function _checkWhileConditions()

in src/grammar.ts [946:995]
45 lines of code
12 McCabe index (conditional complexity)

function _checkWhileConditions(grammar: Grammar, lineText: OnigString, isFirstLine: boolean, linePos: number, stack: StackElement, lineTokens: LineTokens): IWhileCheckResult {
	let anchorPosition = (stack.beginRuleCapturedEOL ? 0 : -1);
	const whileRules: IWhileStack[] = [];
	for (let node: StackElement | null = stack; node; node = node.pop()) {
		const nodeRule = node.getRule(grammar);
		if (nodeRule instanceof BeginWhileRule) {
			whileRules.push({
				rule: nodeRule,
				stack: node
			});
		}
	}

	for (let whileRule = whileRules.pop(); whileRule; whileRule = whileRules.pop()) {
		const { ruleScanner, findOptions } = prepareRuleWhileSearch(whileRule.rule, grammar, whileRule.stack.endRule, isFirstLine, linePos === anchorPosition);
		const r = ruleScanner.scanner.findNextMatchSync(lineText, linePos, findOptions);
		if (DebugFlags.InDebugMode) {
			console.log('  scanning for while rule');
			console.log(debugCompiledRuleToString(ruleScanner));
		}

		if (r) {
			const matchedRuleId = ruleScanner.rules[r.index];
			if (matchedRuleId !== -2) {
				// we shouldn't end up here
				stack = whileRule.stack.pop()!;
				break;
			}
			if (r.captureIndices && r.captureIndices.length) {
				lineTokens.produce(whileRule.stack, r.captureIndices[0].start);
				handleCaptures(grammar, lineText, isFirstLine, whileRule.stack, lineTokens, whileRule.rule.whileCaptures, r.captureIndices);
				lineTokens.produce(whileRule.stack, r.captureIndices[0].end);
				anchorPosition = r.captureIndices[0].end;
				if (r.captureIndices[0].end > linePos) {
					linePos = r.captureIndices[0].end;
					isFirstLine = false;
				}
			}
		} else {
			if (DebugFlags.InDebugMode) {
				console.log('  popping ' + whileRule.rule.debugName + ' - ' + whileRule.rule.debugWhileRegExp);
			}

			stack = whileRule.stack.pop()!;
			break;
		}
	}

	return { stack: stack, linePos: linePos, anchorPosition: anchorPosition, isFirstLine: isFirstLine };
}