tests/test.sh exit code (0 → resolved); the classification below is post-hoc and cannot change it./home/user/instruction.md
1 # Implement the line diff (minimal canonical edit script) 2 3 ## Context 4 `diff-patch-engine` is the line-level diff/patch building block behind our 5 `git diff`-style tooling and three-way merges (TypeScript, Node 20). It computes 6 an ordered edit script between two sequences of lines and can replay that script 7 onto the original to reproduce the target. 8 9 `applyPatch(original, edits)` (the diff's own verifier), `diffStats`, and the 10 `splitLines` / `joinLines` text helpers are all provided and must not be 11 changed. **Only `diff(a, b)` is unimplemented.** 12 13 ## Your task 14 Implement `src/diff/myers.ts` → `diff(a: string[], b: string[]): Edit[]`, 15 returning an ordered list of `eq` / `del` / `ins` edits (see `Edit` / `EditOp` 16 in `types.ts`). The returned script is graded against three independent 17 properties , **validity**, **minimality**, and a **canonical tie-break** , and 18 must satisfy all three for every input. Being valid and minimal is *not* 19 sufficient: a uniquely determined script is required and any other minimal 20 script is graded wrong. 21 22 Each op consumes lines as follows: an `eq` consumes one line from each side and 23 those two lines are equal; a `del` consumes one line from `a`; an `ins` consumes 24 one line from `b`. 25 26 ### 1. Validity 27 `applyPatch(a, diff(a, b))` must deep-equal `b`. Equivalently, both of these 28 hold simultaneously: 29 - the subsequence of `eq` + `del` lines, in order, equals `a`; 30 - the subsequence of `eq` + `ins` lines, in order, equals `b`; 31 32 and every `eq` carries a line equal to the line it consumes on each side. 33 34 ### 2. Minimality 35 Among all valid scripts, the returned one must use the fewest non-`eq` ops. Let 36 `C(a, b)` be the maximum possible number of `eq` ops over all valid scripts for 37 the pair (equivalently, the length of the longest common subsequence of `a` and 38 `b`). Then the script must have exactly `C(a, b)` `eq` ops and exactly 39 `a.length + b.length - 2 * C(a, b)` non-`eq` ops (`del` + `ins`). This is what 40 makes the result a *diff* rather than "delete all of `a`, then insert all of 41 `b`". 42 43 ### 3. Canonical tie-break (the crux) 44 Many distinct valid, minimal scripts can exist for one pair. Exactly one of them 45 is canonical, and that is the one you must return. The canonical script is the 46 unique valid, minimal script characterised by the following property, applied to 47 the script read left to right. 48 49 > Consider the script as a left-to-right interleaving of `a` and `b`. Walk a 50 > pair of cursors `(i, j)` , `i` into `a`, `j` into `b` , both starting at the 51 > first line. At each step the next op of the script decides which cursor(s) 52 > advance: `del` advances `i`, `ins` advances `j`, `eq` advances both (and 53 > requires `a[i] === b[j]`). 54 > 55 > Call an op **length-preserving at `(i, j)`** if the script can still be 56 > completed, from the resulting cursor position, into a valid script that meets 57 > the minimality bound of clause 2 for the whole pair. The canonical script is 58 > the one that, at every step, makes the **highest-priority length-preserving 59 > choice** under this fixed priority order: 60 > 61 > 1. `del` of `a[i]` , chosen whenever it is length-preserving at `(i, j)`; 62 > 2. otherwise `ins` of `b[j]` , chosen whenever it is length-preserving at 63 > `(i, j)`; 64 > 3. otherwise `eq` of the shared line (this case forces `a[i] === b[j]`). 65 > 66 > When `i` has reached the end of `a`, only `ins` remains; when `j` has reached 67 > the end of `b`, only `del` remains; when both are at the end, the script ends. 68 69 The grader pins this exact script; any other valid, minimal, but 70 differently-resolved script is rejected. 71 72 ## Edge cases to get right 73 - `a` and `b` equal → all `eq`, no `del`/`ins`. 74 - `a` empty → every line of `b` as `ins`, in order. 75 - `b` empty → every line of `a` as `del`, in order. 76 - both empty (`[]`) → `[]`. 77 - Lines are compared by exact string equality only , no Unicode normalization, 78 no trimming. Lines containing whitespace, tabs, emoji, combining characters, 79 newline characters, or text that looks like an op name are opaque values. 80 - Callers diffing text use `splitLines`, so a trailing newline appears as a 81 final `""` entry and must be preserved verbatim. The empty string is `[""]` 82 (length 1), never `[]`. 83 - The same `(a, b)` must always produce the identical script (determinism). 84 85 ## Performance & memory 86 Inputs can be large , up to ~100,000 lines , and are frequently *largely 87 identical*: two revisions of the same file, sharing long common runs at the 88 start, the end, or both. Your implementation must use memory **proportional to 89 the input size** on such inputs. Allocating a full `n × m` dynamic-programming 90 table is `Θ(n·m)` memory and will **exhaust the available memory on large 91 inputs , that is graded as a failure**. The constraint only bites at scale: 92 small inputs may be handled however you like. Time should stay within a few 93 seconds even for the largest inputs. 94 95 ## Definition of done 96 `npm run typecheck` is clean and `npm test` passes. Implement `diff` only , do 97 not modify `applyPatch`, the text helpers, the types/errors, or the tests. 98
/home/user/app/src/diff/myers.ts
1 import type { Edit } from "./types.js";
2
3 /**
4 * Compute the canonical minimal line-level edit script transforming `a` into `b`.
5 *
6 * Return an ordered `Edit[]` that, replayed against `a` by `applyPatch`,
7 * reproduces `b`. An `eq` consumes one line from each side (the lines are
8 * equal); a `del` consumes one line from `a`; an `ins` consumes one line from
9 * `b`. (See `EditOp` in types.ts.) The script must satisfy ALL THREE of the
10 * following; each is checked independently and validity + minimality is NOT
11 * sufficient.
12 *
13 * 1. VALID , `applyPatch(a, diff(a, b))` deep-equals `b`. Equivalently the
14 * `eq`+`del` lines (in order) equal `a`, the `eq`+`ins` lines equal `b`, and
15 * every `eq` carries a line equal to the one it consumes on each side.
16 * 2. MINIMAL , fewest non-`eq` ops of any valid script. With `C(a,b)` = the
17 * maximum achievable number of `eq` ops (the LCS length), the script has
18 * exactly `C(a,b)` `eq` ops and `a.length + b.length - 2*C(a,b)` non-`eq` ops.
19 * 3. CANONICAL , among the (often many) valid minimal scripts, return THE one
20 * defined below; the same `(a,b)` always yields it.
21 *
22 * The canonical script (the crux): read it left to right as an interleaving of
23 * `a` and `b`, walking cursors `(i, j)` from the start , `del` advances `i`,
24 * `ins` advances `j`, `eq` advances both (and requires `a[i] === b[j]`). Call an
25 * op *length-preserving at `(i, j)`* if, after taking it, the script can still be
26 * completed from the new position into a valid script meeting the clause-2
27 * minimality bound. At every step take the highest-priority length-preserving
28 * choice under this fixed priority:
29 * (1) `del` of `a[i]` if length-preserving at `(i, j)`;
30 * (2) else `ins` of `b[j]` if length-preserving at `(i, j)`;
31 * (3) else `eq` of the shared line (this case forces `a[i] === b[j]`).
32 * When `i` is at the end of `a` only `ins` remains; when `j` is at the end of
33 * `b` only `del` remains; when both are at the end the script ends.
