typescript-eslint · bradzacher · Apr 11, 2019 · Feb 23, 2019 · Feb 25, 2019 · Feb 25, 2019
diff --git a/packages/eslint-plugin/docs/rules/no-extra-parens.md b/packages/eslint-plugin/docs/rules/no-extra-parens.md
@@ -0,0 +1,22 @@
+# disallow unnecessary parentheses (no-extra-parens)
+
+This rule restricts the use of parentheses to only where they are necessary.
+
+## Rule Details
+
+This rule extends the base [eslint/no-extra-parens](https://eslint.org/docs/rules/no-extra-parens) rule.
+It supports all options and features of the base rule plus TS type assertions.
+
+## How to use
+
+```cjson
+{
+    // note you must disable the base rule as it can report incorrect errors
+    "no-extra-parens": "off",
+    "@typescript-eslint/no-extra-parens": ["error"]
+}
+```
+
+## Options
+
+See [eslint/no-extra-parens options](https://eslint.org/docs/rules/no-extra-parens#options).
diff --git a/packages/eslint-plugin/src/rules/no-extra-parens.ts b/packages/eslint-plugin/src/rules/no-extra-parens.ts
@@ -0,0 +1,33 @@
+import { TSESTree, AST_NODE_TYPES } from '@typescript-eslint/typescript-estree';
+import baseRule from 'eslint/lib/rules/no-extra-parens';
+import * as util from '../util';
+
+type Options = util.InferOptionsTypeFromRule<typeof baseRule>;
+type MessageIds = util.InferMessageIdsTypeFromRule<typeof baseRule>;
+
+export default util.createRule<Options, MessageIds>({
+  name: 'no-extra-parens',
+  meta: {
+    type: 'layout',
+    docs: {
+      description: 'disallow unnecessary parentheses',
+      category: 'Possible Errors',
+      recommended: false,
+    },
+    fixable: 'code',
+    schema: baseRule.meta.schema,
+    messages: baseRule.meta.messages,
+  },
+  defaultOptions: ['all'],
+  create(context) {
+    const rules = baseRule.create(context);
+
+    return Object.assign({}, rules, {
+      MemberExpression(node: TSESTree.MemberExpression) {
+        if (node.object.type !== AST_NODE_TYPES.TSAsExpression) {
+          return rules.MemberExpression(node);
+        }
+      },
+    });
+  },
+});
diff --git a/packages/eslint-plugin/tests/rules/no-extra-parens.test.ts b/packages/eslint-plugin/tests/rules/no-extra-parens.test.ts
@@ -0,0 +1,266 @@
+import rule from '../../src/rules/no-extra-parens';
+import { RuleTester } from '../RuleTester';
+
+const ruleTester = new RuleTester({
+  parserOptions: {
+    ecmaFeatures: {
+      jsx: true,
+    },
+  },
+  parser: '@typescript-eslint/parser',
+});
+
+ruleTester.run('no-extra-parens', rule, {
+  valid: [
+    {
+      code: `
+        (0).toString();
+        (function(){}) ? a() : b();        
+        (/^a$/).test(x);       
+        for (a of (b, c));        
+        for (a of b);     
+        for (a in b, c);  
+        for (a in b);
+      `,
+    },
+    {
+      code: `t.true((me.get as SinonStub).calledWithExactly('/foo', other));`,
+    },
+    {
+      code: `while ((foo = bar())) {}`,
+      options: ['all', { conditionalAssign: false }],
+    },
+    {
+      code: `if ((foo = bar())) {}`,
+      options: ['all', { conditionalAssign: false }],
+    },
+    {
+      code: `do; while ((foo = bar()))`,
+      options: ['all', { conditionalAssign: false }],
+    },
+    {
+      code: `for (;(a = b););`,
+      options: ['all', { conditionalAssign: false }],
+    },
+    {
+      code: `
+        function a(b) {
+          return (b = 1);
+        }
+      `,
+      options: ['all', { returnAssign: false }],
+    },
+    {
+      code: `
+        function a(b) {
+          return b ? (c = d) : (c = e);
+        }
+      `,
+      options: ['all', { returnAssign: false }],
+    },
+    {
+      code: `b => (b = 1);`,
+      options: ['all', { returnAssign: false }],
+    },
+    {
+      code: `b => b ? (c = d) : (c = e);`,
+      options: ['all', { returnAssign: false }],
+    },
+    {
+      code: `x = a || (b && c);`,
+      options: ['all', { nestedBinaryExpressions: false }],
+    },
+    {
+      code: `x = a + (b * c);`,
+      options: ['all', { nestedBinaryExpressions: false }],
+    },
+    {
+      code: `x = (a * b) / c;`,
+      options: ['all', { nestedBinaryExpressions: false }],
+    },
+    {
+      code: `
+        const Component = (<div />)
+        const Component = (
+            <div
+                prop={true}
+            />
+        )
+      `,
+      options: ['all', { ignoreJSX: 'all' }],
+    },
+    {
+      code: `
+        const Component = (
+            <div>
+                <p />
+            </div>
+        )
+        const Component = (
+            <div
+                prop={true}
+            />
+        )
+      `,
+      options: ['all', { ignoreJSX: 'multi-line' }],
