feat(eslint-plugin): new extended rule 'no-invalid-this' (#1823)

Co-Authored-By: Brad Zacher <brad.zacher@gmail.com>

packages/eslint-plugin/README.md

@@ -192,6 +192,7 @@ In these cases, we create what we call an extension rule; a rule within our plug
 | [`@typescript-eslint/no-empty-function`](./docs/rules/no-empty-function.md)                     | Disallow empty functions                                                       | :heavy_check_mark: |          |                   |
 | [`@typescript-eslint/no-extra-parens`](./docs/rules/no-extra-parens.md)                         | Disallow unnecessary parentheses                                               |                    | :wrench: |                   |
 | [`@typescript-eslint/no-extra-semi`](./docs/rules/no-extra-semi.md)                             | Disallow unnecessary semicolons                                                |                    | :wrench: |                   |
+| [`@typescript-eslint/no-invalid-this`](./docs/rules/no-invalid-this.md)                         | disallow `this` keywords outside of classes or class-like objects              |                    |          |                   |
 | [`@typescript-eslint/no-magic-numbers`](./docs/rules/no-magic-numbers.md)                       | Disallow magic numbers                                                         |                    |          |                   |
 | [`@typescript-eslint/no-unused-expressions`](./docs/rules/no-unused-expressions.md)             | Disallow unused expressions                                                    |                    |          |                   |
 | [`@typescript-eslint/no-unused-vars`](./docs/rules/no-unused-vars.md)                           | Disallow unused variables                                                      | :heavy_check_mark: |          |                   |

packages/eslint-plugin/docs/rules/no-invalid-this.md

@@ -0,0 +1,26 @@
+# disallow `this` keywords outside of classes or class-like objects (`no-invalid-this`)
+
+## Rule Details
+
+This rule extends the base [`eslint/no-invalid-this`](https://eslint.org/docs/rules/no-invalid-this) rule.
+It adds support for TypeScript's `this` parameters.
+
+## How to use
+
+```cjson
+{
+  // note you must disable the base rule as it can report incorrect errors
+  "no-invalid-this": "off",
+  "@typescript-eslint/no-invalid-this": ["error"]
+}
+```
+
+## Options
+
+See [`eslint/no-invalid-this` options](https://eslint.org/docs/rules/no-invalid-this#options).
+
+## When Not To Use It
+
+When you are indifferent as to how your variables are initialized.
+
+<sup>Taken with ❤️ [from ESLint core](https://github.com/eslint/eslint/blob/master/docs/rules/no-invalid-this.md)</sup>

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

@@ -52,6 +52,8 @@
     "@typescript-eslint/no-for-in-array": "error",
     "@typescript-eslint/no-implied-eval": "error",
     "@typescript-eslint/no-inferrable-types": "error",
+    "no-invalid-this": "off",
+    "@typescript-eslint/no-invalid-this": "error",
     "@typescript-eslint/no-invalid-void-type": "error",
     "no-magic-numbers": "off",
     "@typescript-eslint/no-magic-numbers": "error",

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

@@ -41,6 +41,7 @@ import noFloatingPromises from './no-floating-promises';
 import noForInArray from './no-for-in-array';
 import noImpliedEval from './no-implied-eval';
 import noInferrableTypes from './no-inferrable-types';
+import noInvalidThis from './no-invalid-this';
 import noInvalidVoidType from './no-invalid-void-type';
 import noMagicNumbers from './no-magic-numbers';
 import noMisusedNew from './no-misused-new';
@@ -145,6 +146,7 @@ export default {
   'no-for-in-array': noForInArray,
   'no-implied-eval': noImpliedEval,
   'no-inferrable-types': noInferrableTypes,
+  'no-invalid-this': noInvalidThis,
   'no-invalid-void-type': noInvalidVoidType,
   'no-magic-numbers': noMagicNumbers,
   'no-misused-new': noMisusedNew,

packages/eslint-plugin/src/rules/no-invalid-this.ts

@@ -0,0 +1,78 @@
+import {
+  TSESTree,
+  AST_NODE_TYPES,
+} from '@typescript-eslint/experimental-utils';
+import baseRule from 'eslint/lib/rules/no-invalid-this';
+import {
+  InferOptionsTypeFromRule,
+  createRule,
+  InferMessageIdsTypeFromRule,
+} from '../util';
+
+export type Options = InferOptionsTypeFromRule<typeof baseRule>;
+export type MessageIds = InferMessageIdsTypeFromRule<typeof baseRule>;
+
+export default createRule<Options, MessageIds>({
+  name: 'no-invalid-this',
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description:
+        'disallow `this` keywords outside of classes or class-like objects',
+      category: 'Best Practices',
+      recommended: false,
+      extendsBaseRule: true,
+    },
+    messages: baseRule.meta.messages,
+    schema: baseRule.meta.schema,
+  },
+  defaultOptions: [{ capIsConstructor: true }],
+  create(context) {
+    const rules = baseRule.create(context);
+    const argList: boolean[] = [];
+
+    return {
+      ...rules,
+      FunctionDeclaration(node: TSESTree.FunctionDeclaration): void {
+        argList.push(
+          node.params.some(
+            param =>
+              param.type === AST_NODE_TYPES.Identifier && param.name === 'this',
+          ),
+        );
+        // baseRule's work
+        rules.FunctionDeclaration(node);
+      },
+      'FunctionDeclaration:exit'(node: TSESTree.FunctionDeclaration): void {
+        argList.pop();
+        // baseRule's work
+        rules['FunctionDeclaration:exit'](node);
+      },
+      FunctionExpression(node: TSESTree.FunctionExpression): void {
+        argList.push(
+          node.params.some(
+            param =>
+              param.type === AST_NODE_TYPES.Identifier && param.name === 'this',
+          ),
+        );
+        // baseRule's work
+        rules.FunctionExpression(node);
+      },
+      'FunctionExpression:exit'(node: TSESTree.FunctionExpression): void {
+        argList.pop();
+        // baseRule's work
+        rules['FunctionExpression:exit'](node);
+      },
+      ThisExpression(node: TSESTree.ThisExpression): void {
+        const lastFnArg = argList[argList.length - 1];
+
+        if (lastFnArg) {
+          return;
+        }
+
+        // baseRule's work
+        rules.ThisExpression(node);
+      },
+    };
+  },
+});