34 *
35 * Edge cases: equal inputs -> all `eq`; empty `a` -> all `ins`; empty `b` -> all
36 * `del`; both empty -> `[]`. Lines compare by exact string equality only (no
37 * normalization/trimming); whitespace, tabs, emoji, combining chars and embedded
38 * newlines are opaque. A trailing newline shows up via `splitLines` as a final
39 * `""` and must be preserved; the empty string is `[""]` (length 1), never `[]`.
40 *
41 * Performance & memory: inputs may be large (up to ~1e5 lines) and are often
42 * largely identical (long shared runs at the start and/or end). Use memory
43 * proportional to the input size , allocating a full `n*m` table (Θ(n·m) memory)
44 * exhausts memory on large inputs and is graded as a failure. Small inputs may
45 * be handled any way; the constraint only bites at scale.
46 */
47 export function diff(a: string[], b: string[]): Edit[] {
48 // TODO(diff): implement the contract documented above. This stub throws so the
49 // engine is wired but non-functional; the suite must fail until implemented.
50 void a;
51 void b;
52 throw new Error("diff not implemented");
53 }
54/home/user/app/src/diff/types.ts
1 /**
2 * Types for the line-oriented diff + patch engine.
3 *
4 * A diff is an **edit script**: an ordered list of operations that, replayed
5 * against the original sequence of lines, reproduces the target sequence.
6 *
7 * - `eq` , a line present in BOTH sides; consumes one line from the original
8 * and one from the target (they are equal).
9 * - `del` , a line present only in the original; consumes one line from the
10 * original (it is removed).
11 * - `ins` , a line present only in the target; consumes one line from the
12 * target (it is added).
13 *
14 * The engine works on `string[]` (one entry per line); {@link splitLines} /
15 * {@link joinLines} convert to and from a single text blob.
16 */
17
18 export type EditOp = "eq" | "del" | "ins";
19
20 /** A single edit-script entry: an operation paired with the line it concerns. */
21 export interface Edit {
22 op: EditOp;
23 /** For `eq`/`del` this is the original line; for `ins` it is the new line. */
24 line: string;
25 }
26
27 /** Aggregate counts over an edit script (handy for tests and stats). */
28 export interface DiffStats {
29 eq: number;
30 del: number;
31 ins: number;
32 }
33ls -la /home/user/app/src/diff/ && echo "---" && cat /home/user/app/package.json && echo "---INDEX---" && ls /home/user/app/src/diff/
total 20
drwxr-xr-x 2 user user 128 Jun 20 08:36 .
drwxr-xr-x 3 user user 60 Jun 19 22:50 ..
-rw-r--r-- 1 user user 538 Jun 17 20:27 errors.ts
-rw-r--r-- 1 user user 3129 Jun 20 08:46 myers.ts
-rw-r--r-- 1 user user 2886 Jun 17 20:27 patch.ts
-rw-r--r-- 1 user user 528 Jun 17 20:27 text.ts
-rw-r--r-- 1 user user 1127 Jun 17 20:27 types.ts
---
{
"name": "diff-patch-engine",
"version": "0.2.0",
"private": true,
"description": "Line-oriented diff (minimal LCS edit script) and patch-apply engine.",
"type": "module",
"engines": {
"node": ">=20"
},
"scripts": {
"build": "tsc -p tsconfig.json",
"typecheck": "tsc -p tsconfig.json --noEmit",
"test": "vitest run",
"test:watch": "vitest"
},
"devDependencies": {
"@types/node": "20.14.10",
"typescript": "5.5.3",
"vitest": "1.6.0"
}
}
---INDEX---
errors.ts
myers.ts
patch.ts
text.ts
types.ts/home/user/app/src/diff/patch.ts
1 import { PatchError } from "./errors.js";
2 import type { DiffStats, Edit } from "./types.js";
3
4 /**
5 * Apply an edit script to `original`, returning the patched line sequence.
6 *
7 * Replays the script left to right against a cursor into `original`:
8 *
9 * - `eq` , the next original line must EQUAL `edit.line`; emit it and advance
10 * the cursor. A mismatch (or running off the end) is a
11 * `PatchError("context_mismatch" | "unexpected_end")`: the patch does not
12 * apply to this input.
13 * - `del` , the next original line must equal `edit.line`; advance the cursor
14 * WITHOUT emitting (the line is removed). Same error rules as `eq`.
15 * - `ins` , emit `edit.line`; the cursor does NOT advance (nothing consumed
16 * from the original).
17 *
18 * After the script, every original line must have been consumed; leftover lines
19 * are a `PatchError("trailing_lines")`. An unrecognised op is
20 * `PatchError("unknown_op")`.
21 *
22 * This is the inverse of {@link diff}: for any `a`, `b`,
23 * `applyPatch(a, diff(a, b))` must deep-equal `b`. Provided complete , the diff
24 * you implement is validated against this applier.
25 */
26 export function applyPatch(original: string[], edits: Edit[]): string[] {
27 const out: string[] = [];
28 let i = 0; // cursor into `original`
29
30 for (const edit of edits) {
31 switch (edit.op) {
32 case "eq": {
33 if (i >= original.length) {
34 throw new PatchError("unexpected_end", `eq past end of original at op consuming "${edit.line}"`);
35 }
36 if (original[i] !== edit.line) {
37 throw new PatchError(
38 "context_mismatch",
39 `eq mismatch at original line ${i}: expected "${edit.line}", found "${original[i]}"`,
40 );
41 }
42 out.push(original[i] as string);
43 i++;
44 break;
45 }
46 case "del": {
47 if (i >= original.length) {
48 throw new PatchError("unexpected_end", `del past end of original at op removing "${edit.line}"`);
49 }
50 if (original[i] !== edit.line) {
51 throw new PatchError(
52 "context_mismatch",
53 `del mismatch at original line ${i}: expected "${edit.line}", found "${original[i]}"`,
54 );
55 }
56 i++;
57 break;
58 }
59 case "ins": {
60 out.push(edit.line);
61 break;
62 }
63 default: {
64 throw new PatchError("unknown_op", `unknown edit op: ${String((edit as Edit).op)}`);
65 }
66 }
67 }
68
69 if (i !== original.length) {
70 throw new PatchError(
71 "trailing_lines",
72 `patch consumed ${i} of ${original.length} original lines; ${original.length - i} left over`,
73 );
74 }
75 return out;
76 }
77
78 /** Tally an edit script by op kind. Provided complete. */
79 export function diffStats(edits: Edit[]): DiffStats {
80 const stats: DiffStats = { eq: 0, del: 0, ins: 0 };
81 for (const e of edits) stats[e.op]++;
82 return stats;
83 }
84/home/user/app/src/diff/text.ts
1 /**
2 * Text <-> lines conversion for the diff engine.
3 *
4 * `splitLines` splits on "\n" and keeps every line as a separate entry. A
5 * trailing newline yields a final empty entry preserved by `joinLines`, so the
6 * round-trip `joinLines(splitLines(t)) === t` holds for any input (including the
7 * empty string, which becomes `[""]`).
8 *
9 * Provided complete.
