jsonnet
pyyaml
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jsonnet | pyyaml | |
---|---|---|
48 | 16 | |
6,753 | 2,425 | |
1.0% | 1.3% | |
8.4 | 3.9 | |
6 days ago | 11 days ago | |
Jsonnet | Python | |
Apache License 2.0 | MIT License |
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jsonnet
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A Reasonable Configuration Language
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/
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Pkl, a Programming Language for Configuration
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)
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Introduction to Jsonnet: The YAML/JSON templating language
jsonnet cli: link
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10 Ways for Kubernetes Declarative Configuration Management
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.
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-❄️- 2023 Day 4 Solutions -❄️-
[Language: Jsonnet] (on GitHub)
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What Is Wrong with TOML?
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
- Show HN: Keep – GitHub Actions for your monitoring tools
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That people produce HTML with string templates is telling us something
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.
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TOML: Tom's Obvious Minimal Language
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/
- Jsonnet – The Data Templating Language
pyyaml
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Cython 3.0 Released
PyYAML knew about the breakage since january 2022[0], and nothing really happened. After a year and a half with lots of alphas and betas, I don't think there is much cython could do, short of fixing PyYAML themselves.
[0]: https://github.com/yaml/pyyaml/issues/601
- Cython v3 release breaking PyYAML install well used in Python ecosystem
- Cython and pyyaml is breaking many builds
- I'm needing a hand, I do not understand some (seemingly) simple Python stuff.
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is there any difference between using string.format() or an fstring?
They did finally change the default, in PyYAML 6, after many many bugs pointing out that their previous approach is broken (including one by yours truly), so the default is now safe.
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Using Rust to not have to touch Yaml in k8s land
Note some parsers, most notably pyyaml are still at yaml 1.1, because 13 years is just not enough time to update it.
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JSON is not a YAML subset
That part of the YAML 1.2 spec is in conflict with reality, though. The base of YAML 1.1 documents is large enough that a backwards-incompatible change to default behavior is for practical purposes impossible.
YAML 1.1 was released in 2005, and 1.2 in 2009 -- only four years later. But here we are, in 2022, and YAML 1.1 is still the default (in many cases, only) version supported. That's why the "Norway problem" persists -- it's not possible for the parser to know whether an un-versioned YAML document containing "a: no" should parse the same as {"a": false} or {"a": "no"}.
Python (PyYAML) doesn't support 1.2 yet: https://github.com/yaml/pyyaml/issues/116
Ruby (Psych) ditto -- I can't even find a tracking issue to enable it.
Go (go-yaml) is a mixture of YAML 1.1 and 1.2, depending on the author's preferences.
Also, as a rough guideline, you can't have a backwards-incompatible revision of a versioned spec declare that it's the new default version, because that breaks all existing users.
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I accidentally used YAML.parse instead of JSON.parse, and it worked?
Many parsers either default to YAML pre-1.2 or do not even expose a YAML 1.2 option. PyYAML has no 1.2 option, for example. So unless Ansible is using something other than PyYAML...
Relevant (open) PR: https://github.com/yaml/pyyaml/pull/555
- AttributeError: '_io.TextIOWrapper' object has no attribute 'items'
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Why doesn't yaml allow safe_dump for decimals?
Are you perhaps talking about decimal.Decimal? https://github.com/yaml/pyyaml/issues/255
What are some alternatives?
kube-libsonnet - Bitnami's jsonnet library for building Kubernetes manifests
confuse - painless YAML config files for Python
dhall-lang - Maintainable configuration files
strictyaml - Type-safe YAML parser and validator.
cue - CUE has moved to https://github.com/cue-lang/cue
yamllint - A linter for YAML files.
cue - The home of the CUE language! Validate and define text-based and dynamic configuration
marshmallow - A lightweight library for converting complex objects to and from simple Python datatypes.
json5 - JSON5 — JSON for Humans
python-strict-yaml-parsing - Examples of strict yaml parsing in python
cdk8s - Define Kubernetes native apps and abstractions using object-oriented programming
python-frontmatter - Parse and manage posts with YAML (or other) frontmatter