Claude Haiku 5.5 (effort default (no --effort flag) · thinking on) on Make a Node.js JSON Patch module correct (no input mutation, pointer escaping, array index rules, move-into-child, deep test, error codes)

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  "result": "I rewrote `patch.js` to follow `PATCH_SPEC.md`, and all 22 tests I added in `test/patch.test.js` pass under `node --test test/` on Node 20.19.2. I haven't run it against the hidden suite.\n\nWhat changed:\n- **No mutation:** `apply` deep-clones `doc` once and works on the copy. Values added by `add`, `replace`, `copy`, and `move` are cloned or moved from that copy. A failure throws before anything is returned, so the caller's inputs are never touched.\n- **Pointers:** `\"\"` is the whole document. Anything else must start with `/` (`BAD_POINTER`). Tokens decode `~1` then `~0`.\n- **Objects:** only own properties count, so `constructor` or `toString` are missing members. Writes use `defineProperty`, so `__proto__` is an ordinary key.\n- **Arrays:** index tokens must be `0` or a number with no leading zeros (`BAD_INDEX`). `-` is valid only as the final `add`/`move`/`copy` target. `add` may insert at the length; other uses need an index below the length (`PATH_NOT_FOUND`).\n- **Operations:** `move` checks `from` exists, then rejects a proper descendant target (`MOVE_INTO_CHILD`), then removes and adds. Equal paths are a no-op. `test` uses the spec's deep equality.\n- **Errors:** every failure is a `PatchError` with `code` and `index` (the failing op's position). Malformed ops give `BAD_OP`, and the first failing op decides the error.\n\nDecisions the spec didn't cover:\n- `remove` with path `\"\"` throws `BAD_OP`, since removing the whole document has no JSON result.\n- If `ops` is not an array, `apply` throws `BAD_OP` with `index` set to `undefined`.\n- `PatchError` now takes `(code, message)` instead of `(message)`. Only `apply` builds these in the module itself, so this only matters if a caller constructs one directly.\n\nThe work directory is not a git repository, so I did not commit anything.",
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