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Add helper to update JSON files safely #2

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61 changes: 61 additions & 0 deletions update_json.py
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Original file line number Diff line number Diff line change
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"""Utilities for updating JSON files."""
from __future__ import annotations

import json
import os
from collections.abc import Mapping
from typing import Any


def update_json_file(path: str, new_data: Mapping[str, Any]) -> bool:
"""Update JSON keys in ``path`` with values from ``new_data``.

The function reads the current JSON content from ``path``. If the file does not
exist, it is created with ``new_data`` as its content. When the file exists, only
keys already present in the JSON document are updated. Other keys in
``new_data`` are ignored so the structure of the original document is
preserved.

Args:
path: Path to the JSON file that should be updated.
new_data: Mapping containing key/value pairs to update.

Returns:
``True`` if the update succeeds, otherwise ``False``.
"""

if not isinstance(new_data, Mapping):
return False

try:
existing_data: dict[str, Any] = {}
file_exists = os.path.exists(path)

if file_exists:
with open(path, "r", encoding="utf-8") as file:
content = file.read().strip()

if content:
loaded = json.loads(content)
if not isinstance(loaded, dict):
return False
existing_data = loaded
else:
directory = os.path.dirname(path)
if directory:
os.makedirs(directory, exist_ok=True)

if file_exists:
for key, value in new_data.items():
if key in existing_data:
existing_data[key] = value
Comment on lines +48 to +51
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@chatgpt-codex-connector chatgpt-codex-connector bot Oct 2, 2025

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P1 Badge Overwrite nested JSON objects instead of merging

When the target file exists, the loop replaces an entire value whenever the top-level key is present. If that value is itself a dictionary, providing a partial update will clobber unspecified nested keys. For example, an existing document { "settings": { "theme": "dark", "lang": "en" } } updated with new_data={"settings": {"lang": "fr"}} results in {"settings": {"lang": "fr"}}, losing theme. This contradicts the docstring’s promise to preserve the original structure and can silently drop data. A recursive merge is needed to update only the provided nested keys.

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else:
existing_data = dict(new_data)

with open(path, "w", encoding="utf-8") as file:
json.dump(existing_data, file, ensure_ascii=False, indent=4)
file.write("\n")

return True
except (OSError, json.JSONDecodeError):
return False