Add check to use periods at the end of error messages

eslint-plugin-expensify/CONST.js

@@ -28,5 +28,6 @@ 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.',
         AVOID_ANONYMOUS_FUNCTIONS: 'Prefer named functions.',
+        USE_PERIODS_ERROR_MESSAGES: 'Use periods at the end of error messages.',
     },
 };

eslint-plugin-expensify/tests/use-periods-error-messages.test.js

@@ -0,0 +1,38 @@
+const RuleTester = require('eslint').RuleTester;
+const rule = require('../use-periods-for-error-messages');
+const message = require('../CONST').MESSAGE.USE_PERIODS_ERROR_MESSAGES;
+
+const ruleTester = new RuleTester({
+    parserOptions: {
+        ecmaVersion: 6,
+        sourceType: 'module',
+    },
+});
+
+const goodExample = `
+error: {
+    testMessage: 'This is a test message.'
+}
+`;
+
+const badExample = `
+error: {
+    testMessage: 'This is a test message'
+}
+`;
+
+ruleTester.run('use-periods-for-error-messages', rule, {
+    valid: [
+        {
+            code: goodExample,
+        },
+    ],
+    invalid: [
+        {
+            code: badExample,
+            errors: [{
+                message,
+            }],
+        },
+    ],
+});

eslint-plugin-expensify/use-periods-for-error-messages.js

@@ -0,0 +1,30 @@
+require('lodash/get');
+const message = require('./CONST').MESSAGE.USE_PERIODS_ERROR_MESSAGES;
+
+module.exports = {
+    create(context) {
+        return {
+            Property(node) {
+                if (!node.key || node.key.name !== 'error' || !node.value || node.value.type !== 'ObjectExpression') {
+                    return;
+                }
+                node.value.properties.forEach((property) => {
+                    if (!property.value || property.value.type !== 'Literal' || typeof property.value.value !== 'string') {
+                        return;
+                    }
+                    const errorMessage = property.value.value;
+                    if (!errorMessage.endsWith('.')) {
+                        context.report({
+                            node: property,
+                            message,
+                            fix: function (fixer) {
+                                const fixedMessage = `${errorMessage}.`;
+                                return fixer.replaceText(property.value, `'${fixedMessage}'`);
+                            }
+                        });
+                    }
+                });
+            },
+        };
+    },
+};