node:util: implement diff edit tuple helper

[andrewtdiz]

Summary

Perry does not implement util.diff(actual, expected). Node exposes this helper and returns an edit-tuple sequence for string inputs and arrays of strings, with validation errors for unsupported input types.

Node Behavior

Minimal repro:

import * as util from "node:util";

console.log("diff typeof:", typeof util.diff);

for (const [actual, expected] of [
  ["abc", "adc"],
  [["a", "b", "c"], ["a", "d", "c"]],
  ["same", "same"],
  [123, "x"],
  ["x", 123],
] as any[]) {
  try {
    console.log(`${JSON.stringify(actual)} -> ${JSON.stringify(expected)}:`, JSON.stringify(util.diff(actual, expected)));
  } catch (err) {
    const e = err as NodeJS.ErrnoException;
    console.log(`${JSON.stringify(actual)} -> ${JSON.stringify(expected)} error:`, e.name, e.code, e.message.split("\n")[0]);
  }
}

Node v25.9.0 with FORCE_COLOR=0 node --experimental-strip-types prints:

diff typeof: function
"abc" -> "adc": [[0,"a"],[1,"b"],[-1,"d"],[0,"c"]]
["a","b","c"] -> ["a","d","c"]: [[0,"a"],[1,"b"],[-1,"d"],[0,"c"]]
"same" -> "same": []
123 -> "x" error: TypeError ERR_INVALID_ARG_TYPE The "actual" argument must be of type string. Received type number (123)
"x" -> 123 error: TypeError ERR_INVALID_ARG_TYPE The "expected" argument must be of type string. Received type number (123)

Perry Behavior

Focused probe test-files/tmp_util_diff.ts fails at compile time:

Collecting modules...
Error: `util.diff` is not implemented in Perry — see `perry --print-api-manifest` for the supported surface, or set `PERRY_ALLOW_UNIMPLEMENTED=1` to ignore. (#463)

Evidence:

• ./run_parity_tests.sh --filter tmp_util_diff
• report: test-parity/reports/parity_report_20260530_110312.json
• Node output: test-parity/output/node/tmp_util_diff.txt
• Perry compile log: test-parity/output/tmp_util_diff.compile_error.log
• docs list util.diff(actual, expected) as a gap in docs/runtime-parity-gaps.md.
• crates/perry-api-manifest/src/entries.rs omits diff from the supported util surface.

Suggested PR Cut

Batch this with related issues in:
node:util: comparison helper parity

Good batch candidates:

• node:util: implement remaining top-level helper APIs #2514

Do not batch with:

• unrelated modules
• broad subsystem rewrites
• fixes needing different test harnesses

Acceptance

• parity/regression test proves string and string-array diffs return Node-compatible edit tuples
• invalid input types throw Node-compatible ERR_INVALID_ARG_TYPE errors
• related known-failure/docs/manifest entries updated if touched

[andrewtdiz]

I’m taking this as a focused node:util diff helper PR cut. Intended scope: implement util.diff for strings and arrays of strings with Node-shaped edit tuples and validation, plus focused parity coverage and manifest/docs updates. Non-goals: broader comparison helper work or unrelated util APIs.

[andrewtdiz]

Implemented in #3462.

Summary:

• Added util.diff(actual, expected) for strings, arrays of strings, and mixed string/string-array inputs.
• Returns Node-shaped edit tuples with LCS ordering, including identical string [] behavior and common tuples for identical string arrays.
• Added ERR_INVALID_ARG_TYPE validation for unsupported inputs and non-string array elements.
• Wired util/sys manifest entries, native namespace enumeration, native dispatch, codegen declarations, docs, and focused parity coverage.

Validation:

• Focused node-suite/util/diff/basic parity passes.
• Full util parity is 72/73; the remaining failure is the existing node-suite/util/get-system-error mismatch.
• cargo check, cargo fmt --all -- --check, git diff --check, jq empty test-parity/known_failures.json, and ./scripts/check_file_size.sh pass.