in server/src/diff.ts [856:934]
private PrettifyChanges(changes: DiffChange[]): DiffChange[] {
// Shift all the changes down first
for (let i = 0; i < changes.length; i++) {
const change = changes[i];
const originalStop = (i < changes.length - 1) ? changes[i + 1].originalStart : this._originalElementsOrHash.length;
const modifiedStop = (i < changes.length - 1) ? changes[i + 1].modifiedStart : this._modifiedElementsOrHash.length;
const checkOriginal = change.originalLength > 0;
const checkModified = change.modifiedLength > 0;
while (change.originalStart + change.originalLength < originalStop &&
change.modifiedStart + change.modifiedLength < modifiedStop &&
(!checkOriginal || this.OriginalElementsAreEqual(change.originalStart, change.originalStart + change.originalLength)) &&
(!checkModified || this.ModifiedElementsAreEqual(change.modifiedStart, change.modifiedStart + change.modifiedLength))) {
change.originalStart++;
change.modifiedStart++;
}
let mergedChangeArr: Array<DiffChange | null> = [null];
if (i < changes.length - 1 && this.ChangesOverlap(changes[i], changes[i + 1], mergedChangeArr)) {
changes[i] = mergedChangeArr[0]!;
changes.splice(i + 1, 1);
i--;
continue;
}
}
// Shift changes back up until we hit empty or whitespace-only lines
for (let i = changes.length - 1; i >= 0; i--) {
const change = changes[i];
let originalStop = 0;
let modifiedStop = 0;
if (i > 0) {
const prevChange = changes[i - 1];
if (prevChange.originalLength > 0) {
originalStop = prevChange.originalStart + prevChange.originalLength;
}
if (prevChange.modifiedLength > 0) {
modifiedStop = prevChange.modifiedStart + prevChange.modifiedLength;
}
}
const checkOriginal = change.originalLength > 0;
const checkModified = change.modifiedLength > 0;
let bestDelta = 0;
let bestScore = this._boundaryScore(change.originalStart, change.originalLength, change.modifiedStart, change.modifiedLength);
for (let delta = 1; ; delta++) {
const originalStart = change.originalStart - delta;
const modifiedStart = change.modifiedStart - delta;
if (originalStart < originalStop || modifiedStart < modifiedStop) {
break;
}
if (checkOriginal && !this.OriginalElementsAreEqual(originalStart, originalStart + change.originalLength)) {
break;
}
if (checkModified && !this.ModifiedElementsAreEqual(modifiedStart, modifiedStart + change.modifiedLength)) {
break;
}
const score = this._boundaryScore(originalStart, change.originalLength, modifiedStart, change.modifiedLength);
if (score > bestScore) {
bestScore = score;
bestDelta = delta;
}
}
change.originalStart -= bestDelta;
change.modifiedStart -= bestDelta;
}
return changes;
}