10 */
11 export function splitLines(text: string): string[] {
12 return text.split("\n");
13 }
14
15 export function joinLines(lines: string[]): string {
16 return lines.join("\n");
17 }
18cat tsconfig.json && echo "---" && ls node_modules/.bin/ | grep -E "tsx|ts-node|vitest|tsc" && echo "---vitest config---" && (cat vitest.config.* 2>/dev/null || echo none) && echo "---tests dir---" && ls -R test tests __tests__ 2>/dev/null | head -50
{
"compilerOptions": {
"target": "ES2022",
"module": "ESNext",
"moduleResolution": "Bundler",
"lib": ["ES2022"],
"types": ["node"],
"rootDir": ".",
"outDir": "dist",
"strict": true,
"noUnusedLocals": true,
"noUnusedParameters": true,
"noImplicitReturns": true,
"noFallthroughCasesInSwitch": true,
"exactOptionalPropertyTypes": false,
"esModuleInterop": true,
"forceConsistentCasingInFileNames": true,
"resolveJsonModule": true,
"skipLibCheck": true,
"verbatimModuleSyntax": false
},
"include": ["src", "test"],
"exclude": ["node_modules", "dist"]
}
---
tsc
vitest
---vitest config---
import { defineConfig } from "vitest/config";
export default defineConfig({
test: {
environment: "node",
include: ["test/**/*.test.ts"],
reporters: ["default"],
testTimeout: 10_000,
hookTimeout: 10_000,
},
});
---tests dir---
test:
patch.test.ts/home/user/app/test/patch.test.ts
1 import { describe, expect, it } from "vitest";
2 import { applyPatch } from "../src/diff/patch.js";
3 import { PatchError } from "../src/diff/errors.js";
4 import type { Edit } from "../src/diff/types.js";
5
6 const E = (op: Edit["op"], line: string): Edit => ({ op, line });
7
8 // applyPatch is provided/complete; one round-trip + one error-path sanity is
9 // enough here. The diff suite exercises applyPatch heavily on every assertion.
10 describe("applyPatch (provided)", () => {
11 it("replays eq/del/ins to reconstruct the target", () => {
12 const original = ["a", "b", "c"];
13 const edits: Edit[] = [E("eq", "a"), E("del", "b"), E("ins", "x"), E("eq", "c")];
14 expect(applyPatch(original, edits)).toEqual(["a", "x", "c"]);
15 });
16
17 it("throws trailing_lines when the script leaves original lines unconsumed", () => {
18 try {
19 applyPatch(["a", "b"], [E("eq", "a")]);
20 throw new Error("expected throw");
21 } catch (err) {
22 expect((err as PatchError).code).toBe("trailing_lines");
23 }
24 });
25 });
26import type { Edit } from "./types.js";
/**
* Compute the canonical minimal line-level edit script transforming `a` into `b`.
*
* Return an ordered `Edit[]` that, replayed against `a` by `applyPatch`,
* reproduces `b`. An `eq` consumes one line from each side (the lines are
* equal); a `del` consumes one line from `a`; an `ins` consumes one line from
* `b`. (See `EditOp` in types.ts.) The script must satisfy ALL THREE of the
* following; each is checked independently and validity + minimality is NOT
* sufficient.
*
* 1. VALID , `applyPatch(a, diff(a, b))` deep-equals `b`. Equivalently the
* `eq`+`del` lines (in order) equal `a`, the `eq`+`ins` lines equal `b`, and
* every `eq` carries a line equal to the one it consumes on each side.
* 2. MINIMAL , fewest non-`eq` ops of any valid script. With `C(a,b)` = the
* maximum achievable number of `eq` ops (the LCS length), the script has
* exactly `C(a,b)` `eq` ops and `a.length + b.length - 2*C(a,b)` non-`eq` ops.
* 3. CANONICAL , among the (often many) valid minimal scripts, return THE one
* defined below; the same `(a,b)` always yields it.
*
* The canonical script (the crux): read it left to right as an interleaving of
* `a` and `b`, walking cursors `(i, j)` from the start , `del` advances `i`,
* `ins` advances `j`, `eq` advances both (and requires `a[i] === b[j]`). Call an
* op *length-preserving at `(i, j)`* if, after taking it, the script can still be
* completed from the new position into a valid script meeting the clause-2
* minimality bound. At every step take the highest-priority length-preserving
* choice under this fixed priority:
* (1) `del` of `a[i]` if length-preserving at `(i, j)`;
* (2) else `ins` of `b[j]` if length-preserving at `(i, j)`;
* (3) else `eq` of the shared line (this case forces `a[i] === b[j]`).
*
* Implementation strategy:
* - Strip the common prefix and suffix (linear time/memory) so the expensive
* phase only sees the differing core.
* - Compute *a* minimal edit script for the core with Myers' O(ND)
* divide-and-conquer (linear memory , the V arrays are O(min(N,M))).
* - Re-assemble the full script (prefix eqs ++ core ++ suffix eqs) and
* `normalize` it to the unique canonical form by sliding every edit as far
* left as the priority order allows (see `normalize`). The canonical form is
* exactly the minimal script that contains none of the local patterns
* `eq L,del L` / `eq L,ins L` / `ins,del`, so removing those patterns yields
* it regardless of which minimal script the core solver produced.
*/
export function diff(a: string[], b: string[]): Edit[] {
const n = a.length;
const m = b.length;
// Common prefix / suffix (kept verbatim as eq ops). Correctness of the
// canonical form across these boundaries is restored by `normalize`.
let p = 0;
while (p < n && p < m && a[p] === b[p]) p++;
let s = 0;
while (s < n - p && s < m - p && a[n - 1 - s] === b[m - 1 - s]) s++;
const coreA = a.slice(p, n - s);
const coreB = b.slice(p, m - s);
const cn = coreA.length;
const cm = coreB.length;
const delA = new Uint8Array(cn);
const insB = new Uint8Array(cm);
if (cn > 0 && cm > 0) {
markCore(coreA, coreB, delA, insB);
} else if (cn > 0) {
delA.fill(1);
} else if (cm > 0) {
insB.fill(1);
}
const script: Edit[] = [];
for (let i = 0; i < p; i++) script.push({ op: "eq", line: a[i] as string });
{
let i = 0;
let j = 0;
while (i < cn || j < cm) {
if (i < cn && delA[i]) {
script.push({ op: "del", line: coreA[i] as string });
i++;
} else if (j < cm && insB[j]) {
script.push({ op: "ins", line: coreB[j] as string });
j++;
} else {
script.push({ op: "eq", line: coreA[i] as string });
i++;
j++;
}
}
}
for (let i = n - s; i < n; i++) script.push({ op: "eq", line: a[i] as string });
return normalize(script);
}
/**
* Mark which core-`a` lines are deleted and which core-`b` lines are inserted in
* a minimal edit script, using Myers' O(ND) linear-space divide-and-conquer.
* `delA[i]` / `insB[j]` are set for deleted / inserted lines; everything else is
* a match. The matches form a common subsequence aligned in order, so the caller
* can interleave them into a valid script.
*/
function markCore(A: string[], B: string[], delA: Uint8Array, insB: Uint8Array): void {
rec(0, A.length, 0, B.length);
// Subproblem is A[ai, ai+N) vs B[bi, bi+M). Marks are written at absolute
// core indices ai+.. / bi+..
function rec(ai: number, N: number, bi: number, M: number): void {
while (true) {
if (N === 0) {
for (let t = 0; t < M; t++) insB[bi + t] = 1;
return;
}
if (M === 0) {
for (let t = 0; t < N; t++) delA[ai + t] = 1;
return;
}
const snake = middleSnake(A, ai, N, B, bi, M);
const x = snake[0];
const y = snake[1];
const u = snake[2];
const v = snake[3];
const d = snake[4];
if (d > 1 || (x !== u && y !== v)) {
rec(ai, x, bi, y);
// tail-recurse on the second half to bound stack depth
ai = ai + u;
N = N - u;
bi = bi + v;
M = M - v;
continue;
}
// d <= 1 with an empty middle snake: a single indel against an otherwise
// identical pair. Whichever side is longer holds that one extra line.
if (M > N) {
for (let t = N; t < M; t++) insB[bi + t] = 1;
} else if (N > M) {
for (let t = M; t < N; t++) delA[ai + t] = 1;
}
return;
}
}
}
/**
* Find the middle snake of the optimal edit path between A[ai,ai+N) and
* B[bi,bi+M). Returns [x, y, u, v, D] where (x,y)->(u,v) is the matched diagonal
* run (the snake) and D is the total edit distance. Uses two O(min(N,M)) arrays.
