Function generateCodeFrame

packages/vite/src/node/utils.ts:489–567

(
  source: string,
  start: number | Pos = 0,
  end?: number | Pos,
)

const ELLIPSIS = '...'

export function generateCodeFrame(
  source: string,
  start: number | Pos = 0,
  end?: number | Pos,
): string {
  start = Math.max(posToNumber(source, start), 0)
  end = Math.min(
    end !== undefined ? posToNumber(source, end) : start,
    source.length,
  )
  const lastPosLine =
    end !== undefined
      ? numberToPos(source, end).line
      : numberToPos(source, start).line + range
  const lineNumberWidth = Math.max(3, String(lastPosLine).length + 1)
  const lines = source.split(splitRE)
  let count = 0
  const res: string[] = []
  for (let i = 0; i < lines.length; i++) {
    count += lines[i].length
    if (count >= start) {
      for (let j = i - range; j <= i + range || end > count; j++) {
        if (j < 0 || j >= lines.length) continue
        const line = j + 1
        const lineLength = lines[j].length
        const pad = Math.max(start - (count - lineLength), 0)
        const underlineLength = Math.max(
          1,
          end > count ? lineLength - pad : end - start,
        )

        let displayLine = lines[j]
        let underlinePad = pad
        if (lineLength > MAX_DISPLAY_LEN) {
          let startIdx = 0
          if (j === i) {
            if (underlineLength > MAX_DISPLAY_LEN) {
              startIdx = pad
            } else {
              const center = pad + Math.floor(underlineLength / 2)
              startIdx = Math.max(0, center - Math.floor(MAX_DISPLAY_LEN / 2))
            }
            underlinePad =
              Math.max(0, pad - startIdx) + (startIdx > 0 ? ELLIPSIS.length : 0)
          }
          const prefix = startIdx > 0 ? ELLIPSIS : ''
          const suffix = lineLength - startIdx > MAX_DISPLAY_LEN ? ELLIPSIS : ''
          const sliceLen = MAX_DISPLAY_LEN - prefix.length - suffix.length
          displayLine =
            prefix + displayLine.slice(startIdx, startIdx + sliceLen) + suffix
        }
        res.push(
          `${line}${' '.repeat(lineNumberWidth - String(line).length)}|  ${displayLine}`,
        )
        if (j === i) {
          // push underline
          const underline = '^'.repeat(
            Math.min(underlineLength, MAX_DISPLAY_LEN),