fix: prevent unchecked indexed access

package.json

@@ -86,7 +86,7 @@
 		"semantic-release": "^25.0.2",
 		"semver": "^7.6.3",
 		"tsdown": "^0.17.3",
-		"typescript": "^5.7.2",
+		"typescript": "^5.9.3",
 		"typescript-eslint": "^8.15.0",
 		"vitest": "^3.2.4"
 	},

src/create-testing-library-rule/detect-testing-library-utils.ts

@@ -317,7 +317,7 @@ export function detectTestingLibraryUtils<
 
 		// Helpers for Testing Library detection.
 		const getTestingLibraryImportNode: GetTestingLibraryImportNodeFn = () => {
-			return importedTestingLibraryNodes[0];
+			return importedTestingLibraryNodes[0] ?? null;
 		};
 
 		const getAllTestingLibraryImportNodes: GetTestingLibraryImportNodesFn =

src/node-utils/accessors.ts

@@ -47,7 +47,7 @@ const isSimpleTemplateLiteral = <V extends string>(
 ): node is TemplateLiteral<V> =>
 	isTemplateLiteral(node) &&
 	node.quasis.length === 1 && // bail out if not simple
-	(value === undefined || node.quasis[0].value.raw === value);
+	(value === undefined || node.quasis[0]?.value.raw === value);
 
 export type StringNode<S extends string = string> =
 	| StringLiteral<S>

src/rules/no-container.ts

@@ -144,7 +144,7 @@ export default createTestingLibraryRule<Options, MessageIds>({
 					);
 
 					const nodeValue =
-						containerIndex !== -1 && node.id.properties[containerIndex].value;
+						containerIndex !== -1 && node.id.properties[containerIndex]?.value;
 
 					if (!nodeValue) {
 						return;

src/rules/no-global-regexp-flag-in-query.ts

@@ -124,7 +124,9 @@ export default createTestingLibraryRule<Options, MessageIds>({
 
 				const [firstArg, secondArg] = getArguments(identifierNode);
 
-				const firstArgumentHasError = reportLiteralWithRegex(firstArg);
+				const firstArgumentHasError = firstArg
+					? reportLiteralWithRegex(firstArg)
+					: false;
 				if (firstArgumentHasError) {
 					return;
 				}

src/rules/no-manual-cleanup.ts

@@ -69,9 +69,14 @@ export default createTestingLibraryRule<Options, MessageIds>({
 			if (isImportDeclaration(moduleNode)) {
 				// case: import utils from 'testing-library-module'
 				if (isImportDefaultSpecifier(moduleNode.specifiers[0])) {
-					const { references } = getDeclaredVariables(context, moduleNode)[0];
+					const declaredVariables = getDeclaredVariables(
+						context,
+						moduleNode
+					)[0];
 
-					reportImportReferences(references);
+					if (declaredVariables) {
+						reportImportReferences(declaredVariables.references);
+					}
 				}
 
 				// case: import { cleanup } from 'testing-library-module'

src/rules/no-promise-in-fire-event.ts

@@ -111,6 +111,9 @@ export default createTestingLibraryRule<Options, MessageIds>({
 
 				const domElementArgument = closestCallExpression.arguments[0];
 
+				if (!domElementArgument) {
+					return;
+				}
 				checkSuspiciousNode(domElementArgument);
 			},
 		};

src/rules/no-wait-for-multiple-assertions.ts

@@ -122,7 +122,7 @@ export default createTestingLibraryRule<Options, MessageIds>({
 							});
 							const lines = sourceCode.getText().split('\n');
 							const line = lines[callExpressionNode.loc.start.line - 1];
-							const indent = line.match(/^\s*/)?.[0] ?? '';
+							const indent = line?.match(/^\s*/)?.[0] ?? '';
 
 							const expressionStatementLines = lines.slice(
 								expressionStatement.loc.start.line - 1,

src/rules/no-wait-for-side-effects.ts

@@ -227,7 +227,7 @@ export default createTestingLibraryRule<Options, MessageIds>({
 
 						const lines = sourceCode.getText().split('\n');
 						const line = lines[targetNode.loc.start.line - 1];
-						const indent = line.match(/^\s*/)?.[0] ?? '';
+						const indent = line?.match(/^\s*/)?.[0] ?? '';
 						const sideEffectLines = lines.slice(
 							sideEffectNode.loc.start.line - 1,
 							sideEffectNode.loc.end.line

src/rules/prefer-find-by.ts

@@ -388,6 +388,11 @@ export default createTestingLibraryRule<Options, MessageIds>({
 					const queryMethod = fullQueryMethod.split('By')[1];
 					const queryVariant = getFindByQueryVariant(fullQueryMethod);
 
+					if (!queryMethod) {
+						// We shouldn't reach this point, but it's a safeguard for TS noUncheckedIndexedAccess
+						throw Error('Query method could not be determined.');
+					}
+
 					reportInvalidUsage(node, {
 						queryMethod,
 						queryVariant,
@@ -399,7 +404,7 @@ export default createTestingLibraryRule<Options, MessageIds>({
 								.slice(1, -1)
 								.trim();
 							const { line, column } = expressionStatement.loc.start;
-							const indent = sourceCode.getLines()[line - 1].slice(0, column);
+							const indent = sourceCode.getLines()[line - 1]?.slice(0, column);
 							const newText = bodyText
 								.split('\n')
 								.map((line) => line.trim())
@@ -498,6 +503,11 @@ export default createTestingLibraryRule<Options, MessageIds>({
 				const queryVariant = getFindByQueryVariant(fullQueryMethod);
 				const callArguments = getQueryArguments(argumentBody);
 
