feat(eslint-plugin): add extension rule lines-between-class-members (…

…#1684)

packages/eslint-plugin/README.md

@@ -187,6 +187,7 @@ In these cases, we create what we call an extension rule; a rule within our plug
 | [`@typescript-eslint/indent`](./docs/rules/indent.md)                                           | Enforce consistent indentation                                                 |                    | :wrench: |                   |
 | [`@typescript-eslint/init-declarations`](./docs/rules/init-declarations.md)                     | require or disallow initialization in variable declarations                    |                    |          |                   |
 | [`@typescript-eslint/keyword-spacing`](./docs/rules/keyword-spacing.md)                         | Enforce consistent spacing before and after keywords                           |                    | :wrench: |                   |
+| [`@typescript-eslint/lines-between-class-members`](./docs/rules/lines-between-class-members.md) | Require or disallow an empty line between class members                        |                    | :wrench: |                   |
 | [`@typescript-eslint/no-array-constructor`](./docs/rules/no-array-constructor.md)               | Disallow generic `Array` constructors                                          | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/no-dupe-class-members`](./docs/rules/no-dupe-class-members.md)             | Disallow duplicate class members                                               |                    |          |                   |
 | [`@typescript-eslint/no-empty-function`](./docs/rules/no-empty-function.md)                     | Disallow empty functions                                                       | :heavy_check_mark: |          |                   |

packages/eslint-plugin/docs/rules/lines-between-class-members.md

@@ -0,0 +1,73 @@
+# Require or disallow an empty line between class members (`lines-between-class-members`)
+
+This rule improves readability by enforcing lines between class members. It will not check empty lines before the first member and after the last member. This rule require or disallow an empty line between class members.
+
+## Rule Details
+
+This rule extends the base [`eslint/lines-between-class-members`](https://eslint.org/docs/rules/lines-between-class-members) rule.
+It adds support for ignoring overload methods in a class.
+
+See the [ESLint documentation](https://eslint.org/docs/rules/lines-between-class-members) for more details on the `lines-between-class-members` rule.
+
+## Rule Changes
+
+```cjson
+{
+  // note you must disable the base rule as it can report incorrect errors
+  "lines-between-class-members": "off",
+  "@typescript-eslint/lines-between-class-members": ["error"]
+}
+```
+
+In addition to the options supported by the `lines-between-class-members` rule in ESLint core, the rule adds the following options:
+
+## Options
+
+This rule has a string option and an object option.
+
+- Object option:
+
+  - `"exceptAfterOverload": true` (default) - Skip checking empty lines after overload class members
+  - `"exceptAfterOverload": false` - **do not** skip checking empty lines after overload class members
+
+- [See the other options allowed](https://github.com/eslint/eslint/blob/master/docs/rules/lines-between-class-members.md#options)
+
+### `exceptAfterOverload: true`
+
+Examples of **correct** code for the `{ "exceptAfterOverload": true }` option:
+
+```ts
+/*eslint @typescript-eslint/lines-between-class-members: ["error", "always", { "exceptAfterOverload": true }]*/
+
+class foo {
+  bar(a: string): void;
+  bar(a: string, b: string): void;
+  bar(a: string, b: string) {}
+
+  baz() {}
+
+  qux() {}
+}
+```
+
+### `exceptAfterOverload: false`
+
+Examples of **correct** code for the `{ "exceptAfterOverload": false }` option:
+
+```ts
+/*eslint @typescript-eslint/lines-between-class-members: ["error", "always", { "exceptAfterOverload": false }]*/
+
+class foo {
+  bar(a: string): void;
+
+  bar(a: string, b: string): void;
+
+  bar(a: string, b: string) {}
+
+  baz() {}
+
+  qux() {}
+}
+```
+
+<sup>Taken with ❤️ [from ESLint core](https://github.com/eslint/eslint/blob/master/docs/rules/lines-between-class-members.md)</sup>

packages/eslint-plugin/src/configs/all.json

@@ -24,6 +24,8 @@
     "@typescript-eslint/func-call-spacing": "error",
     "indent": "off",
     "@typescript-eslint/indent": "error",
+    "lines-between-class-members": "off",
+    "@typescript-eslint/lines-between-class-members": "error",
     "init-declarations": "off",
     "@typescript-eslint/init-declarations": "error",
     "keyword-spacing": "off",

packages/eslint-plugin/src/rules/index.ts

@@ -100,6 +100,7 @@ import typeAnnotationSpacing from './type-annotation-spacing';
 import typedef from './typedef';
 import unboundMethod from './unbound-method';
 import unifiedSignatures from './unified-signatures';
+import linesBetweenClassMembers from './lines-between-class-members';
 
 export default {
   'adjacent-overload-signatures': adjacentOverloadSignatures,
@@ -204,4 +205,5 @@ export default {
   typedef: typedef,
   'unbound-method': unboundMethod,
   'unified-signatures': unifiedSignatures,
+  'lines-between-class-members': linesBetweenClassMembers,
 };

packages/eslint-plugin/src/rules/lines-between-class-members.ts

@@ -0,0 +1,66 @@
+import {
+  AST_NODE_TYPES,
+  TSESTree,
+} from '@typescript-eslint/experimental-utils';
+import baseRule from 'eslint/lib/rules/lines-between-class-members';
+import * as util from '../util';
+
+type Options = util.InferOptionsTypeFromRule<typeof baseRule>;
+type MessageIds = util.InferMessageIdsTypeFromRule<typeof baseRule>;
+
+const schema = util.deepMerge(
+  { ...baseRule.meta.schema },
+  {
+    1: {
+      exceptAfterOverload: {
+        type: 'booleean',
+        default: true,
+      },
+    },
+  },
+);
+
+export default util.createRule<Options, MessageIds>({
+  name: 'lines-between-class-members',
+  meta: {
+    type: 'layout',
+    docs: {
+      description: 'Require or disallow an empty line between class members',
+      category: 'Stylistic Issues',
+      recommended: false,
+      extendsBaseRule: true,
+    },
+    fixable: 'whitespace',
+    schema,
+    messages: baseRule.meta.messages,
+  },
+  defaultOptions: [
+    'always',
+    {
+      exceptAfterOverload: true,
+      exceptAfterSingleLine: false,
+    },
+  ],
+  create(context, options) {
+    const rules = baseRule.create(context);
+    const exceptAfterOverload =
+      options[1]?.exceptAfterOverload && options[0] === 'always';
+
+    function isOverload(node: TSESTree.Node): boolean {
+      return (
+        node.type === AST_NODE_TYPES.MethodDefinition &&
+        node.value.type === AST_NODE_TYPES.TSEmptyBodyFunctionExpression
+      );
+    }
+
+    return {
+      ClassBody(node): void {
+        const body = exceptAfterOverload
+          ? node.body.filter(node => !isOverload(node))
+          : node.body;
+
+        rules.ClassBody({ ...node, body });
+      },
+    };
+  },
+});