*/
function middleSnake(
A: string[],
ai: number,
N: number,
B: string[],
bi: number,
M: number,
): [number, number, number, number, number] {
const w = N - M;
const Z = 2 * (N < M ? N : M) + 2;
const fwd = new Int32Array(Z);
const bwd = new Int32Array(Z);
const total = N + M;
const hmax = (total >> 1) + (total & 1);
const odd = (total & 1) === 1;
const mod = (k: number): number => ((k % Z) + Z) % Z;
for (let h = 0; h <= hmax; h++) {
// forward
{
const kStart = -(h - 2 * Math.max(0, h - M));
const kEnd = h - 2 * Math.max(0, h - N);
for (let k = kStart; k <= kEnd; k += 2) {
let a: number;
if (k === -h || (k !== h && fwd[mod(k - 1)] < fwd[mod(k + 1)])) {
a = fwd[mod(k + 1)] as number;
} else {
a = (fwd[mod(k - 1)] as number) + 1;
}
let b = a - k;
const s0 = a;
const t0 = b;
while (a < N && b < M && A[ai + a] === B[bi + b]) {
a++;
b++;
}
fwd[mod(k)] = a;
const z = w - k;
if (odd && z >= -(h - 1) && z <= h - 1 && a + (bwd[mod(z)] as number) >= N) {
return [s0, t0, a, b, 2 * h - 1];
}
}
}
// backward
{
const kStart = -(h - 2 * Math.max(0, h - M));
const kEnd = h - 2 * Math.max(0, h - N);
for (let k = kStart; k <= kEnd; k += 2) {
let a: number;
if (k === -h || (k !== h && bwd[mod(k - 1)] < bwd[mod(k + 1)])) {
a = bwd[mod(k + 1)] as number;
} else {
a = (bwd[mod(k - 1)] as number) + 1;
}
let b = a - k;
const s0 = a;
const t0 = b;
while (a < N && b < M && A[ai + N - 1 - a] === B[bi + M - 1 - b]) {
a++;
b++;
}
bwd[mod(k)] = a;
const z = w - k;
if (!odd && z >= -h && z <= h && a + (fwd[mod(z)] as number) >= N) {
return [N - a, M - b, N - s0, M - t0, 2 * h];
}
}
}
}
// Unreachable for valid inputs.
return [0, 0, N, M, total];
}
/**
* Slide every edit as far left as the canonical priority (`del` < `ins` < `eq`)
* allows, turning any minimal script into the unique canonical one. The three
* local rewrites , `eq L,del L`->`del L,eq L`, `eq L,ins L`->`ins L,eq L`, and
* `ins,del`->`del,ins` , are applied to exhaustion via an insertion-sort-style
* left bubble of each op as it is appended.
*/
function normalize(script: Edit[]): Edit[] {
const out: Edit[] = [];
for (const cur of script) {
out.push(cur);
let idx = out.length - 1;
while (idx > 0) {
const prev = out[idx - 1] as Edit;
const here = out[idx] as Edit;
if (shouldSwap(prev, here)) {
out[idx - 1] = here;
out[idx] = prev;
idx--;
} else {
break;
}
}
}
return out;
}
/** True when the adjacent pair (prev, cur) is a non-canonical pattern fixed by
* swapping them to (cur, prev). */
function shouldSwap(prev: Edit, cur: Edit): boolean {
// del before ins
if (prev.op === "ins" && cur.op === "del") return true;
// slide del left past an equal eq
if (prev.op === "eq" && cur.op === "del" && prev.line === cur.line) return true;
// slide ins left past an equal eq
if (prev.op === "eq" && cur.op === "ins" && prev.line === cur.line) return true;
return false;
}
The file /home/user/app/src/diff/myers.ts has been updated successfully. (file state is current in your context , no need to Read it back)
npx tsc -p tsconfig.json 2>&1 | head -30 && echo "BUILD DONE" && ls dist/src/diff/
BUILD DONE errors.js myers.js patch.js text.js types.js
import { diff } from "./dist/src/diff/myers.js";
import { applyPatch } from "./dist/src/diff/patch.js";
// ---- Oracle: canonical script per spec via suffix-LCS DP + priority greedy ----
function oracle(a, b) {
const n = a.length, m = b.length;
// L[i][j] = LCS(a[i..], b[j..])
const L = Array.from({ length: n + 1 }, () => new Int32Array(m + 1));
for (let i = n - 1; i >= 0; i--) {
for (let j = m - 1; j >= 0; j--) {
if (a[i] === b[j]) L[i][j] = L[i + 1][j + 1] + 1;
else L[i][j] = Math.max(L[i + 1][j], L[i][j + 1]);
}
}
const out = [];
let i = 0, j = 0;
while (i < n || j < m) {
if (i < n && j === m) { out.push({ op: "del", line: a[i] }); i++; continue; }
if (i === n && j < m) { out.push({ op: "ins", line: b[j] }); j++; continue; }
// both in range
// del LP iff L[i+1][j] === L[i][j]
if (L[i + 1][j] === L[i][j]) { out.push({ op: "del", line: a[i] }); i++; }
else if (L[i][j + 1] === L[i][j]) { out.push({ op: "ins", line: b[j] }); j++; }
else { out.push({ op: "eq", line: a[i] }); i++; j++; }
}
return out;
}
function eqScript(x, y) {
if (x.length !== y.length) return false;
for (let k = 0; k < x.length; k++) {
if (x[k].op !== y[k].op || x[k].line !== y[k].line) return false;
}
return true;
}
function rngArr(rng, maxLen, alpha) {
const len = Math.floor(rng() * (maxLen + 1));
const out = [];
for (let i = 0; i < len; i++) out.push(String.fromCharCode(97 + Math.floor(rng() * alpha)));
return out;
}
// simple seeded RNG
function mulberry32(seed) {
return function () {
seed |= 0; seed = (seed + 0x6D2B79F5) | 0;
let t = Math.imul(seed ^ (seed >>> 15), 1 | seed);
t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
};
}
let fails = 0;
let validFails = 0;
const rng = mulberry32(12345);
const N = 200000;
for (let it = 0; it < N; it++) {
const alpha = 1 + Math.floor(rng() * 4); // 1..4 symbols -> lots of repeats
const maxLen = Math.floor(rng() * 8);
const a = rngArr(rng, maxLen, alpha);
const b = rngArr(rng, maxLen, alpha);
let got;
try {
got = diff(a, b);
} catch (e) {
console.log("THREW", JSON.stringify(a), JSON.stringify(b), e.message);
fails++;
if (fails > 10) break;
continue;
}
// validity
let applied;
try { applied = applyPatch(a, got); } catch (e) {
console.log("INVALID(apply threw)", JSON.stringify(a), JSON.stringify(b), e.message);
validFails++; fails++;
if (fails > 10) break;
continue;
}
if (JSON.stringify(applied) !== JSON.stringify(b)) {
console.log("INVALID", JSON.stringify(a), "->", JSON.stringify(b), "got applied", JSON.stringify(applied));
validFails++; fails++;
if (fails > 10) break;
continue;
}
const want = oracle(a, b);
if (!eqScript(got, want)) {
console.log("MISMATCH a=", JSON.stringify(a), "b=", JSON.stringify(b));
console.log(" got ", JSON.stringify(got.map(e => e.op + ":" + e.line)));
console.log(" want", JSON.stringify(want.map(e => e.op + ":" + e.line)));
fails++;
if (fails > 20) break;
}
}
console.log("done", N, "cases, fails=", fails, "validFails=", validFails);
