Function joinAlignedDiffsNoExpand

packages/jest-diff/src/joinAlignedDiffs.ts:112–283

(
  diffs: Array<Diff>,
  options: DiffOptionsNormalized,
)

// Given array of aligned strings with inverse highlight formatting,
// return joined lines with diff formatting (and patch marks, if needed).
export const joinAlignedDiffsNoExpand = (
  diffs: Array<Diff>,
  options: DiffOptionsNormalized,
): string => {
  const iLength = diffs.length;
  const nContextLines = options.contextLines;
  const nContextLines2 = nContextLines + nContextLines;

  // First pass: count output lines and see if it has patches.
  let jLength = iLength;
  let hasExcessAtStartOrEnd = false;
  let nExcessesBetweenChanges = 0;
  let i = 0;
  while (i !== iLength) {
    const iStart = i;
    while (i !== iLength && diffs[i][0] === DIFF_EQUAL) {
      i += 1;
    }

    if (iStart !== i) {
      if (iStart === 0) {
        // at start
        if (i > nContextLines) {
          jLength -= i - nContextLines; // subtract excess common lines
          hasExcessAtStartOrEnd = true;
        }
      } else if (i === iLength) {
        // at end
        const n = i - iStart;
        if (n > nContextLines) {
          jLength -= n - nContextLines; // subtract excess common lines
          hasExcessAtStartOrEnd = true;
        }
      } else {
        // between changes
        const n = i - iStart;
        if (n > nContextLines2) {
          jLength -= n - nContextLines2; // subtract excess common lines
          nExcessesBetweenChanges += 1;
        }
      }
    }

    while (i !== iLength && diffs[i][0] !== DIFF_EQUAL) {
      i += 1;
    }
  }

  const hasPatch = nExcessesBetweenChanges !== 0 || hasExcessAtStartOrEnd;
  if (nExcessesBetweenChanges !== 0) {
    jLength += nExcessesBetweenChanges + 1; // add patch lines
  } else if (hasExcessAtStartOrEnd) {
    jLength += 1; // add patch line
  }
  const jLast = jLength - 1;

  const lines: Array<string> = [];