+    },
+    {
+      code: `
+        const Component = (<div />)
+        const Component = (<div><p /></div>)
+      `,
+      options: ['all', { ignoreJSX: 'single-line' }],
+    },
+    {
+      code: `
+        const b = a => 1 ? 2 : 3;
+        const d = c => (1 ? 2 : 3);
+      `,
+      options: ['all', { enforceForArrowConditionals: false }],
+    },
+    {
+      code: `
+        (0).toString();
+        (Object.prototype.toString.call());
+        ({}.toString.call());
+        (function(){} ? a() : b());
+        (/^a$/).test(x);
+        a = (b * c);
+        (a * b) + c;
+        typeof (a);
+      `,
+      options: ['functions'],
+    },
+  ],
+
+  invalid: [
+    {
+      code: `a = (b * c);`,
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 1,
+          column: 5,
+        },
+      ],
+    },
+    {
+      code: `(a * b) + c;`,
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 1,
+          column: 1,
+        },
+      ],
+    },
+    {
+      code: `for (a in (b, c));`,
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 1,
+          column: 11,
+        },
+      ],
+    },
+    {
+      code: `for (a in (b));`,
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 1,
+          column: 11,
+        },
+      ],
+    },
+    {
+      code: `for (a of (b));`,
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 1,
+          column: 11,
+        },
+      ],
+    },
+    {
+      code: `typeof (a);`,
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 1,
+          column: 8,
+        },
+      ],
+    },
+    {
+      code: `
+        const Component = (<div />)
+        const Component = (<div><p /></div>)
+      `,
+      options: ['all', { ignoreJSX: 'multi-line' }],
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 2,
+          column: 27,
+        },
+        {
+          messageId: 'unexpected',
+          line: 3,
+          column: 27,
+        },
+      ],
+    },
+    {
+      code: `
+        const Component = (
+            <div>
+                <p />
+            </div>
+        )
+        const Component = (
+            <div
+                prop={true}
+            />
+        )
+      `,
+      options: ['all', { ignoreJSX: 'single-line' }],
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 2,
+          column: 27,
+        },
+        {
+          messageId: 'unexpected',
+          line: 7,
+          column: 27,
+        },
+      ],
+    },
+    {
+      code: `((function foo() {}))();`,
+      options: ['functions'],
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 1,
+          column: 2,
+        },
+      ],
+    },
+    {
+      code: `var y = (function () {return 1;});`,
+      options: ['functions'],
+      errors: [
+        {
+          messageId: 'unexpected',
+          line: 1,
+          column: 9,
+        },
+      ],
+    },
+  ],
+});
diff --git a/packages/eslint-plugin/typings/eslint-rules.d.ts b/packages/eslint-plugin/typings/eslint-rules.d.ts
@@ -330,3 +330,26 @@ declare module 'eslint/lib/rules/no-useless-constructor' {
   >;
   export = rule;
 }
+
+declare module 'eslint/lib/rules/no-extra-parens' {
+  import { TSESTree } from '@typescript-eslint/typescript-estree';
+  import RuleModule from 'ts-eslint';
+
+  const rule: RuleModule<
+    'unexpected',
+    (
+      | 'all'
+      | 'functions'
+      | {
+          conditionalAssign?: boolean;
+          returnAssign?: boolean;
+          nestedBinaryExpressions?: boolean;
+          ignoreJSX?: 'none' | 'all' | 'multi-line' | 'single-line';
+          enforceForArrowConditionals?: boolean;
+        })[],
+    {
+      MemberExpression(node: TSESTree.MemberExpression): void;
+    }
+  >;
+  export = rule;
+}
diff --git a/packages/eslint-plugin/typings/ts-eslint.d.ts b/packages/eslint-plugin/typings/ts-eslint.d.ts
@@ -209,7 +209,11 @@ declare module 'ts-eslint' {
     /**
      * The general category the rule falls within
      */
-    category: 'Best Practices' | 'Stylistic Issues' | 'Variables';
+    category:
+      | 'Best Practices'
+      | 'Stylistic Issues'
+      | 'Variables'
+      | 'Possible Errors';
     /**
      * Concise description of the rule
      */

diff --git a/packages/typescript-estree/src/ts-estree/ts-estree.ts b/packages/typescript-estree/src/ts-estree/ts-estree.ts
@@ -323,7 +323,8 @@ export type LeftHandSideExpression =
   | MemberExpression
   | PrimaryExpression
   | TaggedTemplateExpression
-  | TSNonNullExpression;
+  | TSNonNullExpression
+  | TSAsExpression;
 export type LiteralExpression = BigIntLiteral | Literal | TemplateLiteral;
 export type Modifier =
   | TSAbstractKeyword