File created successfully at: /home/user/app/scratch_fuzz.mjs (file state is current in your context , no need to Read it back)
node scratch_fuzz.mjs 2>&1 | head -40
MISMATCH a= ["a","a","b"] b= ["b","a"] got ["del:a","ins:b","eq:a","del:b"] want ["del:a","del:a","eq:b","ins:a"] MISMATCH a= ["b","d","d","b","c"] b= ["d","a","d","b","d","b"] got ["ins:d","ins:a","ins:d","eq:b","del:d","eq:d","eq:b","del:c"] want ["del:b","ins:d","ins:a","eq:d","ins:b","eq:d","eq:b","del:c"] MISMATCH a= ["a","b","a","d"] b= ["a","d","b","c"] got ["eq:a","del:b","del:a","eq:d","ins:b","ins:c"] want ["del:a","del:b","eq:a","eq:d","ins:b","ins:c"] MISMATCH a= ["a","b","c","b"] b= ["c","d","c","c"] got ["del:a","del:b","eq:c","del:b","ins:d","ins:c","ins:c"] want ["del:a","del:b","ins:c","ins:d","ins:c","eq:c","del:b"] MISMATCH a= ["a","b","a","a","b"] b= ["a","b"] got ["eq:a","eq:b","del:a","del:a","del:b"] want ["del:a","del:b","del:a","eq:a","eq:b"] MISMATCH a= ["b","a","b","b"] b= ["b","a","b","a","b","b","b"] got ["eq:b","eq:a","eq:b","ins:a","ins:b","ins:b","eq:b"] want ["ins:b","ins:a","eq:b","eq:a","ins:b","eq:b","eq:b"] MISMATCH a= ["a","c","c","c","c","d"] b= ["d","b","c","b","b"] got ["del:a","del:c","del:c","del:c","ins:d","ins:b","eq:c","del:d","ins:b","ins:b"] want ["del:a","del:c","del:c","del:c","del:c","eq:d","ins:b","ins:c","ins:b","ins:b"] MISMATCH a= ["b","a","b","a","a"] b= ["a","b","b","b","b","b","a"] got ["del:b","eq:a","eq:b","del:a","ins:b","ins:b","ins:b","ins:b","eq:a"] want ["del:b","eq:a","ins:b","ins:b","ins:b","ins:b","eq:b","del:a","eq:a"] MISMATCH a= ["a","b"] b= ["b","a","a"] got ["ins:b","eq:a","del:b","ins:a"] want ["del:a","eq:b","ins:a","ins:a"] MISMATCH a= ["b","a"] b= ["b","c","b"] got ["eq:b","del:a","ins:c","ins:b"] want ["ins:b","ins:c","eq:b","del:a"] MISMATCH a= ["a","b","a","b"] b= ["a","b","b","a"] got ["eq:a","eq:b","del:a","eq:b","ins:a"] want ["eq:a","ins:b","eq:b","eq:a","del:b"] MISMATCH a= ["a","c"] b= ["a","a"] got ["eq:a","del:c","ins:a"] want ["ins:a","eq:a","del:c"] MISMATCH a= ["c","b","a","b"] b= ["c","a","a"] got ["eq:c","del:b","eq:a","del:b","ins:a"] want ["eq:c","del:b","ins:a","eq:a","del:b"] MISMATCH a= ["b","c","b","a","c","c","b"] b= ["c","d","a","a"]
import type { Edit } from "./types.js";
/**
* Compute the canonical minimal line-level edit script transforming `a` into `b`.
*
* Return an ordered `Edit[]` that, replayed against `a` by `applyPatch`,
* reproduces `b`. An `eq` consumes one line from each side (the lines are
* equal); a `del` consumes one line from `a`; an `ins` consumes one line from
* `b`. (See `EditOp` in types.ts.) The script must satisfy ALL THREE of the
* following; each is checked independently and validity + minimality is NOT
* sufficient.
*
* 1. VALID , `applyPatch(a, diff(a, b))` deep-equals `b`.
* 2. MINIMAL , fewest non-`eq` ops of any valid script (LCS-optimal).
* 3. CANONICAL , among the many valid minimal scripts, return THE one whose
* left-to-right walk always takes the highest-priority length-preserving op
* under the order `del` > `ins` > `eq` (see the task spec).
*
* Strategy:
* - Strip the common prefix and suffix (linear time/memory) so the expensive
* phase only sees the differing core.
* - Solve the core with a canonical-aware Hirschberg (linear-memory LCS
* divide-and-conquer): at every split the left/topmost choice consistent
* with "delete early / match late" is taken, reproducing the priority order.
* - Re-assemble (prefix eqs ++ core ++ suffix eqs) and `normalize`, which
* slides edits left past equal context and orders `del` before `ins`. This
* repairs the only discrepancy stripping can introduce: a prefix line that
* the global canonical would delete rather than match (always an
* equal-line slide).
*/
export function diff(a: string[], b: string[]): Edit[] {
const n = a.length;
const m = b.length;
let p = 0;
while (p < n && p < m && a[p] === b[p]) p++;
let s = 0;
while (s < n - p && s < m - p && a[n - 1 - s] === b[m - 1 - s]) s++;
const coreA = a.slice(p, n - s);
const coreB = b.slice(p, m - s);
const script: Edit[] = [];
for (let i = 0; i < p; i++) script.push({ op: "eq", line: a[i] as string });
diffCore(coreA, coreB, script);
for (let i = n - s; i < n; i++) script.push({ op: "eq", line: a[i] as string });
return normalize(script);
}
/**
* Emit a canonical minimal edit script for A vs B into `out`, using a
* Hirschberg-style linear-memory LCS divide-and-conquer. Only two O(min)-ish
* length arrays are alive at any depth, so memory stays proportional to input.
*/
function diffCore(A: string[], B: string[], out: Edit[]): void {
hir(0, A.length, 0, B.length);
function hir(ai: number, N: number, bi: number, M: number): void {
// Trim local common prefix/suffix to shrink the LCS work per call.
while (N > 0 && M > 0 && A[ai] === B[bi]) {
out.push({ op: "eq", line: A[ai] as string });
ai++;
bi++;
N--;
M--;
}
// We cannot eagerly emit a common suffix here (it would be emitted before
// the middle ops), so only prefix-trim inside the recursion.
if (N === 0) {
for (let t = 0; t < M; t++) out.push({ op: "ins", line: B[bi + t] as string });
return;
}
if (M === 0) {
for (let t = 0; t < N; t++) out.push({ op: "del", line: A[ai + t] as string });
return;
}
if (M === 1) {
const x = B[bi] as string;
let last = -1;
for (let t = 0; t < N; t++) if (A[ai + t] === x) last = t;
if (last < 0) {
for (let t = 0; t < N; t++) out.push({ op: "del", line: A[ai + t] as string });
out.push({ op: "ins", line: x });
} else {
for (let t = 0; t < last; t++) out.push({ op: "del", line: A[ai + t] as string });
out.push({ op: "eq", line: x });
for (let t = last + 1; t < N; t++) out.push({ op: "del", line: A[ai + t] as string });
}
return;
}
const mid = M >> 1;
const f = lcsForward(A, ai, N, B, bi, mid);
const g = lcsBackward(A, ai, N, B, bi + mid, M - mid);
// Choose the split index k (a-cut) maximizing f[k]+g[k]. Among ties pick the
// largest k: more a-lines fall into the left (earlier) half, matching the
// "delete early / match late" priority.
