getRequireDataLowercase() {
+      return (context.options[0] && typeof context.options[0].requireDataLowercase !== 'undefined')
+        ? !!context.options[0].requireDataLowercase
+        : DEFAULTS.requireDataLowercase;
+    }
+
     return {
       JSXAttribute(node) {
         const ignoreNames = getIgnoreConfig();
@@ -540,7 +562,19 @@ module.exports = {
           return;
         }
 
-        if (isValidDataAttribute(name)) { return; }
+        if (isValidDataAttribute(name)) {
+          if (getRequireDataLowercase() && hasUpperCaseCharacter(name)) {
+            report(context, messages.dataLowercaseRequired, 'dataLowercaseRequired', {
+              node,
+              data: {
+                name: actualName,
+                lowerCaseName: actualName.toLowerCase(),
+              },
+            });
+          }
+
+          return;
+        }
 
         if (isValidAriaAttribute(name)) { return; }
 

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

@@ -99,6 +99,10 @@ ruleTester.run('no-unknown-property', rule, {
     { code: '<div data-index-number="1234"></div>;' },
     { code: '<div data-e2e-id="5678"></div>;' },
     { code: '<div data-testID="bar" data-under_sCoRe="bar" />;' },
+    {
+      code: '<div data-testID="bar" data-under_sCoRe="bar" />;',
+      options: [{ requireDataLowercase: false }],
+    },
     // Ignoring should work
     {
       code: '<div class="bar"></div>;',
@@ -573,6 +577,26 @@ ruleTester.run('no-unknown-property', rule, {
         },
       ],
     },
+    {
+      code: '<div data-testID="bar" data-under_sCoRe="bar" />;',
+      errors: [
+        {
+          messageId: 'dataLowercaseRequired',
+          data: {
+            name: 'data-testID',
+            lowerCaseName: 'data-testid',
+          },
+        },
+        {
+          messageId: 'dataLowercaseRequired',
+          data: {
+            name: 'data-under_sCoRe',
+            lowerCaseName: 'data-under_score',
+          },
+        },
+      ],
+      options: [{ requireDataLowercase: true }],
+    },
     {
       code: '<div abbr="abbr" />',
       errors: [