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Why are we templating YAML?

leebriggs.co.uk

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Re: Why are we templating YAML?

#111

Post by Waterluvian »

joeduffy wrote: post #57

My belief is that we've been slowly building up to using general purpose languages, one small step at a time, throughout the infrastructure as code, DevOps, and SRE journeys this past 10 years. INI files, XML, JSON, and YAML aren't sufficiently expressive -- lacking for loops, conditionals, variable references, and any sort of abstraction -- so, of course, we add templates to it. But as the author (IMHO rightfully) p…

In ROS we have these XML launch files that are just awful. They have enough features to be a really bad programming language for configuring and launching (often conditionally) numerous robot software nodes.

In ROS2 the launchfile can now just be a Python script. Very much learned all this the hard way and the solution was to just support Python. I think it's brilliant.

Re: Why are we templating YAML?

#112

Post by Aeolun »

zaphar wrote: post #110

Wholly agree with this which is why I've been experimenting with a project similar in goals to jsonnet as a side project of my own. I didn't know about jsonnet when I started or I'd probably have just used/contributed to that instead. Why template yaml when you could just generate it? Or generate json, or toml, or xml, or environment variables...

If you are generating it, why use it at all?

Re: Why are we templating YAML?

#113

Post by erikpukinskis »

rauhl wrote: post #97
joeduffy wrote: post #57

My belief is that we've been slowly building up to using general purpose languages, one small step at a time, throughout the infrastructure as code, DevOps, and SRE journeys this past 10 years. INI files, XML, JSON, and YAML aren't sufficiently expressive -- lacking for loops, conditionals, variable references, and any sort of abstraction -- so, of course, we add templates to it. But as the author (IMHO rightfully) p…

> My belief is that we've been slowly building up to using general purpose languages, one small step at a time, throughout the infrastructure as code, DevOps, and SRE journeys this past 10 years. I think that you’re right, and I think it’s great, because we have a programming model in which code is data and data is code: Lisp & S-expressions. It’d be downright awesome to have a Lisp-based system which used dynamic sc…

You don’t need code-is-data for what your parent is describing. All you need is code that outputs data. Or even better, code that initiates contact with other code.

The only requirement is a commitment to doing things imperatively in a real programming language. It’s hard to resist the temptation to do things declaratively (because it’s easier to imagine a declarative interface that describes your problem than an abstraction of the procedure which will solve it) but you are never forced to.

Re: Why are we templating YAML?

#114

Post by thanatropism »

chriswarbo wrote: post #84
ekianjo wrote: post #66

Earlier quoted context omitted.

a raw YAML file is readable with your eyes. A Json file needs to be prettified before you go thru it. Json is good for APIs but is not made for readibility.

We must disagree with what "readable" means then. I find JSON readable (as long as it's nicely layed out, e.g. by piping through 'jq "."'), in the sense that I can skim over the structure looking for [/]/{/}/". If I want to read some of the content, like a string, I just need to read '\"' as '"' and '\\' as '\', which is a small constant cost per (usually rare) occurrence. With YAML it's difficult to even know the st…

That's what syntax highlighting is for.

I use notepad++ for YAML. Besides coloring what it thinks I'm thinking, it displays vertical lines corresponding to the indentation levels.

(I prefer INI/TOML whenever I can help it; hierarchies in TOML are so counterintuitive that it incentivizes a simple flat structure. But then, some things are irremediably hierarchical)

Re: Why are we templating YAML?

#115

Post by krapp »

hannasanarion wrote: post #108
krferriter wrote: post #86

Earlier quoted context omitted.

Yeah this is a huge selling point of YAML. JSON should have comments added to the spec. The other benefit to YAML is human readability, which is usually better in YAML compared to JSON. A specific glaring example of this is when there are long string-literal snippets inside the document, in YAML this is massively more readable than in JSON.

