json VS jsonnet

I have not done a "desktop" program in 25+ years and never using C++ (or C), since then I'm mostly a web developer (PHP,Elixir, JS, Kotlin etc).

I'm currently doing a C++ audio plugin with the Juce framework.

This website has been a good resource, alongside https://www.learncpp.com

But I was actually close to give up before using those two things:

- https://github.com/nlohmann/json : my plugin use a json api backend and the Juce json implementation is atrocious (apparently because of being born in previous c++ version), but this library is GREAT.

- ChatGPT 4. I'm not sure I would have "succeeded" without it, at least not in a reasonable time frame. ChatGPT 3.5 is slow and does not give good results for my use case but 4 is impressive. And I use in a very dumb way, just posing question in the web UI. I probably could have it directly in MSVC?

Also I must say, for all its flaws, I have a renewed appreciation for doing UI on the web ;)

https://github.com/nlohmann/json works well for me

cmake_minimum_required(VERSION 3.15) project(xrpc++ DESCRIPTION "C++ AT Protocol XRPC library" VERSION 1.0.0 LANGUAGES CXX) include(FetchContent) FetchContent_Declare(cpr GIT_REPOSITORY https://github.com/libcpr/cpr.git GIT_TAG 2553fc41450301cd09a9271c8d2c3e0cf3546b73) # The commit hash for 1.10.x. Replace with the latest from: https://github.com/libcpr/cpr/releases FetchContent_MakeAvailable(cpr) FetchContent_Declare(json URL https://github.com/nlohmann/json/releases/download/v3.11.2/json.tar.xz) FetchContent_MakeAvailable(json) add_library(${PROJECT_NAME} SHARED src/lexicon.cpp src/xrpc.cpp ) target_link_libraries(${PROJECT_NAME} PRIVATE cpr::cpr) target_link_libraries(${PROJECT_NAME} PRIVATE nlohmann_json::nlohmann_json) set_target_properties(${PROJECT_NAME} PROPERTIES VERSION ${PROJECT_VERSION}) set_target_properties(${PROJECT_NAME} PROPERTIES SOVERSION 1) target_include_directories(${PROJECT_NAME} PUBLIC include) set(CMAKE_BUILD_TYPE debug)

FetchContent_Declare(json URL https://github.com/nlohmann/json/releases/download/v3.11.2/json.tar.xz) FetchContent_MakeAvailable(json)

Here is one popular C++ library (nlohmann/json) removing its use.

Before going into binary serialization I suggest you to get comfortable with serialization to text. You can try to write your data to text files and read them in again. Then after you get an idea of how this works you can try to use a library that writes to XML or json, e.g. nlohmann json

Download the single header file json.hpp from https://github.com/nlohmann/json/releases and place it in your project directory or an include directory.

Exemple of a JSON library: https://github.com/nlohmann/json (For XML, there's tinyxml)

jsonnet[1] and kapitan[2] are the tools I currently use. Their learning curve is not optimal (and I tried to contribute to smoothen it with a jsonnet course[3] and a 'get started wit kapitan' blog post[4]), but once used to it it's hard to do without, and their combination makes them even more useful (esp. if you deploy K8s).

In Ruud's case, Jsonnet might have been worth looking at as Hashicorp tools can be configured with json in addition to HCL. But that would have been less fun I guess ;-)

I hope for Ruud it finds its niche, there's quite some competition in this field!

1: https://jsonnet.org/

Kubernetes config is a decent example. I had ChatGPT generate a representative silly example -- the content doesn't matter so much as the structure:

https://gist.github.com/cstrahan/528b00cd5c3a22e3d8f057bb1a7...

Now consider 100s (if not 1000s) of such files.

I haven't given Pkl an in depth look yet, but I can say that the Industry Standard™ of "simple YAML" + string substitution (with delicate, error prone indentation -- since YAML is indentation sensitive) is easily beat by any of:

- https://jsonnet.org/

- https://nickel-lang.org/

- https://nixos.org/manual/nix/stable/language/index.html

- https://dhall-lang.org/

- (insert many more here, probably including Pkl)

jsonnet cli: link

Jsonnet: A data template language implemented in C++, suitable for application and tool developers, can generate configuration data and organize, simplify and manage large configurations without side effects.

[Language: Jsonnet] (on GitHub)

Maybe you'd like jsonnet: https://jsonnet.org/

I find it particularly useful for configurations that often have repeated boilerplate, like ansible playbooks or deploying a bunch of "similar-but" services to kubernetes (with https://tanka.dev).

Dhall is also quite interesting, with some tradeoffs: https://dhall-lang.org/

A few years ago I did a small comparison by re-implementing one of my simpler ansible playbooks: https://github.com/retzkek/ansible-dhall-jsonnet

Apologies for the lack of context, and for missing this comment until today.

Both are tools for defining kubernetes manifests (which are YAML) in a reusable manner.

Jsonnet is a formally specified extension of JSON. It’s essentially a functional programming language (w/some object oriented features) that generates config files in JSON/YAML/etc, so it’s straightforward to determine whether an input file is valid, and to throw an error that points to an exact line if it’s not. It has a high learning curve, especially for people whose only experience is with imperative languages.

https://jsonnet.org/

Helm charts also generate YAML/JSON config files, but they use Go templating. This is easier and faster to understand, since it’s mostly string substitution and not much logic (there’s conditionals, iterators, and very basic helper functions). Unfortunately a simple typo or mistake can cause errors that are difficult to diagnose (the message may indicate a problem far away in code from the actual mistake). It can also generate output that’s valid according to the string templating rules, but not what was intended, which can be very confusing to debug.

Despite these shortcomings, the vast majority of kubernetes applications are distributed as helm charts. I understand why things ended up this way, but I still wish it were more common for people to invest the upfront effort to learn the superior tool, so it could be more widespread.

I like Google's Jsonnet [1], which has all of this except for 4.

Jsonnet is quite mature, with fairly wide language adoption, and has the benefit of supporting expressions, including conditionals, arithmetic, as well as being able to define reusable blocks inside function definitions or external files.

It's not suitable as a serialization format, but great for config. It's popular in some circles, but I'm sad that it has not reached wider adoption.

[1] https://jsonnet.org/