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diff files line-by-line instead of character-by-character (#10344)
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* use our diff implementation for history

* use dmp format
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@riknoll
riknoll authored Jan 17, 2025
1 parent 897f764 commit 955518b
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Showing 5 changed files with 252 additions and 47 deletions.
2 changes: 1 addition & 1 deletion pxtblocks/diff.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -461,7 +461,7 @@ export function decompiledDiffAsync(oldTs: string, oldResp: pxtc.CompileResult,
log(newXml);

// compute diff of typescript sources
const diffLines = pxt.diff.compute(oldTs, newTs, {
const diffLines = pxt.diff.computeFormattedDiff(oldTs, newTs, {
ignoreWhitespace: true,
full: true
});
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204 changes: 167 additions & 37 deletions pxtlib/diff.ts
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,8 +20,27 @@ namespace pxt.diff {

type UArray = Uint32Array | Uint16Array

export function toLines(file: string) {
return file ? file.split(/\r?\n/) : []
export function toLines(file: string, includeNewline?: boolean) {
if (!file) return [];

if (includeNewline) {
const result: string[] = [];

let lineStart = 0;
for (let i = 0; i < file.length; i++) {
const current = file.charAt(i);
if (current === "\n") {
result.push(file.substring(lineStart, i + 1));
lineStart = i + 1;
}
}

result.push(file.substring(lineStart));

return result;
}

return file.split(/\r?\n/);
}

export interface DiffOptions {
Expand All @@ -31,15 +50,35 @@ namespace pxt.diff {
full?: boolean; // don't try to create short diff
}

enum DiffOp {
Added = 1,
Deleted = -1,
Unchanged = 0
}

type DiffPart = [DiffOp, string];

// This is the format used by Google's diff-match-patch library, which we used
// to use. Our diffs match this format but we don't use the start2 and length2
// properties or include deletions in the diffs since our patches are meant to
// be one-way only
interface Patch {
diffs: DiffPart[];
length1: number;
length2?: number;
start1: number;
start2?: number;
}

// based on An O(ND) Difference Algorithm and Its Variations by EUGENE W. MYERS
export function compute(fileA: string, fileB: string, options: DiffOptions = {}): string[] {
export function compute(fileA: string, fileB: string, options: DiffOptions = {}): DiffPart[] {
if (options.ignoreWhitespace) {
fileA = fileA.replace(/[\r\n]+$/, "")
fileB = fileB.replace(/[\r\n]+$/, "")
}

const a = toLines(fileA)
const b = toLines(fileB)
const a = toLines(fileA, true);
const b = toLines(fileB, true);

const MAX = Math.min(options.maxDiffSize || 1024, a.length + b.length)
if (MAX == 0) // nothing to diff
Expand Down Expand Up @@ -89,7 +128,7 @@ namespace pxt.diff {
break
}

const diff: string[] = []
const diff: DiffPart[] = []
let k = endpoint
for (let D = trace.length - 1; D >= 0; D--) {
const V = trace[D]
Expand All @@ -105,27 +144,54 @@ namespace pxt.diff {
let y = x - k
const snakeLen = V[MAX + k] - x
for (let i = snakeLen - 1; i >= 0; --i)
diff.push(" " + b[y + i])
diff.push([DiffOp.Unchanged, b[y + i]])

if (nextK == k - 1) {
diff.push("- " + a[x - 1])
diff.push([DiffOp.Deleted, a[x - 1]])
} else {
if (y > 0)
diff.push("+ " + b[y - 1])
diff.push([DiffOp.Added, b[y - 1]])
}
k = nextK
}
diff.reverse()

if (options.context == Infinity || options.full)
return diff
return diff;

function computeFor(D: number, V: UArray) {
for (let k = -D; k <= D; k += 2) {
let x = 0
if (k == -D || (k != D && V[MAX + k - 1] < V[MAX + k + 1]))
x = V[MAX + k + 1]
else
x = V[MAX + k - 1] + 1
let y = x - k
while (x < aidx.length && y < bidx.length && aidx[x] == bidx[y]) {
x++
y++
}
V[MAX + k] = x
if (x >= aidx.length && y >= bidx.length) {
return k
}
}
return null
}
}

export function computeFormattedDiff(fileA: string, fileB: string, options: DiffOptions = {}): string[] {
const diff = compute(fileA, fileB, options);

if (options.context == Infinity || options.full) {
return diff.map(formatEdit);
}

let aline = 1, bline = 1, idx = 0
const shortDiff: string[] = []
const context = options.context || 3
while (idx < diff.length) {
let nextIdx = idx
while (nextIdx < diff.length && diff[nextIdx][0] == " ")
while (nextIdx < diff.length && diff[nextIdx][0] === DiffOp.Unchanged)
nextIdx++
if (nextIdx == diff.length)
break
Expand All @@ -143,7 +209,7 @@ namespace pxt.diff {
let endIdx = idx
let numCtx = 0
while (endIdx < diff.length) {
if (diff[endIdx][0] == " ") {
if (diff[endIdx][0] === DiffOp.Unchanged) {
numCtx++
if (numCtx > context * 2 + 2) {
endIdx -= context + 2
Expand All @@ -156,39 +222,103 @@ namespace pxt.diff {
}

