src/compiler/utils/get_code_frame.ts


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function tabs_to_spaces(str: string) {
  return str.replace(/^\t+/, (match) => match.split('\t').join('  '));
}

export default function get_code_frame(source: string, line: number, column: number) {
  const lines = source.split('\n');

  const frame_start = Math.max(0, line - 2);
  const frame_end = Math.min(line + 3, lines.length);

  const digits = String(frame_end + 1).length;

  return lines
    .slice(frame_start, frame_end)
    .map((str, i) => {
      const isErrorLine = frame_start + i === line;
      const line_num = String(i + frame_start + 1).padStart(digits, ' ');

      if (isErrorLine) {
        const indicator = ' '.repeat(digits + 2 + tabs_to_spaces(str.slice(0, column)).length) + '^';
        return `${line_num}: ${tabs_to_spaces(str)}\n${indicator}`;
      }

      return `${line_num}: ${tabs_to_spaces(str)}`;
    })
    .join('\n');
}