tools: avoid let in for loops
This adds a new ESLint tool to check for let declarations within the for, forIn, forOf expressions. Fixes: https://github.com/nodejs/node/issues/9045 Ref: https://github.com/nodejs/node/pull/8873 PR-URL: https://github.com/nodejs/node/pull/9049 Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Myles Borins <myles.borins@gmail.com> Reviewed-By: Teddy Katz <teddy.katz@gmail.com> Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>
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@ -2,3 +2,4 @@ rules:
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# Custom rules in tools/eslint-rules
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require-buffer: 2
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buffer-constructor: 2
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no-let-in-for-declaration: 2
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46
tools/eslint-rules/no-let-in-for-declaration.js
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46
tools/eslint-rules/no-let-in-for-declaration.js
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@ -0,0 +1,46 @@
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/**
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* @fileoverview Prohibit the use of `let` as the loop variable
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* in the initialization of for, and the left-hand
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* iterator in forIn and forOf loops.
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*
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* @author Jessica Quynh Tran
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*/
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'use strict';
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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create(context) {
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const msg = 'Use of `let` as the loop variable in a for-loop is ' +
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'not recommended. Please use `var` instead.';
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/**
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* Report function to test if the for-loop is declared using `let`.
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*/
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function testForLoop(node) {
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if (node.init && node.init.kind === 'let') {
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context.report(node.init, msg);
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}
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}
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/**
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* Report function to test if the for-in or for-of loop
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* is declared using `let`.
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*/
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function testForInOfLoop(node) {
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if (node.left && node.left.kind === 'let') {
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context.report(node.left, msg);
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}
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}
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return {
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'ForStatement': testForLoop,
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'ForInStatement': testForInOfLoop,
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'ForOfStatement': testForInOfLoop
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};
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}
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};
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