JSON shouldn't have comments added to the spec, because people shouldn't be trying to read or write JSON. It's an application interchange language, meant to be written and read by machines. YAML is a markup language, meant to be written and read by people. Ever notice how most YAML libraries don't even have a "dump" function?

>It's an application interchange language, meant to be written and read by machines.

Not entirely true, JSON is based on Javascript objects, it was meant to be written and read by humans just like Javascript, INI or any other basic serialized data format, or text-based programming language. If JSON were truly never meant to never be viewed or edited by human beings, it would have been published as bytecode.

Re: Why are we templating YAML?

#116

Post by basil-rash »

bamboozled wrote: post #63
illumin8 wrote: post #55

Earlier quoted context omitted.

I generally dislike languages like YAML or Python where whitespace matters, and can break your code, however, YAML is way more easily human readable than JSON, so I started to appreciate it for readability purposes. I guess YMMV, but after you've used both YAML and JSON for a while, you might appreciate YAML a little bit more.

The killer feature for me over JSON is comment support, it's definitely useful to add todo comments etc.

You can just use JSON with comments though. If you have sufficient control over the technology in question to be able to completely change it to a YAML parser, surely you can change it to be a JSON+Comment parser too. See: VS Code's config files.

Re: Why are we templating YAML?

#117

Post by thanatropism »

pytester wrote: post #87
chriswarbo wrote: post #64

Earlier quoted context omitted.

> If you have been around long enough you still remember the world that was excited about XML and templating it using XSLT. As a hindsight it was a horrible world. I actually really like the idea behind XSLT: machine-friendly, human-tolerable, structured data + declarative rules for turning that data into a display, or a report, or whatever else. The execution was horrible though: incredibly verbose, lots of overcomp…

XSLT was one in a litany of domain specific languages (ant, apache rewrite rules, latex macros, etc.) that evolved towards turing completeness because that's what the problem space demanded. In most if not all of these cases an existing and well designed turing complete programming language would likely have better served them.

There was a post on HN a few weeks back to the effect that it's rather easy for Turing completeness to emerge accidentally. I wish I remembered more specifics so I could find it again.

Re: Why are we templating YAML?

#118

Post by basil-rash »

ekianjo wrote: post #66
chriswarbo wrote: post #59

Earlier quoted context omitted.

> YAML is way more easily human readable than JSON, so I started to appreciate it for readability purposes. > I guess YMMV, but after you've used both YAML and JSON for a while, you might appreciate YAML a little bit more. I've used JSON a lot, and XML and s-expressions and MessagePack and ini and YAML and a whole bunch of other formats. I usually have to fire up Google to read YAML. YAML is the only one where I rout…

a raw YAML file is readable with your eyes. A Json file needs to be prettified before you go thru it. Json is good for APIs but is not made for readibility.

Is it really though? The implicit typecasting gives rise to very unexpected results, that you'd never get with JSON. See: https://hitchdev.com/strictyaml/why/implicit-typing-removed/

Re: Why are we templating YAML?

#119

Post by jtdev »

Cyph0n wrote: post #106
tfinch wrote: post #54

Earlier quoted context omitted.

also this is probably a nicer intro https://dhall-lang.org/

What is up with the strange comma positioning? I assume that’s just a stylistic choice?

It allows each line to be completely independent of it’s neighbors; you can comment and/or add lines without needing to touch neighboring lines. Also, it makes it visually easy to spot missing commas. Give it a try sometime, it’s actually quite nice.

Re: Why are we templating YAML?

#120

Post by basil-rash »

necubi wrote: post #73
svnpenn wrote: post #51

Earlier quoted context omitted.

god those examples are ugly - commas at the beginning of a line? mismatched brace styles?

It's a haskell thing. The main advantage is that each line is independent. You can comment out a line or add a line at the end without modifying anything else.

Each line is not independent: you cannot comment out the first line. A better approach is to allow trailing commas. (I suppose you could allow leading commas, does Haskell support this?)
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