error for I prefixed interface names

Summary: {gif:kosnw403}

Reviewed By: mweststrate

Differential Revision: D33845782

fbshipit-source-id: 2b9bd70e3b2d930e8f4cd8fe7976ac76f43b2496

desktop/.eslintrc.js

@@ -145,6 +145,7 @@ module.exports = {
     'flipper/no-electron-remote-imports': [1],
     'flipper/no-console-error-without-context': [2],
     'flipper/no-ts-file-extension': 1,
+    'flipper/no-i-prefix-interfaces': 2,
     'communist-spelling/communist-spelling': [1, {allow: ['cancelled']}],
 
     // promise rules, see https://github.com/xjamundx/eslint-plugin-promise for details on each of them

desktop/eslint-plugin-flipper/src/index.ts

@@ -19,6 +19,9 @@ import noConsoleErrorWithoutContext, {
 import noTsFileExtension, {
   RULE_NAME as noTsFileExtensionRuleName,
 } from './rules/noTsFileExtension';
+import noIPrefixInterfaces, {
+  RULE_NAME as noIPrefixInterfacesRuleName,
+} from './rules/noIPrefixInterfaces';
 
 module.exports = {
   rules: {
@@ -26,5 +29,6 @@ module.exports = {
     [noElectronRemoteImportsRuleName]: noElectronRemoteImports,
     [noConsoleErrorWithoutContextRuleName]: noConsoleErrorWithoutContext,
     [noTsFileExtensionRuleName]: noTsFileExtension,
+    [noIPrefixInterfacesRuleName]: noIPrefixInterfaces,
   },
 };

desktop/eslint-plugin-flipper/src/rules/__tests__/noIPrefixInterfaces.node.ts

@@ -0,0 +1,39 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import {TSESLint} from '@typescript-eslint/experimental-utils';
+import rule, {RULE_NAME} from '../noIPrefixInterfaces';
+
+const tester = new TSESLint.RuleTester({
+  parser: require.resolve('@typescript-eslint/parser'),
+  parserOptions: {
+    sourceType: 'module',
+    ecmaVersion: 2020,
+  },
+});
+
+tester.run(RULE_NAME, rule, {
+  valid: [
+    {
+      code: `interface Icon {name: string}`,
+      filename: __filename,
+    },
+    {
+      code: `interface IOSDevice {version: string}`,
+      filename: __filename,
+    },
+  ],
+  invalid: [
+    {
+      code: `interface IDevice {version: string;}`,
+      filename: __filename,
+      errors: [{messageId: 'noTsInterfacePrefixI'}],
+    },
+  ],
+});

desktop/eslint-plugin-flipper/src/rules/noIPrefixInterfaces.ts

@@ -0,0 +1,54 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import {createESLintRule} from '../utils/createEslintRule';
+
+type Options = [];
+
+export type MessageIds = 'noTsInterfacePrefixI';
+export const RULE_NAME = 'no-i-prefix-interfaces';
+
+export default createESLintRule<Options, MessageIds>({
+  name: RULE_NAME,
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'Avoid prefixing TS interfaces with "I"',
+      recommended: 'error',
+    },
+    schema: [],
+    messages: {
+      noTsInterfacePrefixI: 'Do not prefix interfaces with "I"',
+    },
+  },
+  defaultOptions: [],
+  create(context) {
+    return {
+      TSInterfaceDeclaration(node) {
+        const [l1, l2, l3] = node.id.name;
+        if (
+          l1 === 'I' &&
+          isLetter(l2) &&
+          l2 === l2.toUpperCase() &&
+          isLetter(l3) &&
+          l3 === l3.toLowerCase()
+        ) {
+          context.report({
+            node: node.id,
+            messageId: 'noTsInterfacePrefixI',
+          });
+        }
+      },
+    };
+  },
+});
+
+function isLetter(x: string | undefined): boolean {
+  return typeof x === 'string' && /^[a-z]$/i.test(x);
+}

docs/extending/dev-setup.mdx

@@ -159,7 +159,6 @@ To start Flipper against a specific OnDemand instance, set FB_ONDEMAND flag, e.g
 
 ## Guidelines for writing TypeScript
 * Prefer `type` for React props and state over interfaces
-* Don’t prefix interfaces with `I`
 * Install 3rd party type definitions as dev dependency (e.g. `yarn add @types/lodash --dev`)
 
 ## Submitting a diff / PR