JSON::Repair 
This is a Ruby gem designed to repair broken JSON strings. Inspired by and based on the jsonrepair js library. It efficiently handles and corrects malformed JSON data, making it especially useful in scenarios where JSON output from LLMs might not strictly adhere to JSON standards. Whether it's missing quotes, misplaced commas, or unexpected characters, it ensures that the JSON data is valid and can be parsed correctly.
Installation
Add this gem to your application's Gemfield by executing:
$ bundle add json-repair
Alternatively, if you are not using Bundler to manage your dependencies:
$ gem install json-repair
Usage
Using JSON::Repair is straightforward. Simply call the repair method with a JSON string as an argument:
require 'json/repair'
# Example of repairing a JSON string
broken_json = '{name: Alice, "age": 25,}'
repaired_json = JSON.repair(broken_json)
puts repaired_json # Outputs: {"name":"Alice","age":25}
The repair method takes a string containing JSON data and returns a corrected version of this string, ensuring it is valid JSON.
Pass return_objects: true to get the parsed Ruby value (Hash, Array, or scalar) instead of a string:
JSON.repair('{a: 1, b: [2, 3,]}', return_objects: true)
# => {"a" => 1, "b" => [2, 3]}
Canonical output
JSON.repair returns canonical JSON via JSON.generate. When the input is already valid, stdlib JSON.parse handles it; otherwise the repairer fixes it up and the result is re-serialized the same way. Either way, the output is the canonical form of the parsed value — whitespace is collapsed, numbers are normalized, \uXXXX escapes are decoded to literal characters, and objects with duplicate keys collapse to last-write-wins.
JSON.repair('{"a": 1}') # => '{"a":1}'
JSON.repair('{a:1}') # => '{"a":1}'
JSON.repair('2300e3') # => '2300000.0'
JSON.repair('{"a":1,"a":2}') # => '{"a":2}'
If you need the parsed Ruby value instead of a string, pass return_objects: true (covered above).
skip_json_loads: true skips the stdlib JSON.parse attempt and routes the input straight through the repairer. The output is the same; the option is purely a performance knob for callers who know their input will need repair.
Command line
The gem ships a json-repair executable. It reads from stdin or a file and writes to stdout, --output FILE, or back over the input file with --overwrite.
$ echo '{a:1,}' | json-repair
{"a":1}
$ json-repair broken.json
$ json-repair broken.json -o fixed.json
$ json-repair broken.json --overwrite
Run json-repair --help for the full list of options.
Development
After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.
Run bundle exec rake bench for a benchmark-ips regression baseline across four canned scenarios (valid mixed JSON, broken LLM-style output, a large array, deeply nested objects). The harness lives under benchmark/ and is not shipped in the published gem.
To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/sashazykov/json-repair-rb. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.
License
The gem is available as open source under the terms of the ISC License.
Code of Conduct
Everyone interacting in the JSON::Repair project's codebases, issue trackers, chat rooms, and mailing lists is expected to follow the code of conduct.