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Add no-unreadable-iife rule (#1765)
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‎configs/recommended.js

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@@ -52,6 +52,7 @@ module.exports = {
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'unicorn/no-thenable': 'error',
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'unicorn/no-this-assignment': 'error',
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'unicorn/no-unreadable-array-destructuring': 'error',
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'unicorn/no-unreadable-iife': 'error',
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'unicorn/no-unsafe-regex': 'off',
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'unicorn/no-unused-properties': 'off',
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'unicorn/no-useless-fallback-in-spread': 'error',

‎docs/rules/no-unreadable-iife.md

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# Disallow unreadable IIFEs
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<!-- Do not manually modify RULE_NOTICE part. Run: `npm run generate-rule-notices` -->
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<!-- RULE_NOTICE -->
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✅ *This rule is part of the [recommended](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config) config.*
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<!-- /RULE_NOTICE -->
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[IIFE](https://en.wikipedia.org/wiki/Immediately_invoked_function_expression) with parenthesized arrow function body is considered unreadable.
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## Fail
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```js
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const foo = (bar => (bar ? bar.baz : baz))(getBar());
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```
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```js
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const foo = ((bar, baz) => ({bar, baz}))(bar, baz);
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```
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## Pass
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```js
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const bar = getBar();
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const foo = bar ? bar.baz : baz;
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```
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```js
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const getBaz = bar => (bar ? bar.baz : baz);
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const foo = getBaz(getBar());
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```
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```js
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const foo = (bar => {
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return bar ? bar.baz : baz;
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})(getBar());
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```

‎readme.md

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@@ -93,6 +93,7 @@ Each rule has emojis denoting:
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| [no-thenable](docs/rules/no-thenable.md) | Disallow `then` property. | ✅ | | |
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| [no-this-assignment](docs/rules/no-this-assignment.md) | Disallow assigning `this` to a variable. | ✅ | | |
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| [no-unreadable-array-destructuring](docs/rules/no-unreadable-array-destructuring.md) | Disallow unreadable array destructuring. | ✅ | 🔧 | |
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| [no-unreadable-iife](docs/rules/no-unreadable-iife.md) | Disallow unreadable IIFEs. | ✅ | | |
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| [no-unsafe-regex](docs/rules/no-unsafe-regex.md) | Disallow unsafe regular expressions. | | | |
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| [no-unused-properties](docs/rules/no-unused-properties.md) | Disallow unused object properties. | | | |
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| [no-useless-fallback-in-spread](docs/rules/no-useless-fallback-in-spread.md) | Disallow useless fallback when spreading in object literals. | ✅ | 🔧 | |

‎rules/no-unreadable-iife.js

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'use strict';
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const {
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isParenthesized,
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getParenthesizedRange,
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} = require('./utils/parentheses.js');
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const toLocation = require('./utils/to-location.js');
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const MESSAGE_ID_ERROR = 'no-unreadable-iife';
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const messages = {
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[MESSAGE_ID_ERROR]: 'IIFE with parenthesized arrow function body is considered unreadable.',
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};
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const selector = [
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'CallExpression',
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' > ',
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'ArrowFunctionExpression.callee',
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' > ',
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':not(BlockStatement).body',
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].join('');
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/** @param {import('eslint').Rule.RuleContext} context */
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const create = context => ({
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[selector](node) {
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const sourceCode = context.getSourceCode();
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if (!isParenthesized(node, sourceCode)) {
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return;
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}
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return {
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node,
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loc: toLocation(getParenthesizedRange(node, sourceCode), sourceCode),
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messageId: MESSAGE_ID_ERROR,
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};
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},
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});
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/** @type {import('eslint').Rule.RuleModule} */
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module.exports = {
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create,
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meta: {
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type: 'suggestion',
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docs: {
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description: 'Disallow unreadable IIFEs.',
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},
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hasSuggestions: false,
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messages,
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},
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};

