typescript-eslint · mohsen1 · Feb 20, 2019 · Mar 8, 2019 · Mar 8, 2019 · Jan 19, 2020
diff --git a/packages/eslint-plugin/README.md b/packages/eslint-plugin/README.md
@@ -102,6 +102,7 @@ Pro Tip: For larger codebases you may want to consider splitting our linting int
 | [`@typescript-eslint/ban-types`](./docs/rules/ban-types.md)                                                     | Bans specific types from being used                                                                                                                 | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/consistent-type-assertions`](./docs/rules/consistent-type-assertions.md)                   | Enforces consistent usage of type assertions                                                                                                        | :heavy_check_mark: |          |                   |
 | [`@typescript-eslint/consistent-type-definitions`](./docs/rules/consistent-type-definitions.md)                 | Consistent with type definition either `interface` or `type`                                                                                        |                    | :wrench: |                   |
+| [`@typescript-eslint/enum-const-style`](./docs/rules/enum-const-style.md)                                       | Enforce const enum style                                                                                                                            |                    |          |                   |
 | [`@typescript-eslint/explicit-function-return-type`](./docs/rules/explicit-function-return-type.md)             | Require explicit return types on functions and class methods                                                                                        | :heavy_check_mark: |          |                   |
 | [`@typescript-eslint/explicit-member-accessibility`](./docs/rules/explicit-member-accessibility.md)             | Require explicit accessibility modifiers on class properties and methods                                                                            |                    |          |                   |
 | [`@typescript-eslint/explicit-module-boundary-types`](./docs/rules/explicit-module-boundary-types.md)           | Require explicit return and argument types on exported functions' and classes' public class methods                                                 |                    |          |                   |

diff --git a/packages/eslint-plugin/docs/rules/enum-const-style.md b/packages/eslint-plugin/docs/rules/enum-const-style.md
@@ -0,0 +1,61 @@
+# Enforce const enum style (`enum-const-style`)
+
+This rule enforces consistent usage of `const enum`.
+
+## Rule Details
+
+This rule aims to standardize usage of const enums.
+
+## Options
+
+### Default config: `never`
+
+```JSON
+{
+  "enum-const-style": ["error", "never"]
+}
+```
+
+Examples of **incorrect** code for this rule with `never` config:
+
+```ts
+enum Foo {
+  ONE,
+  TWO,
+}
+```
+
+Examples of **correct** code for this rule with `never` config:
+
+```ts
+const enum Foo {
+  ONE,
+  TWO,
+}
+```
+
+### `always` config
+
+Only const enums are allowed
+
+Examples of **incorrect** code for this rule with `always` config:
+
+```ts
+enum const Foo {
-enum const Foo {
+const enum Foo {
-enum const Foo {
+const enum Foo {
+  ONE,
+  TWO,
+}
+```
+
+Examples of **correct** code for this rule with `always` config:
+
+```ts
+const Foo {
+  ONE,
+  TWO,
+}
+```
+
+## When Not To Use It
+
+If you don't want to regulate usage of `const enum`s.
diff --git a/packages/eslint-plugin/src/configs/all.json b/packages/eslint-plugin/src/configs/all.json
@@ -12,6 +12,7 @@
     "@typescript-eslint/consistent-type-definitions": "error",
     "default-param-last": "off",
     "@typescript-eslint/default-param-last": "error",
+    "@typescript-eslint/enum-const-style": "error",
     "@typescript-eslint/explicit-function-return-type": "error",
     "@typescript-eslint/explicit-member-accessibility": "error",
     "@typescript-eslint/explicit-module-boundary-types": "error",