let best = -1;
let bestK = 0;
for (let k = N; k >= 0; k--) {
const total = (f[k] as number) + (g[k] as number);
if (total > best) {
best = total;
bestK = k;
}
}
hir(ai, bestK, bi, mid);
hir(ai + bestK, N - bestK, bi + mid, M - mid);
}
}
/** f[i] = LCS(A[ai, ai+i), B[bi, bi+width)) for i in 0..N. O(width) memory. */
function lcsForward(
A: string[],
ai: number,
N: number,
B: string[],
bi: number,
width: number,
): Int32Array {
const f = new Int32Array(N + 1);
const row = new Int32Array(width + 1);
for (let i = 1; i <= N; i++) {
let prev = 0; // row[0] of the previous a-line (always 0)
const ax = A[ai + i - 1];
for (let c = 1; c <= width; c++) {
const tmp = row[c] as number;
if (ax === B[bi + c - 1]) row[c] = prev + 1;
else if ((row[c] as number) < (row[c - 1] as number)) row[c] = row[c - 1] as number;
prev = tmp;
}
f[i] = row[width] as number;
}
return f;
}
/** g[i] = LCS(A[ai+i, ai+N), B[bi, bi+width)) for i in 0..N. O(width) memory. */
function lcsBackward(
A: string[],
ai: number,
N: number,
B: string[],
bi: number,
width: number,
): Int32Array {
const g = new Int32Array(N + 1);
const row = new Int32Array(width + 1);
for (let i = N - 1; i >= 0; i--) {
let diag = row[width] as number; // LCS(A[ai+i+1..], B[..end]) = 0
const ax = A[ai + i];
for (let q = width - 1; q >= 0; q--) {
const tmp = row[q] as number;
if (ax === B[bi + q]) row[q] = diag + 1;
else if ((row[q] as number) < (row[q + 1] as number)) row[q] = row[q + 1] as number;
diag = tmp;
}
g[i] = row[0] as number;
}
return g;
}
/**
* Slide every edit as far left as the canonical priority (`del` < `ins` < `eq`)
* allows. Repairs the prefix/suffix-strip boundary by applying, to exhaustion,
* the rewrites `eq L,del L`->`del L,eq L`, `eq L,ins L`->`ins L,eq L`, and
* `ins,del`->`del,ins` via an insertion-sort-style left bubble.
*/
function normalize(script: Edit[]): Edit[] {
const out: Edit[] = [];
for (const cur of script) {
out.push(cur);
let idx = out.length - 1;
while (idx > 0 && shouldSwap(out[idx - 1] as Edit, out[idx] as Edit)) {
const prev = out[idx - 1] as Edit;
out[idx - 1] = out[idx] as Edit;
out[idx] = prev;
idx--;
}
}
return out;
}
function shouldSwap(prev: Edit, cur: Edit): boolean {
if (prev.op === "ins" && cur.op === "del") return true;
if (prev.op === "eq" && cur.op === "del" && prev.line === cur.line) return true;
if (prev.op === "eq" && cur.op === "ins" && prev.line === cur.line) return true;
return false;
}
The file /home/user/app/src/diff/myers.ts has been updated successfully. (file state is current in your context , no need to Read it back)
npx tsc -p tsconfig.json 2>&1 | head -20 && echo BUILD_OK && node scratch_fuzz.mjs 2>&1 | head -40
BUILD_OK MISMATCH a= ["b","d","d","b","c"] b= ["d","a","d","b","d","b"] got ["del:b","eq:d","ins:a","eq:d","eq:b","del:c","ins:d","ins:b"] want ["del:b","ins:d","ins:a","eq:d","ins:b","eq:d","eq:b","del:c"] MISMATCH a= ["b"] b= ["a","b","c","b","a"] got ["ins:a","eq:b","ins:c","ins:b","ins:a"] want ["ins:a","ins:b","ins:c","eq:b","ins:a"] MISMATCH a= ["a","b","a","d"] b= ["a","d","b","c"] got ["eq:a","del:b","del:a","eq:d","ins:b","ins:c"] want ["del:a","del:b","eq:a","eq:d","ins:b","ins:c"] MISMATCH a= ["a","b","c","b"] b= ["c","d","c","c"] got ["del:a","del:b","eq:c","del:b","ins:d","ins:c","ins:c"] want ["del:a","del:b","ins:c","ins:d","ins:c","eq:c","del:b"] MISMATCH a= ["a","b","a","a","b"] b= ["a","b"] got ["eq:a","eq:b","del:a","del:a","del:b"] want ["del:a","del:b","del:a","eq:a","eq:b"] MISMATCH a= ["b","a","b","b"] b= ["b","a","b","a","b","b","b"] got ["eq:b","eq:a","eq:b","ins:a","ins:b","ins:b","eq:b"] want ["ins:b","ins:a","eq:b","eq:a","ins:b","eq:b","eq:b"] MISMATCH a= ["b","a","b","a","a"] b= ["a","b","b","b","b","b","a"] got ["del:b","eq:a","eq:b","del:a","ins:b","ins:b","ins:b","ins:b","eq:a"] want ["del:b","eq:a","ins:b","ins:b","ins:b","ins:b","eq:b","del:a","eq:a"] MISMATCH a= ["b","a"] b= ["b","c","b"] got ["eq:b","del:a","ins:c","ins:b"] want ["ins:b","ins:c","eq:b","del:a"] MISMATCH a= ["a","b","a","b"] b= ["a","b","b","a"] got ["eq:a","eq:b","del:a","eq:b","ins:a"] want ["eq:a","ins:b","eq:b","eq:a","del:b"] MISMATCH a= ["a","c"] b= ["a","a"] got ["eq:a","del:c","ins:a"] want ["ins:a","eq:a","del:c"] MISMATCH a= ["c","b","a","b"] b= ["c","a","a"] got ["eq:c","del:b","eq:a","del:b","ins:a"] want ["eq:c","del:b","ins:a","eq:a","del:b"] MISMATCH a= ["b","c","b","a","c","c","b"] b= ["c","d","a","a"] got ["del:b","eq:c","del:b","ins:d","eq:a","del:c","del:c","del:b","ins:a"] want ["del:b","eq:c","del:b","ins:d","ins:a","eq:a","del:c","del:c","del:b"] MISMATCH a= ["b","a","b","b"] b= ["b","b","a"] got ["eq:b","del:a","del:b","eq:b","ins:a"] want ["del:b","del:a","eq:b","eq:b","ins:a"] MISMATCH a= ["a","b","b","b","b"] b= ["a","a"]
/home/user/app/src/diff/myers.ts
function hir(ai: number, N: number, bi: number, M: number): void {
// Trim local common prefix/suffix to shrink the LCS work per call.
while (N > 0 && M > 0 && A[ai] === B[bi]) {
out.push({ op: "eq", line: A[ai] as string });
ai++;
bi++;
N--;
M--;
}
// We cannot eagerly emit a common suffix here (it would be emitted before
// the middle ops), so only prefix-trim inside the recursion.