while (idx < endIdx) {
shortDiff.push(diff[idx])
shortDiff.push(formatEdit(diff[idx]))
const c = diff[idx][0]
switch (c) {
case "-": aline++; break;
case "+": bline++; break;
case " ": aline++; bline++; break;
case DiffOp.Deleted: aline++; break;
case DiffOp.Added: bline++; break;
case DiffOp.Unchanged: aline++; bline++; break;
}
idx++
}
shortDiff[hdPos] = `@@ -${aline0},${aline - aline0} +${bline0},${bline - bline0} @@`
}

return shortDiff
}

function computeFor(D: number, V: UArray) {
for (let k = -D; k <= D; k += 2) {
let x = 0
if (k == -D || (k != D && V[MAX + k - 1] < V[MAX + k + 1]))
x = V[MAX + k + 1]
else
x = V[MAX + k - 1] + 1
let y = x - k
while (x < aidx.length && y < bidx.length && aidx[x] == bidx[y]) {
x++
y++
function formatEdit([change, text]: DiffPart): string {
let result: string;
if (change === DiffOp.Added) {
result = "+ ";
}
else if (change === DiffOp.Deleted) {
result = "- ";
}
else {
result = " ";
}

return result + text.replace(/\r?n/, "");
}

function diffToPatch(diff: DiffPart[]): Patch[] {
const linePatches: Patch[] = [];

let patchedText = "";
let currentAddition = "";
let currentDeletion = "";
let prevOp = DiffOp.Unchanged;

const pushEdit = () => {
linePatches.push({
start1: patchedText.length,
length1: currentDeletion.length,
diffs: [[DiffOp.Added, currentAddition]]
});
patchedText += currentAddition;
currentAddition = "";
currentDeletion = "";
};

for (let i = 0; i < diff.length; i++) {
const [op, line] = diff[i];

if (op == DiffOp.Unchanged) {
if (prevOp !== DiffOp.Unchanged) {
pushEdit();
}
V[MAX + k] = x
if (x >= aidx.length && y >= bidx.length) {
return k
patchedText += line
}
else if (op === DiffOp.Added) {
currentAddition += line
}
else if (op === DiffOp.Deleted) {
if (prevOp === DiffOp.Added) {
pushEdit();
}
currentDeletion += line
}
return null

prevOp = op;
}

if (prevOp !== DiffOp.Unchanged) {
pushEdit();
}

return linePatches;
}

export function computePatch(fileA: string, fileB: string): Patch[] {
const diff = compute(fileA, fileB, { full: true });
const patch = diffToPatch(diff);

return patch
}

export function applyPatch(file: string, patch: Patch[]) {
let result = file;

for (const part of patch) {
const newText = part.diffs.filter(d => d[0] !== DiffOp.Deleted).map(d => d[1]).join("");
result =
result.substring(0, part.start1) +
newText +
result.substring(part.start1 + part.length1);
}

return result;
}

// based on "A Formal Investigation of Diff3" by Sanjeev Khanna, Keshav Kunal, and Benjamin C. Pierce
Expand Down Expand Up @@ -265,12 +395,12 @@ namespace pxt.diff {

// pxt.log(da)
for (let l of da) {
if (l[0] == "+") {
if (l[0] == DiffOp.Added) {
aidx++
} else if (l[0] == "-") {
} else if (l[0] == DiffOp.Deleted) {
ma[oidx] = null
oidx++
} else if (l[0] == " ") {
} else if (l[0] == DiffOp.Unchanged) {
ma[oidx] = aidx
aidx++
oidx++
Expand Down Expand Up @@ -331,7 +461,7 @@ namespace pxt.diff {
}

export function render(fileA: string, fileB: string, options: RenderOptions = {}): HTMLElement {
const diffLines = compute(fileA, fileB, options);
const diffLines = computeFormattedDiff(fileA, fileB, options);
if (!diffLines) {
return pxt.dom.el("div", null, pxtc.Util.lf("Too many differences to render diff."));
}
Expand Down Expand Up @@ -400,7 +530,7 @@ namespace pxt.diff {
}

function lineDiff(lineA: string, lineB: string): { a: HTMLElement, b: HTMLElement } {
const df = compute(lineA.split("").join("\n"), lineB.split("").join("\n"), {
const df = computeFormattedDiff(lineA.split("").join("\n"), lineB.split("").join("\n"), {
context: Infinity
})
if (!df) // diff failed
Expand Down
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