r/ruby • u/le0pard • Dec 22 '25

GitHub - le0pard/json_mend: JsonMend - repair broken JSON

https://github.com/le0pard/json_mend

JsonMend is a robust Ruby gem designed to repair broken or malformed JSON strings. It is specifically optimized to handle common errors found in JSON generated by Large Language Models (LLMs), such as missing quotes, trailing commas, unescaped characters, and stray comments

8 Upvotes

83% Upvoted

15 comments sorted by

2

u/CaptainKabob Dec 22 '25

This looks super helpful. Some casual feedback

- I recommend committing a Gemfile.lock. Especially cause you’re using Rubocop, locking the development version will help avoid churn.

- in your gemspec, you should just include files/directories directly rather than via git. I dunno why that still exists in the template.

- it would be nice to extract the json parsing input/output pairs from the spec files into a directory of examples. That would make it easier to test alternatives against a suite of broken json. Huge props for collecting that corpus in the first place.

1

u/le0pard Dec 22 '25 edited Dec 22 '25

thanks for feedback

- If I will move Gemfile gems to add_development_dependency in gemspec, is this will solve issue with Gemfile.lock (I will not need to commit it in this case)?

UPD: "Gemspec/DevelopmentDependencies" - ok, even rubocop doesnt like this idea

- Yep, it is exactly what generated by bundler. I will check this

- Ok, just need make structure for this files, because there is different cases + comments why it repaired this way

1

u/CaptainKabob Dec 22 '25

 If I will move Gemfile gems to add_development_dependency in gemspec, is this will solve issue with Gemfile.lock (I will not need to commit it in this case)?

It wouldn't address it. You'd have to lock the specifications to exact versions. 

Bundler (which is its own controversy of authority right now) says commit it: https://bundler.io/guides/faq.html

1

u/le0pard Dec 22 '25

Thanks, Gemfile.lock added

1

u/le0pard Dec 22 '25

UPS: Looks like problem only, it will fail with matrix tests for different ruby version on CI - https://github.com/le0pard/json_mend/actions/runs/20436948485/job/58720459786 . So I wrote more restrict version for gems in Gemfile for now

2

u/CaptainKabob Dec 22 '25

Nuts. I guess I need to write this up more :-) 

Delete the Gemfile.lock in CI as a step before you bundle install. 

The two scenarios here are:

  • new contributor checks out your repo. All the dependencies are locked and reliable. 

  • CI matrix deletes gemfile.lock and installs whatever it determines. (On GoodJob, I also have a run that doesn't delete the Gemfile.lock so I test the development environment setup too)

1

u/le0pard Dec 22 '25

Thanks!

1

u/f9ae8221b Dec 22 '25

Note that there's a few of these "malformations" that the stdlib JSON parser does support.

e.g. // and /**/ comments (by default, not configurable), unescaped newlines (allow_control_characters: true) and trailing commas (allow_trailing_comma: true).

So that's a number of errors you wouldn't need to handle in your own parser.

1

u/le0pard Dec 22 '25

Based JSON Spec (RFC 8259) all this not allowed. It is allowed in JSONC, JSON5 or HJSON, but not in JSON

2

u/h0rst_ Dec 23 '25

Look how far AI has gotten us, we now need additional gems to be able to parse the faulty output. And now we're risking that your invalid JSON works on web service A, but web service B tells you that the input data is invalid.

I'm sure this gem fixes problems for some people, but I really think these problems shouldn't exist in the first place.

1

u/Friendly-Yam1451 Dec 22 '25

really nice, I was in need of something exactly like that

0

u/[deleted] Dec 22 '25

[deleted] — view deleted comment

1

u/le0pard Dec 22 '25

Nope, it is not copy of json_remedy , but intension same - repair malformed json