if (N === 0) { function hir(ai: number, N: number, bi: number, M: number): void {
if (N === 0) {The file /home/user/app/src/diff/myers.ts has been updated successfully. (file state is current in your context , no need to Read it back)
npx tsc -p tsconfig.json 2>&1 | head -20 && echo BUILD_OK && node scratch_fuzz.mjs 2>&1 | head -30
BUILD_OK MISMATCH a= ["b","d","d","b","c"] b= ["d","a","d","b","d","b"] got ["del:b","eq:d","ins:a","eq:d","eq:b","del:c","ins:d","ins:b"] want ["del:b","ins:d","ins:a","eq:d","ins:b","eq:d","eq:b","del:c"] MISMATCH a= ["b"] b= ["a","b","c","b","a"] got ["ins:a","eq:b","ins:c","ins:b","ins:a"] want ["ins:a","ins:b","ins:c","eq:b","ins:a"] MISMATCH a= ["a","b","a","d"] b= ["a","d","b","c"] got ["eq:a","del:b","del:a","eq:d","ins:b","ins:c"] want ["del:a","del:b","eq:a","eq:d","ins:b","ins:c"] MISMATCH a= ["a","b","c","b"] b= ["c","d","c","c"] got ["del:a","del:b","eq:c","del:b","ins:d","ins:c","ins:c"] want ["del:a","del:b","ins:c","ins:d","ins:c","eq:c","del:b"] MISMATCH a= ["a","b","a","a","b"] b= ["a","b"] got ["eq:a","eq:b","del:a","del:a","del:b"] want ["del:a","del:b","del:a","eq:a","eq:b"] MISMATCH a= ["b","a","b","b"] b= ["b","a","b","a","b","b","b"] got ["eq:b","eq:a","eq:b","ins:a","ins:b","ins:b","eq:b"] want ["ins:b","ins:a","eq:b","eq:a","ins:b","eq:b","eq:b"] MISMATCH a= ["b","a","b","a","a"] b= ["a","b","b","b","b","b","a"] got ["del:b","eq:a","eq:b","del:a","ins:b","ins:b","ins:b","ins:b","eq:a"] want ["del:b","eq:a","ins:b","ins:b","ins:b","ins:b","eq:b","del:a","eq:a"] MISMATCH a= ["b","a"] b= ["b","c","b"] got ["eq:b","del:a","ins:c","ins:b"] want ["ins:b","ins:c","eq:b","del:a"] MISMATCH a= ["a","b","a","b"] b= ["a","b","b","a"] got ["eq:a","eq:b","del:a","eq:b","ins:a"] want ["eq:a","ins:b","eq:b","eq:a","del:b"] MISMATCH a= ["a","c"] b= ["a","a"] got ["eq:a","del:c","ins:a"] want ["ins:a","eq:a","del:c"]
No file changes, the agent left the workspace untouched.
=== running test suite in /home/user/app ===
RUN v1.6.0 /home/user/app
✓ test/diff.test.ts > diff > canonical edit scripts (pinned by the del-before-ins tie-break) > replace in the middle
✓ test/diff.test.ts > diff > canonical edit scripts (pinned by the del-before-ins tie-break) > a transposition keeps the LATER match and deletes the earlier line
✓ test/diff.test.ts > diff > canonical edit scripts (pinned by the del-before-ins tie-break) > duplicate runs align to the LAST surviving equal lines
✓ test/diff.test.ts > diff > canonical edit scripts (pinned by the del-before-ins tie-break) > interleaved unique deletions collapse to eq/del pairs
✓ test/diff.test.ts > diff > canonical edit scripts (pinned by the del-before-ins tie-break) > classic ABCABBA / CBABAC example resolves to the canonical script
✓ test/diff.test.ts > diff > round-trips through applyPatch on realistic text > patches a small source edit
✓ test/diff.test.ts > diff > round-trips through applyPatch on realistic text > preserves a trailing newline through split/diff/apply/join
× test/diff.test.ts > diff > canonical script , exhaustive over small inputs > matches the independent canonical oracle for every 2-letter pair up to length 5
→ expected [ { op: 'eq', line: 'a' }, …(2) ] to deeply equal [ { op: 'ins', line: 'a' }, …(2) ]
× test/diff.test.ts > diff > canonical script , exhaustive over small inputs > matches the independent canonical oracle for every 3-letter pair up to length 4
→ expected [ { op: 'eq', line: 'a' }, …(2) ] to deeply equal [ { op: 'ins', line: 'a' }, …(2) ]
× test/diff.test.ts > diff > adversarial: randomized exact-canonical differential > matches the canonical oracle across many longer, duplicate-heavy pairs
→ expected [ { op: 'del', line: 'd' }, …(12) ] to deeply equal [ { op: 'del', line: 'd' }, …(12) ]
× test/diff.test.ts > diff > adversarial: randomized exact-canonical differential > matches the canonical oracle on a binary alphabet (maximal ambiguity)
→ expected [ { op: 'eq', line: '0' }, …(15) ] to deeply equal [ { op: 'eq', line: '0' }, …(15) ]
✓ test/diff.test.ts > diff > adversarial: randomized exact-canonical differential > scales to a larger near-identical pair (single-line change)
✓ test/diff.test.ts > diff > performance: must stay within O(n*m) and produce the canonical script > diffs a 1500x1500 low-overlap pair well under the timeout
✓ test/diff.test.ts > diff > performance: must stay within O(n*m) and produce the canonical script > produces the canonical script on a 2000x2000 block-edit pair
✓ test/diff.test.ts > diff > tie-break orientation , extra hand-pinned litmus cases > reverse transposition still keeps the LATER match (del earlier copy first)
✓ test/diff.test.ts > diff > tie-break orientation , extra hand-pinned litmus cases > 3-cycle rotation resolves to the canonical del-before-ins script
× test/diff.test.ts > diff > tie-break orientation , extra hand-pinned litmus cases > a duplicated line that is removed keeps the LAST surviving copy
→ expected [ { op: 'eq', line: 'a' }, …(2) ] to deeply equal [ { op: 'del', line: 'a' }, …(2) ]
× test/diff.test.ts > diff > tie-break orientation , extra hand-pinned litmus cases > growing a run of duplicates inserts at the canonical position
→ expected [ { op: 'eq', line: 'a' }, …(2) ] to deeply equal [ { op: 'ins', line: 'a' }, …(2) ]
✓ test/diff.test.ts > diff > tie-break orientation , extra hand-pinned litmus cases > symmetry is NOT assumed: diff(a,b) and diff(b,a) are independently canonical
✓ test/diff.test.ts > diff > adversarial edge cases > no common subsequence at all -> all del then all ins, in that order
✓ test/diff.test.ts > diff > adversarial edge cases > single-element equal / unequal
✓ test/diff.test.ts > diff > adversarial edge cases > very long common prefix with a single trailing change
✓ test/diff.test.ts > diff > adversarial edge cases > very long common suffix with a single leading change
✓ test/diff.test.ts > diff > adversarial edge cases > an all-identical block shrinks by deleting the surplus from the LEFT
✓ test/diff.test.ts > diff > adversarial edge cases > unicode, emoji, and whitespace-only lines compare by exact string equality
✓ test/diff.test.ts > diff > adversarial edge cases > lines that look like edit ops or contain newlines are treated opaquely
✓ test/diff.test.ts > diff > adversarial edge cases > combining-character vs precomposed forms are NOT equal (no normalization)
× test/diff.test.ts > diff > canonical script , WIDER exhaustive sweeps (cross-checked oracles) > matches both canonical oracles for every 2-letter pair up to length 6
→ expected [ { op: 'eq', line: 'a' }, …(2) ] to deeply equal [ { op: 'ins', line: 'a' }, …(2) ]
× test/diff.test.ts > diff > canonical script , WIDER exhaustive sweeps (cross-checked oracles) > matches both canonical oracles for every 3-letter pair up to length 5
→ expected [ { op: 'eq', line: 'a' }, …(2) ] to deeply equal [ { op: 'ins', line: 'a' }, …(2) ]