+				if (!queryMethod) {
+					// We shouldn't reach this point, but it's a safeguard for TS noUncheckedIndexedAccess
+					throw Error('Query method could not be determined.');
+				}
+
 				reportInvalidUsage(node, {
 					queryMethod,
 					queryVariant,

src/rules/prefer-query-by-disappearance.ts

@@ -178,6 +178,10 @@ export default createTestingLibraryRule<Options, MessageIds>({
 
 			const argumentNode = node.arguments[0];
 
+			if (!argumentNode) {
+				return;
+			}
+
 			checkNonCallbackViolation(argumentNode);
 			checkArrowFunctionViolation(argumentNode);
 			checkFunctionExpressionViolation(argumentNode);

src/rules/prefer-user-event.ts

@@ -56,9 +56,10 @@ export const MAPPING_TO_USER_EVENT: Record<string, UserEventMethodsType[]> = {
 };
 
 function buildErrorMessage(fireEventMethod: string) {
-	const userEventMethods = MAPPING_TO_USER_EVENT[fireEventMethod].map(
-		(methodName) => `userEvent.${methodName}`
-	);
+	const userEventMethods =
+		MAPPING_TO_USER_EVENT[fireEventMethod]?.map(
+			(methodName) => `userEvent.${methodName}`
+		) ?? [];
 
 	// TODO: when min node version is 13, we can reimplement this using `Intl.ListFormat`
 	return userEventMethods.join(', ').replace(/, ([a-zA-Z.]+)$/, ', or $1');

src/utils/resolve-to-testing-library-fn.ts

@@ -108,7 +108,7 @@ const resolveScope = (
 		const ref = currentScope.set.get(identifier);
 		if (ref && ref.defs.length > 0) {
 			const def = ref.defs[ref.defs.length - 1];
-			const importDetails = describePossibleImportDef(def);
+			const importDetails = def ? describePossibleImportDef(def) : null;
 
 			if (importDetails?.local === identifier) {
 				return importDetails;
@@ -159,6 +159,9 @@ export const resolveToTestingLibraryFn = <
 	if (!chain?.length) return null;
 
 	const identifier = chain[0];
+	if (!identifier) {
+		return null;
+	}
 	const scope = context.sourceCode.getScope(identifier);
 	const maybeImport = resolveScope(scope, getAccessorValue(identifier));
 

tests/rules/prefer-query-matchers.test.ts

@@ -100,7 +100,7 @@ const getInvalidAssertions = ({
 					messageId,
 					line: 7,
 					column: 10,
-					data: { query: validEntry.query, matcher: validEntry.matcher },
+					data: { query: validEntry?.query, matcher: validEntry?.matcher },
 				},
 			],
 		},
@@ -113,7 +113,7 @@ const getInvalidAssertions = ({
 					messageId,
 					line: 7,
 					column: 17,
-					data: { query: validEntry.query, matcher: validEntry.matcher },
+					data: { query: validEntry?.query, matcher: validEntry?.matcher },
 				},
 			],
 		},

tests/rules/prefer-user-event.test.ts

@@ -29,9 +29,11 @@ function createScenarioWithImport<
 const ruleTester = createRuleTester();
 
 function formatUserEventMethodsMessage(fireEventMethod: string): string {
-	const userEventMethods = MAPPING_TO_USER_EVENT[fireEventMethod].map(
-		(methodName) => `userEvent.${methodName}`
-	);
+	// TODO: refactor this using `Intl.ListFormat`
+	const userEventMethods =
+		MAPPING_TO_USER_EVENT[fireEventMethod]?.map(
+			(methodName) => `userEvent.${methodName}`
+		) ?? [];
 	let joinedList = '';
 
 	for (let i = 0; i < userEventMethods.length; i++) {

tests/test-utils.ts

@@ -9,7 +9,7 @@ const DEFAULT_TEST_CASE_CONFIG = {
 };
 
 class TestingLibraryRuleTester extends RuleTester {
-	run<TMessageIds extends string, TOptions extends readonly unknown[]>(
+	override run<TMessageIds extends string, TOptions extends readonly unknown[]>(
 		ruleName: string,
 		rule: TestingLibraryPluginRuleModule<TMessageIds, TOptions>,
 		{ invalid, valid }: RunTests<TMessageIds, TOptions>

tsconfig.json

@@ -1,14 +1,14 @@
 {
 	"compilerOptions": {
 		"strict": true,
+		"noUncheckedIndexedAccess": true,
+		"noImplicitOverride": true,
 		"target": "ES2023",
 		"module": "preserve",
 		// "moduleResolution": "Bundler", <-- this is implied by "module": "preserve"
 		"noEmit": true,
 		"lib": ["ES2023"],
 		"skipLibCheck": true,
-		"isolatedModules": true,
-		// TODO: turn it on
-		"noUncheckedIndexedAccess": false
+		"isolatedModules": true
 	}
 }