Function diffLinesRaw

packages/jest-diff/src/diffLines.ts:166–207

(
  aLines: Array<string>,
  bLines: Array<string>,
)

// Compare two arrays of strings line-by-line.
export const diffLinesRaw = (
  aLines: Array<string>,
  bLines: Array<string>,
): Array<Diff> => {
  const aLength = aLines.length;
  const bLength = bLines.length;

  const isCommon = (aIndex: number, bIndex: number) =>
    aLines[aIndex] === bLines[bIndex];

  const diffs: Array<Diff> = [];
  let aIndex = 0;
  let bIndex = 0;

  const foundSubsequence = (
    nCommon: number,
    aCommon: number,
    bCommon: number,
  ) => {
    for (; aIndex !== aCommon; aIndex += 1) {
      diffs.push(new Diff(DIFF_DELETE, aLines[aIndex]));
    }
    for (; bIndex !== bCommon; bIndex += 1) {
      diffs.push(new Diff(DIFF_INSERT, bLines[bIndex]));
    }
    for (; nCommon !== 0; nCommon -= 1, aIndex += 1, bIndex += 1) {
      diffs.push(new Diff(DIFF_EQUAL, bLines[bIndex]));
    }
  };

  diff(aLength, bLength, isCommon, foundSubsequence);

  // After the last common subsequence, push remaining change items.
  for (; aIndex !== aLength; aIndex += 1) {
    diffs.push(new Diff(DIFF_DELETE, aLines[aIndex]));
  }
  for (; bIndex !== bLength; bIndex += 1) {
    diffs.push(new Diff(DIFF_INSERT, bLines[bIndex]));
  }

  return diffs;
};