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feat: ignore IIFE's for no-loop-func rule #17426

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feat: ignore IIFE's for no-loop-func rule #17426

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18 changes: 18 additions & 0 deletions lib/rules/no-loop-func.js
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,8 @@

"use strict";

const astUtils = require("./utils/ast-utils");

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
Expand Down Expand Up @@ -144,6 +146,18 @@ function isSafe(loopNode, reference) {
return Boolean(variable) && variable.references.every(isSafeReference);
}

/**
* Determines if a given expression node is an IIFE
* @param {ASTNode} node The node to check
* @returns {boolean} `true` if the given node is an IIFE
*/
function isIIFE(node) {
const maybeCallNode = astUtils.skipChainExpression(node);

return maybeCallNode.type === "CallExpression" && (maybeCallNode.callee.type === "FunctionExpression" ||
maybeCallNode.callee.type === "ArrowFunctionExpression");
}

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
Expand Down Expand Up @@ -185,6 +199,10 @@ module.exports = {
return;
}

if (!node.async && !node.generator && isIIFE(node.parent)) {
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This would be a false negative:

/* eslint no-loop-func: "error" */

var arr = [];

for (var i = 0; i < 5; i++) {
    arr.push((f => f)(() => i)); // false negative, this is not a call of `() => i`
}

console.log(arr.map(f => f())); // [ 5, 5, 5, 5, 5 ]

Parent of () => i is a function call, but not a call of that function (() => i is an argument, not callee).

return;
}

const references = sourceCode.getScope(node).through;
const unsafeRefs = references.filter(r => r.resolved && !isSafe(loopNode, r)).map(r => r.identifier.name);

Expand Down
32 changes: 22 additions & 10 deletions tests/lib/rules/no-loop-func.js
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Original file line number Diff line number Diff line change
Expand Up @@ -112,6 +112,19 @@ ruleTester.run("no-loop-func", rule, {
].join("\n"),
parserOptions: { ecmaVersion: 6 }
},
{
code: "for (var i=0; (function() { i; })(), i<l; i++) { }",
errors: [{ messageId: "unsafeRefs", data: { varNames: "'i'" }, type: "FunctionExpression" }]
},

{
code: "for (let i = 0; i < 10; ++i) { (()=>{ i;})() }",
parserOptions: { ecmaVersion: 6 }
},
{
code: "for (let i = 0; i < 10; ++i) { (function a(){i;})() }",
parserOptions: { ecmaVersion: 6 }
},

/*
* These loops _look_ like they might be unsafe, but because i is undeclared, they're fine
Expand Down Expand Up @@ -149,13 +162,15 @@ ruleTester.run("no-loop-func", rule, {
code: "for (let i in {}) { i = 7; (function() { undeclared; }) }",
parserOptions: { ecmaVersion: 6 }
},

/* The references to loop variable are inside an IIFE so they are safe */
{
code: "for (const i of {}) { (function() { undeclared; }) }",
parserOptions: { ecmaVersion: 6 }
},
{
code: "for (let i = 0; i < 10; ++i) { for (let x in xs.filter(x => x != undeclared)) { } }",
parserOptions: { ecmaVersion: 6 }
code: "for (var i=0; i<l; (function() { i; })(), i++) { }",
errors: [{ messageId: "unsafeRefs", data: { varNames: "'i'" }, type: "FunctionExpression" }]
}

],
Expand Down Expand Up @@ -190,14 +205,6 @@ ruleTester.run("no-loop-func", rule, {
code: "for (var i=0; i < l; i++) { function a() { i; }; a(); }",
errors: [{ messageId: "unsafeRefs", data: { varNames: "'i'" }, type: "FunctionDeclaration" }]
},
{
code: "for (var i=0; (function() { i; })(), i<l; i++) { }",
errors: [{ messageId: "unsafeRefs", data: { varNames: "'i'" }, type: "FunctionExpression" }]
},
{
code: "for (var i=0; i<l; (function() { i; })(), i++) { }",
errors: [{ messageId: "unsafeRefs", data: { varNames: "'i'" }, type: "FunctionExpression" }]
},

// Warns functions which are using modified variables.
{
Expand Down Expand Up @@ -269,6 +276,11 @@ ruleTester.run("no-loop-func", rule, {
code: "let a; function foo() { a = 10; for (let x of xs) { (function() { a; }); } } foo();",
parserOptions: { ecmaVersion: 6 },
errors: [{ messageId: "unsafeRefs", data: { varNames: "'a'" }, type: "FunctionExpression" }]
},
{
code: "let a; for (var i=0; i<l; i++) { (function* (){i;})() }",
parserOptions: { ecmaVersion: 6 },
errors: [{ messageId: "unsafeRefs", data: { varNames: "'i'" }, type: "FunctionExpression" }]
}
]
});