Function addLineNumbers

src/utils/file.ts:290–319

({
  content,
  // 1-indexed
  startLine,
}: {
  content: string
  startLine: number
})

 * Adds cat -n style line numbers to the content.
 */
export function addLineNumbers({
  content,
  // 1-indexed
  startLine,
}: {
  content: string
  startLine: number
}): string {
  if (!content) {
    return ''
  }

  const lines = content.split(/\r?\n/)

  if (isCompactLinePrefixEnabled()) {
    return lines
      .map((line, index) => `${index + startLine}\t${line}`)
      .join('\n')
  }

  return lines
    .map((line, index) => {
      const numStr = String(index + startLine)
      if (numStr.length >= 6) {
        return `${numStr}→${line}`
      }
      return `${numStr.padStart(6, ' ')}→${line}`
    })
    .join('\n')
}

/**
 * Inverse of addLineNumbers — strips the `N→` or `N\t` prefix from a single