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feat: support explicit resource management in no-const-assign (#19892)
* feat: support explicit resource management in `no-const-assign` * update When Not To Use It section * fix typo
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‎docs/src/rules/no-const-assign.md‎

Lines changed: 39 additions & 6 deletions
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@@ -6,14 +6,11 @@ handled_by_typescript: true
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9-
We cannot modify variables that are declared using `const` keyword.
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It will raise a runtime error.
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Under non ES2015 environment, it might be ignored merely.
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Constant bindings cannot be modified. An attempt to modify a constant binding will raise a runtime error.
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## Rule Details
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This rule is aimed to flag modifying variables that are declared using `const` keyword.
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This rule is aimed to flag modifying variables that are declared using `const`, `using`, or `await using` keywords.
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Examples of **incorrect** code for this rule:
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@@ -50,6 +47,24 @@ const a = 0;
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:::
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::: incorrect
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```js
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/*eslint no-const-assign: "error"*/
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if (foo) {
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using a = getSomething();
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a = somethingElse;
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}
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if (bar) {
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await using a = getSomething();
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a = somethingElse;
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}
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```
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:::
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Examples of **correct** code for this rule:
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::: correct
@@ -68,6 +83,24 @@ console.log(a);
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```js
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/*eslint no-const-assign: "error"*/
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if (foo) {
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using a = getSomething();
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a.execute();
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}
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if (bar) {
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await using a = getSomething();
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a.execute();
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}
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```
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:::
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::: correct
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```js
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/*eslint no-const-assign: "error"*/
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for (const a in [1, 2, 3]) { // `a` is re-defined (not modified) on each loop step.
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console.log(a);
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}
@@ -89,4 +122,4 @@ for (const a of [1, 2, 3]) { // `a` is re-defined (not modified) on each loop st
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## When Not To Use It
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If you don't want to be notified about modifying variables that are declared using `const` keyword, you can safely disable this rule.
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If you don't want to be notified about modifying variables that are declared using `const`, `using`, and `await using` keywords, you can safely disable this rule.

‎lib/rules/no-const-assign.js‎

Lines changed: 13 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -5,8 +5,18 @@
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const astUtils = require("./utils/ast-utils");
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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const CONSTANT_BINDINGS = new Set(["const", "using", "await using"]);
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
@@ -17,7 +27,8 @@ module.exports = {
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type: "problem",
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docs: {
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description: "Disallow reassigning `const` variables",
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description:
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"Disallow reassigning `const`, `using`, and `await using` variables",
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recommended: true,
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url: "https://eslint.org/docs/latest/rules/no-const-assign",
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},
@@ -51,7 +62,7 @@ module.exports = {
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return {
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VariableDeclaration(node) {
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if (node.kind === "const") {
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if (CONSTANT_BINDINGS.has(node.kind)) {
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sourceCode
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.getDeclaredVariables(node)
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.forEach(checkVariable);

‎lib/types/rules.d.ts‎

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@@ -2126,7 +2126,7 @@ export interface ESLintRules extends Linter.RulesRecord {
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>;
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/**
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* Rule to disallow reassigning `const` variables.
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* Rule to disallow reassigning `const`, `using`, and `await using` variables.
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*
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* @remarks
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* Recommended by ESLint, the rule was enabled in `eslint:recommended`.

‎tests/lib/rules/no-const-assign.js‎

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Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@ const RuleTester = require("../../../lib/rule-tester/rule-tester");
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// Tests
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//------------------------------------------------------------------------------
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const ruleTester = new RuleTester({ languageOptions: { ecmaVersion: 6 } });
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const ruleTester = new RuleTester();
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ruleTester.run("no-const-assign", rule, {
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valid: [
@@ -26,6 +26,10 @@ ruleTester.run("no-const-assign", rule, {
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"for (const x in [1,2,3]) { foo(x); }",
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"for (const x of [1,2,3]) { foo(x); }",
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"const x = {key: 0}; x.key = 1;",
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"using x = foo();",
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"await using x = foo();",
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"using x = foo(); bar(x);",
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"await using x = foo(); bar(x);",
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// ignores non constant.
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"var x = 0; x = 1;",
@@ -115,5 +119,71 @@ ruleTester.run("no-const-assign", rule, {
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{ messageId: "const", data: { name: "x" }, type: "Identifier" },
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],
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},
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{
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code: "using x = foo(); x = 1;",
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errors: [
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{
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messageId: "const",
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data: { name: "x" },
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type: "Identifier",
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column: 18,
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},
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],
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},
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{
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code: "await using x = foo(); x = 1;",
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errors: [
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{
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messageId: "const",
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data: { name: "x" },
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type: "Identifier",
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column: 24,
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},
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],
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},
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{
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code: "using x = foo(); x ??= bar();",
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errors: [
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{
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messageId: "const",
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data: { name: "x" },
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type: "Identifier",
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column: 18,
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},
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],
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},
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{
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code: "await using x = foo(); x ||= bar();",
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errors: [
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{
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messageId: "const",
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data: { name: "x" },
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type: "Identifier",
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column: 24,
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},
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],
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},
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{
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code: "using x = foo(); [x, y] = bar();",
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errors: [
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{
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messageId: "const",
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data: { name: "x" },
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type: "Identifier",
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column: 19,
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},
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],
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},
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{
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code: "await using x = foo(); [x = baz, y] = bar();",
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errors: [
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{
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messageId: "const",
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data: { name: "x" },
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type: "Identifier",
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column: 25,
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},
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],
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},
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],
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});

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