feat(eslint-plugin): [no-explicit-any] Add an optional fixer (#609)

Author: aggmoulik

Diff for: packages/eslint-plugin/README.md

@@ -145,7 +145,7 @@ Then you should add `airbnb` (or `airbnb-base`) to your `extends` section of `.e
 | [`@typescript-eslint/no-array-constructor`](./docs/rules/no-array-constructor.md)                         | Disallow generic `Array` constructors                                                                                                               | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/no-empty-function`](./docs/rules/no-empty-function.md)                               | Disallow empty functions                                                                                                                            |                    |          |                   |
 | [`@typescript-eslint/no-empty-interface`](./docs/rules/no-empty-interface.md)                             | Disallow the declaration of empty interfaces                                                                                                        | :heavy_check_mark: |          |                   |
-| [`@typescript-eslint/no-explicit-any`](./docs/rules/no-explicit-any.md)                                   | Disallow usage of the `any` type                                                                                                                    | :heavy_check_mark: |          |                   |
+| [`@typescript-eslint/no-explicit-any`](./docs/rules/no-explicit-any.md)                                   | Disallow usage of the `any` type                                                                                                                    | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/no-extra-parens`](./docs/rules/no-extra-parens.md)                                   | Disallow unnecessary parentheses                                                                                                                    |                    | :wrench: |                   |
 | [`@typescript-eslint/no-extraneous-class`](./docs/rules/no-extraneous-class.md)                           | Forbids the use of classes as namespaces                                                                                                            |                    |          |                   |
 | [`@typescript-eslint/no-floating-promises`](./docs/rules/no-floating-promises.md)                         | Requires Promise-like values to be handled appropriately.                                                                                           |                    |          | :thought_balloon: |

Diff for: packages/eslint-plugin/docs/rules/no-explicit-any.md

@@ -87,6 +87,24 @@ function greet(param: Array<string>): string {}
 function greet(param: Array<string>): Array<string> {}
 ```
 
+## Options
+
+The rule accepts an options object with the following properties:
+
+```ts
+type Options = {
+  // if true, auto-fixing will be made available in which the "any" type is converted to an "unknown" type
+  fixToUnknown: boolean;
+  // specify if arrays from the rest operator are considered okay
+  ignoreRestArgs: boolean;
+};
+
+const defaults = {
+  fixToUnknown: false,
+  ignoreRestArgs: false,
+};
+```
+
 ### ignoreRestArgs
 
 A boolean to specify if arrays from the rest operator are considered okay. `false` by default.

Diff for: packages/eslint-plugin/src/rules/no-explicit-any.ts

@@ -3,8 +3,17 @@ import {
   AST_NODE_TYPES,
 } from '@typescript-eslint/experimental-utils';
 import * as util from '../util';
+import { TSESLint } from '@typescript-eslint/experimental-utils';
 
-export default util.createRule({
+export type Options = [
+  {
+    fixToUnknown?: boolean;
+    ignoreRestArgs?: boolean;
+  }
+];
+export type MessageIds = 'unexpectedAny';
+
+export default util.createRule<Options, MessageIds>({
   name: 'no-explicit-any',
   meta: {
     type: 'suggestion',
@@ -13,6 +22,7 @@ export default util.createRule({
       category: 'Best Practices',
       recommended: 'warn',
     },
+    fixable: 'code',
     messages: {
       unexpectedAny: 'Unexpected any. Specify a different type.',
     },
@@ -21,6 +31,9 @@ export default util.createRule({
         type: 'object',
         additionalProperties: false,
         properties: {
+          fixToUnknown: {
+            type: 'boolean',
+          },
           ignoreRestArgs: {
             type: 'boolean',
           },
@@ -30,10 +43,11 @@ export default util.createRule({
   },
   defaultOptions: [
     {
+      fixToUnknown: false,
       ignoreRestArgs: false,
     },
   ],
-  create(context, [{ ignoreRestArgs }]) {
+  create(context, [{ ignoreRestArgs, fixToUnknown }]) {
     /**
      * Checks if the node is an arrow function, function declaration or function expression
      * @param node the node to be validated.
@@ -155,9 +169,17 @@ export default util.createRule({
         if (ignoreRestArgs && isNodeDescendantOfRestElementInFunction(node)) {
           return;
         }
+
+        let fix: TSESLint.ReportFixFunction | null = null;
+
+        if (fixToUnknown) {
+          fix = fixer => fixer.replaceText(node, 'unknown');
+        }
+
         context.report({
           node,
           messageId: 'unexpectedAny',
+          fix,
         });
       },
     };

Diff for: packages/eslint-plugin/tests/rules/no-explicit-any.test.ts

@@ -1,5 +1,8 @@
-import rule from '../../src/rules/no-explicit-any';
+import rule, { MessageIds, Options } from '../../src/rules/no-explicit-any';
 import { RuleTester } from '../RuleTester';
+import { TSESLint } from '@typescript-eslint/experimental-utils';
+
+type InvalidTestCase = TSESLint.InvalidTestCase<MessageIds, Options>;
 
 const ruleTester = new RuleTester({
   parser: '@typescript-eslint/parser',
@@ -187,7 +190,7 @@ type obj = {
       options: [{ ignoreRestArgs: true }],
     },
   ],
-  invalid: [
+  invalid: ([
     {
       code: 'const number: any = 1',
       errors: [
@@ -784,5 +787,23 @@ type obj = {
         },
       ],
     },
-  ],
+  ] as InvalidTestCase[]).reduce<InvalidTestCase[]>((acc, testCase) => {
+    acc.push(testCase);
+    const options = testCase.options || [];
+    const code = `// fixToUnknown: true\n${testCase.code}`;
+    acc.push({
+      code,
+      output: code.replace(/any/g, 'unknown'),
+      options: [{ ...options[0], fixToUnknown: true }],
+      errors: testCase.errors.map(err => {
+        if (err.line === undefined) {
+          return err;
+        }
+
+        return { ...err, line: err.line + 1 };
+      }),
+    });
+
+    return acc;
+  }, []),
 });