Use at() instead of direct access

eslint-plugin-expensify/CONST.js

@@ -28,5 +28,7 @@ module.exports = {
         MUST_USE_VARIABLE_FOR_ASSIGNMENT: '{{key}} must be assigned as a variable instead of direct assignment.',
         NO_DEFAULT_PROPS: 'defaultProps should not be used in function components. Use default Arguments instead.',
         USE_PERIODS_ERROR_MESSAGES: 'Use periods at the end of error messages.',
+        USE_DOUBLE_NEGATION_INSTEAD_OF_BOOLEAN: 'Use !! instead of Boolean().',
+        PREFER_AT: 'Use the .at() method for array element access',
     },
 };

eslint-plugin-expensify/prefer-at.js

@@ -0,0 +1,26 @@
+const message = require('./CONST').MESSAGE.PREFER_AT;
+
+module.exports = {
+    meta: {
+        fixable: 'code',
+    },
+
+    create(context) {
+        return {
+            MemberExpression(node) {
+                // Check if we are accessing an array element directly
+                if (node.object.type === 'Identifier' && node.property.type === 'Literal' && typeof node.property.value === 'number') {
+                    context.report({
+                        node,
+                        message,
+                        fix(fixer) {
+                            const arrayName = node.object.name;
+                            const indexValue = node.property.value;
+                            return fixer.replaceText(node, `${arrayName}.at(${indexValue})`);
+                        },
+                    });
+                }
+            },
+        };
+    },
+};

eslint-plugin-expensify/tests/prefer-at.test.js

@@ -0,0 +1,37 @@
+const RuleTester = require('eslint').RuleTester;
+const rule = require('../prefer-at');
+const message = require('../CONST').MESSAGE.PREFER_AT;
+
+const ruleTester = new RuleTester({
+    parserOptions: {
+        ecmaVersion: 6,
+        sourceType: 'module',
+    },
+});
+
+ruleTester.run('prefer-at', rule, {
+    valid: [
+        {
+            code: 'example.at(0)',
+        },
+        {
+            code: 'test.at(1)',
+        },
+    ],
+    invalid: [
+        {
+            code: 'example[0]',
+            output: 'example.at(0)',
+            errors: [{
+                message,
+            }],
+        },
+        {
+            code: 'test[1]',
+            output: 'test.at(1)',
+            errors: [{
+                message,
+            }],
+        },
+    ],
+});

rules/expensify.js

@@ -15,6 +15,8 @@ module.exports = {
         'rulesdir/no-call-actions-from-actions': 'error',
         'rulesdir/no-api-side-effects-method': 'error',
         'rulesdir/prefer-localization': 'error',
+        'rulesdir/use-double-negation-instead-of-boolean': 'error',
+        'rulesdir/prefer-at': 'error',
         'no-restricted-imports': ['error', {
             paths: [{
                 name: 'react-native',
@@ -27,4 +29,4 @@ module.exports = {
             }],
         }],
     },
-};
+};