× test/diff.test.ts > diff > adversarial: LARGER randomized exact-canonical differential > matches both oracles across thousands of long, duplicate-heavy pairs
→ expected [ { op: 'del', line: 'a' }, …(18) ] to deeply equal [ { op: 'del', line: 'a' }, …(18) ]
× test/diff.test.ts > diff > adversarial: LARGER randomized exact-canonical differential > stays canonical with realistic line strings and block moves
→ expected [ …(55) ] to deeply equal [ …(55) ]
✓ test/diff.test.ts > diff > performance: an inefficient or super-quadratic approach times out > diffs a 2200x2200 low-overlap pair within a tight timeout
✓ test/diff.test.ts > diff > performance: an inefficient or super-quadratic approach times out > diffs a 3000x3000 block-edit pair within a tight timeout 375ms
× test/diff.test.ts > diff > canonical script , WIDEST exhaustive sweep (binary, length <= 7) > matches both canonical oracles for every 2-letter pair up to length 7
→ expected [ { op: 'eq', line: 'a' }, …(2) ] to deeply equal [ { op: 'ins', line: 'a' }, …(2) ]
✓ test/diff.test.ts > diff > deep tie-break chains , del-before-ins must hold across long runs > all-distinct replacement block: every del precedes every ins
✓ test/diff.test.ts > diff > deep tie-break chains , del-before-ins must hold across long runs > alternating shared/unique forces del-before-ins at each junction
✓ test/diff.test.ts > diff > deep tie-break chains , del-before-ins must hold across long runs > deletion defers to insertion exactly when deleting would break minimality
✓ test/diff.test.ts > diff > latest-anchor under heavy duplication , the later copy survives > shrinking a duplicate run deletes the LEFT surplus
✓ test/diff.test.ts > diff > latest-anchor under heavy duplication , the later copy survives > growing a duplicate run inserts BEFORE the surviving (later) anchor
✓ test/diff.test.ts > diff > latest-anchor under heavy duplication , the later copy survives > interleaved duplicates keep each latest viable anchor
✓ test/diff.test.ts > diff > latest-anchor under heavy duplication , the later copy survives > two distinct repeated lines interleaved keep their own latest anchors
× test/diff.test.ts > diff > adversarial: SECOND larger randomized exact-canonical differential > matches both oracles across many short-alphabet, duplicate-saturated pairs
→ expected [ { op: 'del', line: 'b' }, …(15) ] to deeply equal [ { op: 'del', line: 'b' }, …(15) ]
✓ test/diff.test.ts > diff > memory: large mostly-identical inputs must not build an n*m table > change at the START (long common suffix)
✓ test/diff.test.ts > diff > memory: large mostly-identical inputs must not build an n*m table > change at the END (long common prefix)
✓ test/diff.test.ts > diff > memory: large mostly-identical inputs must not build an n*m table > change in the MIDDLE (long common prefix AND suffix)
✓ test/diff.test.ts > diff > memory: large mostly-identical inputs must not build an n*m table > identical huge inputs -> all eq
✓ test/diff.test.ts > diff > more edge cases (added) > op-name strings ('eq'/'del'/'ins') as line content are opaque
× test/diff.test.ts > diff > more edge cases (added) > empty-string lines interspersed
→ expected [ { op: 'del', line: '' }, …(5) ] to deeply equal [ { op: 'del', line: '' }, …(5) ]
✓ test/diff.test.ts > diff > more edge cases (added) > whitespace-only lines that differ by kind
× test/diff.test.ts > diff > more edge cases (added) > lines containing embedded newlines are single opaque values
→ expected [ { op: 'eq', line: 'a\nb' }, …(3) ] to deeply equal [ { op: 'ins', line: 'a\nb' }, …(3) ]
✓ test/diff.test.ts > diff > more edge cases (added) > unicode: combining vs precomposed are distinct (no normalization)
✓ test/diff.test.ts > diff > more edge cases (added) > emoji ZWJ sequences are opaque strings
✓ test/diff.test.ts > diff > more edge cases (added) > b is the reverse of a
✓ test/diff.test.ts > diff > more edge cases (added) > difference is only trailing whitespace
✓ test/diff.test.ts > diff > more edge cases (added) > repeated block pattern, cyclically shifted
✓ test/diff.test.ts > diff > more edge cases (added) > long run of one value with a single mid insertion (latest anchor)
✓ test/diff.test.ts > diff > more edge cases (added) > JSON-looking duplicate lines align by latest anchor
✓ test/diff.test.ts > diff > more edge cases (added) > medium near-identical: one line changed among 60
✓ test/diff.test.ts > diff > large un-peelable cores: sub-quadratic memory AND exact canonical > disjoint halves bridged by a shared duplicate comb 2772ms
✓ test/diff.test.ts > diff > large un-peelable cores: sub-quadratic memory AND exact canonical > alternating (p,q) vs (q,p) at scale 3208ms
✓ test/diff.test.ts > diff > large un-peelable cores: sub-quadratic memory AND exact canonical > peelable unique affixes around a large duplicate mid-core
✓ test/diff.test.ts > diff > more hardening edge cases (added) > highly skewed sizes: one line vs a large block, single match
✓ test/diff.test.ts > diff > more hardening edge cases (added) > trailing newline (final empty entry) is matched as eq at scale
✓ test/diff.test.ts > diff > more hardening edge cases (added) > deep alternating shared/unique tie-break chain at scale
✓ test/diff.test.ts > diff > large ambiguous duplicate-heavy cores match the canonical script > linear-space oracle agrees with the n*m oracle on every 2-letter pair up to length 6 354ms
× test/diff.test.ts > diff > large ambiguous duplicate-heavy cores match the canonical script > diff matches the linear-space canonical oracle on large random small-alphabet pairs 15823ms
→ expected [ { op: 'ins', line: '1' }, …(20949) ] to deeply equal [ { op: 'ins', line: '1' }, …(20949) ]
✓ test/patch.test.ts > applyPatch (provided) > replays eq/del/ins to reconstruct the target
✓ test/patch.test.ts > applyPatch (provided) > throws trailing_lines when the script leaves original lines unconsumed
⎯⎯⎯⎯⎯⎯ Failed Tests 15 ⎯⎯⎯⎯⎯⎯⎯
FAIL test/diff.test.ts > diff > canonical script , exhaustive over small inputs > matches the independent canonical oracle for every 2-letter pair up to length 5
AssertionError: expected [ { op: 'eq', line: 'a' }, …(2) ] to deeply equal [ { op: 'ins', line: 'a' }, …(2) ]
- Expected
+ Received
Array [
Object {
"line": "a",
- "op": "ins",
+ "op": "eq",
},
Object {
"line": "b",
"op": "ins",
},
Object {
"line": "a",
- "op": "eq",
+ "op": "ins",
},
]
❯ test/diff.test.ts:406:25
404| const edits = diff(a, b);
405| expectValidMinimal(a, b, edits);
406| expect(edits).toEqual(canonicalScript(a, b));
| ^
407| checked++;
408| }
⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[1/15]⎯
FAIL test/diff.test.ts > diff > canonical script , exhaustive over small inputs > matches the independent canonical oracle for every 3-letter pa
… (truncated at 12,000 chars, full verifier log is in the trial artifacts)Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_5c61f9ac0ffd499d. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.
Trial trial_5c61f9ac0ffd499d · verifier authoritative; classifier explanatory.