diff --git a/packages/eslint-plugin/src/rules/enum-const-style.ts b/packages/eslint-plugin/src/rules/enum-const-style.ts
@@ -0,0 +1,44 @@
+import { TSESTree } from '@typescript-eslint/experimental-utils';
+import * as util from '../util';
+
+type Messages = 'noNonConstEnums' | 'noConstEnums';
+type Options = ['always' | 'never'];
+
+export default util.createRule<Options, Messages>({
+  name: 'enum-const-style',
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'Enforce const enum style',
+      category: 'Stylistic Issues',
+      recommended: false,
+    },
+    messages: {
+      noNonConstEnums: 'enums are forbidden. Use const enums',
+      noConstEnums: 'const enums are forbidden. Use enum',
+    },
+    schema: [
+      {
+        enum: ['always', 'never'],
+      },
+    ],
+  },
+  defaultOptions: ['never'],
+  create(context, [options]) {
+    return {
+      TSEnumDeclaration(node: TSESTree.TSEnumDeclaration): void {
+        if (options === 'always' && !node.const) {
+          context.report({
+            node,
+            messageId: 'noNonConstEnums',
+          });
+        } else if (options === 'never' && node.const) {
+          context.report({
+            node,
+            messageId: 'noConstEnums',
+          });
+        }
+      },
+    };
+  },
+});
diff --git a/packages/eslint-plugin/src/rules/index.ts b/packages/eslint-plugin/src/rules/index.ts
@@ -9,6 +9,7 @@ import classNameCasing from './class-name-casing';
 import consistentTypeAssertions from './consistent-type-assertions';
 import consistentTypeDefinitions from './consistent-type-definitions';
 import defaultParamLast from './default-param-last';
+import enumConstStyle from './enum-const-style';
 import explicitFunctionReturnType from './explicit-function-return-type';
 import explicitMemberAccessibility from './explicit-member-accessibility';
 import explicitModuleBoundaryTypes from './explicit-module-boundary-types';
@@ -92,6 +93,7 @@ export default {
   'consistent-type-assertions': consistentTypeAssertions,
   'consistent-type-definitions': consistentTypeDefinitions,
   'default-param-last': defaultParamLast,
+  'enum-const-style': enumConstStyle,
   'explicit-function-return-type': explicitFunctionReturnType,
   'explicit-member-accessibility': explicitMemberAccessibility,
   'explicit-module-boundary-types': explicitModuleBoundaryTypes,

diff --git a/packages/eslint-plugin/tests/rules/enum-const-style.test.ts b/packages/eslint-plugin/tests/rules/enum-const-style.test.ts
@@ -0,0 +1,81 @@
+import rule from '../../src/rules/enum-const-style';
+import { RuleTester } from '../RuleTester';
+
+const ruleTester = new RuleTester({
+  parser: '@typescript-eslint/parser',
+});
+
+ruleTester.run('enum-style', rule, {
+  valid: [
+    'enum Foo {}',
+    'enum Foo { FOO }',
+    'enum Foo { FOO = 1, BAR = 2 }',
+    'enum Foo { FOO = "FOO", BAR = "BAR" }',
+    {
+      code: 'const enum Foo {}',
+      options: ['always'],
+    },
+    {
+      code: 'const enum Foo { FOO }',
+      options: ['always'],
+    },
+    {
+      code: 'const enum Foo { FOO = 1, BAR = 2 }',
+      options: ['always'],
+    },
+    {
+      code: 'const enum Foo { FOO = "FOO", BAR = "BAR" }',
+      options: ['always'],
+    },
+    {
+      code: 'enum Foo {}',
+      options: ['never'],
+    },
+    {
+      code: 'enum Foo { FOO }',
+      options: ['never'],
+    },
+    {
+      code: 'enum Foo { FOO = 1, BAR = 2 }',
+      options: ['never'],
+    },
+    {
+      code: 'enum Foo { FOO = "FOO", BAR = "BAR" }',
+      options: ['never'],
+    },
+  ],
+  invalid: [
+    {
+      code: 'const enum Foo {}',
+      errors: [
+        {
+          messageId: 'noConstEnums',
+          line: 1,
+          column: 1,
+        },
+      ],
+    },
+    {
+      code: 'const enum Foo {}',
+      errors: [
+        {
+          messageId: 'noConstEnums',
+          line: 1,
+          column: 1,
+        },
+      ],
+      options: ['never'],
+    },
+    {
+      code: 'enum Foo {}',
+      errors: [
+        {
+          messageId: 'noNonConstEnums',
+          line: 1,
+          column: 1,
+        },
+      ],
+      options: ['always'],
+    },
+  ],
+});