6 ms·

I'm sorry, can someone explain why one would want to translate from one data description language to another (Pkl -> JSON, or whatever)? Why not just write JSON

I'm sorry, can someone explain why one would want to translate from one data description language to another (Pkl -> JSON, or whatever)? Why not just write JSON (or whatever) to begin with?

deleted 3y ago
[deleted]
avianlyric 3y ago
Because Pkl makes it trivial to write templates and transforms. So you can write a Pkl schema that only requires a minimum set of fields, then auto generate a complete configuration. This is most useful when dealing with tools like k8s where deploying a single application might involve 3-10 separate manifests (Deployment, Service, NetworkPolicy, HttpRoute, Autoscaler etc etc). With Pkl you can easily write a simple template that only requests the minimum needed to define an “app” (e.g. name, namespace, mixins for sidecars) and have Pkl generate all the needed manifests for you. Really Pkl should be seen as a language for quickly building templating tools like Helm. But with type safety by default, and no need for horrible indent hacks.
pjerem 3y ago
Just scroll a little further. It’s not just another syntax for config files.
hiAndrewQuinn 3y ago
Well, Dhall provides something between JSON and a Turing complete language that can make a lot of configuration much quicker to write, if you can hack the functional syntax. Pkl is probably a similar concept. http://dhall-lang.org/ http://dhall-lang.org/
- kccqzy 3y ago
  I love Dhall. It's purposefully not Turing complete (which is somewhat difficult to achieve in a language design) and I love that fact.
viraptor 3y ago
Json lacks comments, templating, evaluation, types, and lots of other features. Having something generating a valid config is great, especially if you're generating multiple configs in different format from the same place. For example being able to configure SSH, nginx and some other services from nixos config is amazing.
isodev 3y ago
In general (not just limited to Pkl), I think the advantage is that you get IDE support like autocomplete and compile time checks. Pkl seems to borrow some features from JSONSchema/SHACL for example where one can also add validations like "value must be bigger than 20 and lower than 100" so when you configure a component incorrectly, it can throw a good error message before deployment.
BiteCode_dev 3y ago
Because there are a thousand ways to describe the same thing in JSON. This: city = { "id": 3, "name": "Foo", "lat": 3.555, "long": 4.11, } Is the same as: city = { "id": "3", "name": "Foo", "coordinates": [3.555, 4.11] } But you want to normalize that. Something like Cuelang will: - Define the schema that will let you know what you should put inside. - Allow you to inflate that schema into a full file, providing only the values. - Will generate always a correct file, with no typo, or format error. - Will check that the data is correct and tell you if there are any errors. - Is note theoretically tied to a particular run time or stack.
- worthless-trash 3y ago
  In your example, how is this different than incorrectly creating the data structure in any format ? I'll be looking into cue, but how does it solve that problem ?
- styfle 3y ago
  Sounds like a job for JSON Schema https://json-schema.org https://json-schema.org
  - bpicolo 3y ago
    Jumping back and forth between a JSON schema and writing valid JSON is not a very fun task
Gravityloss 3y ago
Writing raw JSON is very error prone and you have to repeat yourself a lot. I think everyone who has worked with it has had some surprises, I certainly have. Similar to why do we write Python instead of assembly, or why do relational databases typically have things like datatypes and constraints?
mlindner 3y ago
The amount of problems I've had with JSON in my career makes me think almost anything could be better than it. There's so many weird edge cases in the JSON spec that you can hit that it just becomes endless levels of hair pulling.
- cerved 3y ago
  which edge cases?
- g4zj 3y ago
  Can you share some examples?
- garethrowlands 3y ago
  Have you tried YAML? :-)
  - mrkeen 3y ago
    NOrway, I haven't.
shuafajdn 3y ago
[dead]

I'm sorry, can someone explain why one would want to translate from one data description language to another (Pkl -> JSON, or whatever)? Why not just write JSON (or whatever) to begin with?

deleted 3y ago

[deleted]

avianlyric 3y ago

Because Pkl makes it trivial to write templates and transforms. So you can write a Pkl schema that only requires a minimum set of fields, then auto generate a complete configuration. This is most useful when dealing with tools like k8s where deploying a single application might involve 3-10 separate manifests (Deployment, Service, NetworkPolicy, HttpRoute, Autoscaler etc etc). With Pkl you can easily write a simple template that only requests the minimum needed to define an “app” (e.g. name, namespace, mixins for sidecars) and have Pkl generate all the needed manifests for you. Really Pkl should be seen as a language for quickly building templating tools like Helm. But with type safety by default, and no need for horrible indent hacks.

pjerem 3y ago

Just scroll a little further. It’s not just another syntax for config files.

hiAndrewQuinn 3y ago

Well, Dhall provides something between JSON and a Turing complete language that can make a lot of configuration much quicker to write, if you can hack the functional syntax. Pkl is probably a similar concept. http://dhall-lang.org/ http://dhall-lang.org/

kccqzy 3y ago
I love Dhall. It's purposefully not Turing complete (which is somewhat difficult to achieve in a language design) and I love that fact.

viraptor 3y ago

Json lacks comments, templating, evaluation, types, and lots of other features. Having something generating a valid config is great, especially if you're generating multiple configs in different format from the same place. For example being able to configure SSH, nginx and some other services from nixos config is amazing.

isodev 3y ago

In general (not just limited to Pkl), I think the advantage is that you get IDE support like autocomplete and compile time checks. Pkl seems to borrow some features from JSONSchema/SHACL for example where one can also add validations like "value must be bigger than 20 and lower than 100" so when you configure a component incorrectly, it can throw a good error message before deployment.

BiteCode_dev 3y ago

Because there are a thousand ways to describe the same thing in JSON. This: city = { "id": 3, "name": "Foo", "lat": 3.555, "long": 4.11, } Is the same as: city = { "id": "3", "name": "Foo", "coordinates": [3.555, 4.11] } But you want to normalize that. Something like Cuelang will: - Define the schema that will let you know what you should put inside. - Allow you to inflate that schema into a full file, providing only the values. - Will generate always a correct file, with no typo, or format error. - Will check that the data is correct and tell you if there are any errors. - Is note theoretically tied to a particular run time or stack.

worthless-trash 3y ago
In your example, how is this different than incorrectly creating the data structure in any format ? I'll be looking into cue, but how does it solve that problem ?
styfle 3y ago
Sounds like a job for JSON Schema https://json-schema.org https://json-schema.org
- bpicolo 3y ago
  Jumping back and forth between a JSON schema and writing valid JSON is not a very fun task

Gravityloss 3y ago

Writing raw JSON is very error prone and you have to repeat yourself a lot. I think everyone who has worked with it has had some surprises, I certainly have. Similar to why do we write Python instead of assembly, or why do relational databases typically have things like datatypes and constraints?

mlindner 3y ago

The amount of problems I've had with JSON in my career makes me think almost anything could be better than it. There's so many weird edge cases in the JSON spec that you can hit that it just becomes endless levels of hair pulling.

cerved 3y ago
which edge cases?
g4zj 3y ago
Can you share some examples?
garethrowlands 3y ago
Have you tried YAML? :-)
- mrkeen 3y ago
  NOrway, I haven't.

shuafajdn 3y ago

[dead]