feat: support explicit resource management in init-declarations (#19893)

mdjermanovic · web-flow · commit 58482165eaf5 · 2025-07-04T06:15:56.000+02:00
diff --git a/docs/src/rules/init-declarations.md b/docs/src/rules/init-declarations.md
@@ -36,7 +36,7 @@ This rule aims to bring consistency to variable initializations and declarations
 
 The rule takes two options:
 
-1. A string which must be either `"always"` (the default), to enforce initialization at declaration, or `"never"` to disallow initialization during declaration. This rule applies to `var`, `let`, and `const` variables, however `"never"` is ignored for `const` variables, as unassigned `const`s generate a parse error.
+1. A string which must be either `"always"` (the default), to enforce initialization at declaration, or `"never"` to disallow initialization during declaration. This rule applies to `var`, `let`, `const`, `using`, and `await using` variables, however `"never"` is ignored for `const`, `using`, and `await using` variables, as not initializing these variables would generate a parse error.
 2. An object that further controls the behavior of this rule. Currently, the only available parameter is `ignoreForLoopInit`, which indicates if initialization at declaration is allowed in `for` loops when `"never"` is set, since it is a very typical use case.
 
 You can configure the rule as follows:
@@ -93,6 +93,11 @@ function foo() {
     var bar = 1;
     let baz = 2;
     const qux = 3;
+	using quux = getSomething();
+}
+
+async function foobar() {
+	await using quux = getSomething();
 }
 ```
 
@@ -128,12 +133,17 @@ function foo() {
     var bar;
     let baz;
     const buzz = 1;
+	using quux = getSomething();
+}
+
+async function foobar() {
+	await using quux = getSomething();
 }
 ```
 
 :::
 
-The `"never"` option ignores `const` variable initializations.
+The `"never"` option ignores `const`, `using`, and `await using` variable initializations.
 
 ### ignoreForLoopInit
 
diff --git a/lib/rules/init-declarations.js b/lib/rules/init-declarations.js
@@ -9,6 +9,8 @@
 // Helpers
 //------------------------------------------------------------------------------
 
+const CONSTANT_BINDINGS = new Set(["const", "using", "await using"]);
+
 /**
  * Checks whether or not a given node is a for loop.
  * @param {ASTNode} block A node to check.
@@ -147,7 +149,7 @@ module.exports = {
 						messageId = "initialized";
 					} else if (
 						mode === MODE_NEVER &&
-						kind !== "const" &&
+						!CONSTANT_BINDINGS.has(kind) &&
 						initialized &&
 						!isIgnoredForLoop
 					) {
diff --git a/tests/lib/rules/init-declarations.js b/tests/lib/rules/init-declarations.js
@@ -39,6 +39,16 @@ ruleTester.run("init-declarations", rule, {
 			options: ["always"],
 			languageOptions: { ecmaVersion: 6 },
 		},
+		{
+			code: "using a = foo();",
+			options: ["always"],
+			languageOptions: { ecmaVersion: 2026 },
+		},
+		{
+			code: "await using a = foo();",
+			options: ["always"],
+			languageOptions: { ecmaVersion: 2026 },
+		},
 		{
 			code: "function foo() { let a = 1, b = false; if (a) { let c = 3, d = null; } }",
 			options: ["always"],
@@ -79,6 +89,16 @@ ruleTester.run("init-declarations", rule, {
 			options: ["never"],
 			languageOptions: { ecmaVersion: 6 },
 		},
+		{
+			code: "using a = foo();",
+			options: ["never"],
+			languageOptions: { ecmaVersion: 2026 },
+		},
+		{
+			code: "await using a = foo();",
+			options: ["never"],
+			languageOptions: { ecmaVersion: 2026 },
+		},
 		{
 			code: "function foo() { let a, b; if (a) { let c, d; } }",
 			options: ["never"],
