[New]: Add no-duplicate-ids lint rule

Enforces that no `id` attributes are reused. This rule does a basic check to ensure that `id` attribute values are not the same. In the case of a JSX expression, it checks that no `id` attributes reuse the same expression.

__tests__/src/rules/no-duplicate-ids.js

@@ -0,0 +1,44 @@
+/**
+ * @fileoverview Disallow duplicate ids.
+ * @author Chris Ng
+ */
+
+// -----------------------------------------------------------------------------
+// Requirements
+// -----------------------------------------------------------------------------
+
+import { RuleTester } from 'eslint';
+import parserOptionsMapper from '../../__util__/parserOptionsMapper';
+import parsers from '../../__util__/helpers/parsers';
+import rule from '../../../src/rules/no-duplicate-ids';
+
+// -----------------------------------------------------------------------------
+// Tests
+// -----------------------------------------------------------------------------
+
+const ruleTester = new RuleTester();
+
+const expectedError = (idValue) => ({
+  message: `Duplicate ID "${idValue}" found. ID attribute values must be unique.`,
+  type: 'JSXOpeningElement',
+});
+
+const expectedJSXError = (idValue) => ({
+  message: `Duplicate ID "${idValue}" found. ID attribute JSX experssions must be unique.`,
+  type: 'JSXOpeningElement',
+});
+
+ruleTester.run('no-duplicate-ids', rule, {
+  valid: parsers.all([].concat(
+    { code: '<div><div id="chris"></div><div id="chris2"></div></div>' },
+    { code: '<div><div id={chris}></div><div id={chris2}></div></div>' },
+    { code: '<div><MyComponent id="chris" /><MyComponent id="chris2" /></div>' },
+    { code: '<div><div id="chris"></div><MyComponent id={chris} /></div>' },
+  )).map(parserOptionsMapper),
+  invalid: parsers.all([].concat(
+    { code: '<div><div id="chris"></div><div id="chris"></div></div>', errors: [expectedError('chris')] },
+    { code: '<div><div id={chris}></div><div id={chris}></div></div>', errors: [expectedJSXError('chris')] },
+    { code: '<div><MyComponent id="chris" /><MyComponent id="chris" /></div>', errors: [expectedError('chris')] },
+    { code: '<div><div id={chris}></div><MyComponent id={chris} /></div>', errors: [expectedJSXError('chris')] },
+  )).map(parserOptionsMapper),
+});

docs/rules/no-duplicate-ids.md

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+# jsx-a11y/no-duplicate-ids
+
+💼 This rule is enabled in the following configs: ☑️ `recommended`, 🔒 `strict`.
+
+<!-- end auto-generated rule header -->
+
+Enforces that no `id` attributes are reused. This rule does a basic check to ensure that `id` attribute values are not the same. In the case of a JSX expression, it checks that no `id` attributes reuse the same expression.
+
+## Rule details
+
+This rule takes no arguments.
+
+### Succeed
+
+```jsx
+<div id="chris"></div><div id="chris2"></div>
+<div id={chris}></div><div id={chris2}></div>
+<MyComponent id="chris" /><MyComponent id="chris2" />
+<div id="chris"></div><MyComponent id={chris} />
+```
+
+### Fail
+
+```jsx
+<div id="chris"></div><div id="chris"></div>
+<div id={chris}></div><div id={chris}></div>
+<MyComponent id="chris" /><MyComponent id="chris" />
+<MyComponent id={chris} /><div id={chris}></div>
+```
+
+## Accessibility guidelines
+- [WCAG 4.1.1](https://www.w3.org/WAI/WCAG21/Understanding/parsing.html)

src/index.js

@@ -29,6 +29,7 @@ module.exports = {
     'no-aria-hidden-on-focusable': require('./rules/no-aria-hidden-on-focusable'),
     'no-autofocus': require('./rules/no-autofocus'),
     'no-distracting-elements': require('./rules/no-distracting-elements'),
+    'no-duplicate-ids': require('./rules/no-duplicate-ids'),
     'no-interactive-element-to-noninteractive-role': require('./rules/no-interactive-element-to-noninteractive-role'),
     'no-noninteractive-element-interactions': require('./rules/no-noninteractive-element-interactions'),
     'no-noninteractive-element-to-interactive-role': require('./rules/no-noninteractive-element-to-interactive-role'),
@@ -116,6 +117,7 @@ module.exports = {
         'jsx-a11y/no-access-key': 'error',
         'jsx-a11y/no-autofocus': 'error',
         'jsx-a11y/no-distracting-elements': 'error',
+        'jsx-a11y/no-duplicate-ids': 'error',
         'jsx-a11y/no-interactive-element-to-noninteractive-role': [
           'error',
           {
@@ -273,6 +275,7 @@ module.exports = {
         'jsx-a11y/no-access-key': 'error',
         'jsx-a11y/no-autofocus': 'error',
         'jsx-a11y/no-distracting-elements': 'error',
+        'jsx-a11y/no-duplicate-ids': 'error',
         'jsx-a11y/no-interactive-element-to-noninteractive-role': 'error',
         'jsx-a11y/no-noninteractive-element-interactions': [
           'error',

src/rules/no-duplicate-ids.js

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+/**
+ * @fileoverview Disallow duplicate ids.
+ * @author Chris Ng
+ */
+
+// ----------------------------------------------------------------------------
+// Rule Definition
+// ----------------------------------------------------------------------------
+
+import { getProp, getPropValue } from 'jsx-ast-utils';
+import { generateObjSchema } from '../util/schemas';
+
+const schema = generateObjSchema();
+
+export default {
+  meta: {
+    docs: {
+      url: 'https://github.com/jsx-eslint/eslint-plugin-jsx-a11y/tree/HEAD/docs/rules/no-duplicate-ids.md',
+      description: 'Disallow duplicate ids.',
+    },
+    schema: [schema],
+  },
+
+  create(context) {
+    const idsUsedSet = new Set();
+    const jsxExperissionIDsUsedSet = new Set();
+
+    return {
+      JSXOpeningElement(node) {
+        const { attributes } = node;
+        const idProp = getProp(attributes, 'id');
+        const idValue = getPropValue(idProp);
+
+        // Special case if id is assigned using JSXExpressionContainer
+        if (idProp && idProp.type === 'JSXAttribute' && idProp.value.type === 'JSXExpressionContainer') {
+          if (jsxExperissionIDsUsedSet.has(idValue)) {
+            context.report({
+              node,
+              message: `Duplicate ID "${idValue}" found. ID attribute JSX experssions must be unique.`,
+            });
+          } else {
+            jsxExperissionIDsUsedSet.add(idValue);
+          }
+        } else if (idsUsedSet.has(idValue)) {
+          context.report({
+            node,
+            message: `Duplicate ID "${idValue}" found. ID attribute values must be unique.`,
+          });
+        } else {
+          idsUsedSet.add(idValue);
+        }
+      },
+    };
+  },
+};