‎test/no-unreadable-iife.mjs

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import outdent from 'outdent';
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import {getTester} from './utils/test.mjs';
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const {test} = getTester(import.meta);
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test.snapshot({
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valid: [
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'const foo = (bar => bar)();',
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outdent`
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const foo = (() => {
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return a ? b : c
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})();
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`,
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],
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invalid: [
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'const foo = (() => (a ? b : c))();',
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outdent`
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const foo = (() => (
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a ? b : c
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))();
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`,
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outdent`
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const foo = (
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() => (
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a ? b : c
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)
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)();
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`,
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outdent`
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const foo = (() => (
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a, b
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))();
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`,
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outdent`
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const foo = (() => ({
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a: b,
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}))();
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`,
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'const foo = (bar => (bar))();',
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outdent`
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(async () => ({
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bar,
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}))();
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`,
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outdent`
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const foo = (async (bar) => ({
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bar: await baz(),
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}))();
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`,
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'(async () => (( {bar} )))();',
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],
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});

‎test/snapshots/no-unreadable-iife.mjs.md

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# Snapshot report for `test/no-unreadable-iife.mjs`
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The actual snapshot is saved in `no-unreadable-iife.mjs.snap`.
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Generated by [AVA](https://avajs.dev).
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## Invalid #1
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1 | const foo = (() => (a ? b : c))();
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> Error 1/1
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`␊
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> 1 | const foo = (() => (a ? b : c))();␊
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| ^^^^^^^^^^^ IIFE with parenthesized arrow function body is considered unreadable.␊
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`
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## Invalid #2
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1 | const foo = (() => (
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2 | a ? b : c
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3 | ))();
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> Error 1/1
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`␊
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> 1 | const foo = (() => (␊
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| ^␊
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> 2 | a ? b : c␊
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| ^^^^^^^^^^␊
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> 3 | ))();␊
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| ^^ IIFE with parenthesized arrow function body is considered unreadable.␊
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`
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## Invalid #3
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1 | const foo = (
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2 | () => (
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3 | a ? b : c
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4 | )
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5 | )();
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> Error 1/1
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`␊
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1 | const foo = (␊
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> 2 | () => (␊
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| ^␊
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> 3 | a ? b : c␊
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| ^^^^^^^^^^^␊
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> 4 | )␊
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| ^^^ IIFE with parenthesized arrow function body is considered unreadable.␊
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5 | )();␊
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`
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## Invalid #4
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1 | const foo = (() => (
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2 | a, b
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3 | ))();
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> Error 1/1
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`␊
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> 1 | const foo = (() => (␊
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| ^␊
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> 2 | a, b␊
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| ^^^^^␊
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> 3 | ))();␊
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| ^^ IIFE with parenthesized arrow function body is considered unreadable.␊
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`
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## Invalid #5
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1 | const foo = (() => ({
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2 | a: b,
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3 | }))();
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> Error 1/1
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`␊
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> 1 | const foo = (() => ({␊
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| ^^␊
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> 2 | a: b,␊
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| ^^^^^^␊
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> 3 | }))();␊
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| ^^^ IIFE with parenthesized arrow function body is considered unreadable.␊
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`
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## Invalid #6
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1 | const foo = (bar => (bar))();
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> Error 1/1
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`␊
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> 1 | const foo = (bar => (bar))();␊
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| ^^^^^ IIFE with parenthesized arrow function body is considered unreadable.␊
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`
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## Invalid #7
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1 | (async () => ({
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2 | bar,
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3 | }))();
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> Error 1/1
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`␊
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> 1 | (async () => ({␊
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| ^^␊
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> 2 | bar,␊
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| ^^^^^␊
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> 3 | }))();␊
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| ^^^ IIFE with parenthesized arrow function body is considered unreadable.␊
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`
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## Invalid #8
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1 | const foo = (async (bar) => ({
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2 | bar: await baz(),
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3 | }))();
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> Error 1/1
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`␊
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> 1 | const foo = (async (bar) => ({␊
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| ^^␊
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> 2 | bar: await baz(),␊
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| ^^^^^^^^^^^^^^^^^^␊
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> 3 | }))();␊
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| ^^^ IIFE with parenthesized arrow function body is considered unreadable.␊
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`
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## Invalid #9
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1 | (async () => (( {bar} )))();
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> Error 1/1
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`␊
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> 1 | (async () => (( {bar} )))();␊
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| ^^^^^^^^^^^ IIFE with parenthesized arrow function body is considered unreadable.␊
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`

‎test/snapshots/no-unreadable-iife.mjs.snap

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