fix: avoid false positive in no-unassigned-vars for declare module (#19746)

azat-io · web-flow · commit 72d16e3066aa · 2025-05-25T12:26:38.000+02:00
* fix: avoid false positive in `no-unassigned-vars` for declare module

* docs: add declare module example in `no-unassigned-vars` rule

* perf: use flag instead of `getAncestors` in `no-unassigned-vars rule`

* test: add flag reset test for `no-unassigned-vars`
diff --git a/docs/src/rules/no-unassigned-vars.md b/docs/src/rules/no-unassigned-vars.md
@@ -129,6 +129,11 @@ In TypeScript:
 
 declare let value: number | undefined;
 console.log(value);
+
+declare module "my-module" {
+  let value: string;
+  export = value;
+}
 ```
 
 :::
diff --git a/lib/rules/no-unassigned-vars.js b/lib/rules/no-unassigned-vars.js
@@ -31,17 +31,25 @@ module.exports = {
 
 	create(context) {
 		const sourceCode = context.sourceCode;
+		let insideDeclareModule = false;
 
 		return {
+			"TSModuleDeclaration[declare=true]"() {
+				insideDeclareModule = true;
+			},
+			"TSModuleDeclaration[declare=true]:exit"() {
+				insideDeclareModule = false;
+			},
 			VariableDeclarator(node) {
 				/** @type {import('estree').VariableDeclaration} */
 				const declaration = node.parent;
-				const shouldCheck =
-					!node.init &&
-					node.id.type === "Identifier" &&
-					declaration.kind !== "const" &&
-					!declaration.declare;
-				if (!shouldCheck) {
+				const shouldSkip =
+					node.init ||
+					node.id.type !== "Identifier" ||
+					declaration.kind === "const" ||
+					declaration.declare ||
+					insideDeclareModule;
+				if (shouldSkip) {
 					return;
 				}
 				const [variable] = sourceCode.getDeclaredVariables(node);
diff --git a/tests/lib/rules/no-unassigned-vars.js b/tests/lib/rules/no-unassigned-vars.js
@@ -140,6 +140,13 @@ ruleTesterTypeScript.run("no-unassigned-vars", rule, {
 				}
 			}
 		`,
+		unIndent`
+			declare module 'module' {
+				import type { T } from 'module';
+				let x: T;
+				export = x;
+			}
+		`,
 	],
 	invalid: [
 		{
@@ -175,5 +182,22 @@ ruleTesterTypeScript.run("no-unassigned-vars", rule, {
 				},
 			],
 		},
+		{
+			code: unIndent`
+				declare module 'module' {
+					let x: string;
+				}
+				let y: string;
+				console.log(y);
+			`,
+			errors: [
+				{
+					messageId: "unassigned",
+					line: 4,
+					column: 9,
+					data: { name: "y" },
+				},
+			],
+		},
 	],
 });
