astro/dist/core/errors/printer.js

Astro is a modern site builder with web best practices, performance, and DX front-of-mind.

import { normalizeLF } from "./utils.js";
/** Generate a code frame from string and an error location */
export function codeFrame(src, loc) {
	if (!loc || loc.line === undefined || loc.column === undefined) {
		return "";
	}
	const lines = normalizeLF(src).split("\n").map((ln) => ln.replace(/\t/g, "  "));
	// grab 2 lines before, and 3 lines after focused line
	const visibleLines = [];
	for (let n = -2; n <= 2; n++) {
		if (lines[loc.line + n]) visibleLines.push(loc.line + n);
	}
	// figure out gutter width
	let gutterWidth = 0;
	for (const lineNo of visibleLines) {
		let w = `> ${lineNo}`;
		if (w.length > gutterWidth) gutterWidth = w.length;
	}
	// print lines
	let output = "";
	for (const lineNo of visibleLines) {
		const isFocusedLine = lineNo === loc.line - 1;
		output += isFocusedLine ? "> " : "  ";
		output += `${lineNo + 1} | ${lines[lineNo]}\n`;
		if (isFocusedLine) output += `${Array.from({ length: gutterWidth }).join(" ")}  | ${Array.from({ length: loc.column }).join(" ")}^\n`;
	}
	return output;
}