fix(core): Opt-out from optimizations if $item is used (#12036)

packages/@n8n/task-runner/src/js-task-runner/built-ins-parser/__tests__/built-ins-parser.test.ts

@@ -17,7 +17,7 @@ describe('BuiltInsParser', () => {
 	const parseAndExpectOk = (code: string) => {
 		const result = parser.parseUsedBuiltIns(code);
 		if (!result.ok) {
-			fail(result.error);
+			throw result.error;
 		}
 
 		return result.result;
@@ -151,6 +151,13 @@ describe('BuiltInsParser', () => {
 		});
 	});
 
+	describe('$item', () => {
+		it('should require all nodes and input when $item is used', () => {
+			const state = parseAndExpectOk('$item("0").$node["my node"].json["title"]');
+			expect(state).toEqual(new BuiltInsParserState({ needsAllNodes: true, needs$input: true }));
+		});
+	});
+
 	describe('ECMAScript syntax', () => {
 		describe('ES2020', () => {
 			it('should parse optional chaining', () => {

packages/@n8n/task-runner/src/js-task-runner/built-ins-parser/built-ins-parser.ts

@@ -125,6 +125,11 @@ export class BuiltInsParser {
 	private visitIdentifier = (node: Identifier, state: BuiltInsParserState) => {
 		if (node.name === '$env') {
 			state.markEnvAsNeeded();
+		} else if (node.name === '$item') {
+			// $item is legacy syntax that is basically an alias for WorkflowDataProxy
+			// and allows accessing any data. We need to support it for backwards
+			// compatibility, but we're not gonna implement any optimizations
+			state.markNeedsAllNodes();
 		} else if (
 			node.name === '$input' ||
 			node.name === '$json' ||