jsonnet: Jsonnet implementaton in pure Haskell

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Please see the README on GitHub at https://github.com/moleike/jsonnet-haskell#readme

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0.1.0.0

Versions [RSS]	0.1.0.0, 0.2.0.0, 0.3.0.0, 0.3.0.1, 0.3.1.1, 0.4.0.0 (info)
Change log	CHANGELOG.md
Dependencies	aeson (>=2.2 && <2.3), base (>=4.20 && <4.22), binary (>=0.8.8 && <0.9), bytestring (>=0.11 && <0.13), containers (>=0.6.2 && <0.8), data-fix (>=0.3.1 && <0.4), directory (>=1.3.6 && <1.4), exceptions (>=0.10.4 && <0.11), filepath (>=1.4.2 && <1.6), jsonnet, lens (>=5.0.1 && <5.4), megaparsec (>=9.5 && <9.8), mtl (>=2.2.2 && <2.4), optparse-applicative (>=0.16.1 && <0.19), parser-combinators (>=1.2.1 && <1.4), prettyprinter (>=1.7.0 && <1.8), scientific (>=0.3.7 && <0.4), template-haskell (>=2.16.0 && <2.23), text (>=2.0 && <2.2), th-lift-instances (>=0.1.18 && <0.2), th-utilities (>=0.2.4.2 && <0.3), transformers-compat (>=0.6.6 && <0.8), unbound-generics (>=0.4.3 && <0.5), unordered-containers (>=0.2.14 && <0.3), vector (>=0.12.3 && <0.14) [details]
License	BSD-3-Clause
Copyright	2020 Alexandre Moreno
Author	Alexandre Moreno
Maintainer	alexmorenocano@gmail.com
Category	Compiler
Home page	https://github.com/moleike/haskell-jsonnet#readme
Bug tracker	https://github.com/moleike/haskell-jsonnet/issues
Source repo	head: git clone https://github.com/moleike/haskell-jsonnet
Uploaded	by moleike at 2025-04-09T19:22:06Z
Distributions
Executables	hs-jsonnet
Downloads	794 total (4 in the last 30 days)
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Status	Docs uploaded by user Build status unknown [no reports yet]

Readme for jsonnet-0.4.0.0

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haskell-jsonnet

A full-fledged Haskell implementation of the Jsonnet spec. For an introduction to the language itself, see the tutorial or language reference. We are using the same test suite used in the offical C++ and Go implementation (which is fairly comprehensive).

Progress

Here is the implementation status of the main language features:

Build

Using the stack build tool:

% git clone github.com/moleike/haskell-jsonnet.git
% cd haskell-jsonnet
% stack build

Install

% stack install # to install

Usage

% hs-jsonnet --help
Usage: hs-jsonnet [-v|--version] [-e|--exec] [<filename>] 
                  [-o|--output-file <filename>] [-S|--string] 
                  [-V|--ext-str VAR=VALUE] [--ext-str-file FILE] 
                  [--ext-code VAR=EXPR] [--ext-code-file FILE]

Available options:
  -v,--version             Print version of the program
  -h,--help                Show this help text
  -e,--exec                Treat filename as code
  <filename>               Jsonnet source file or stdin
  -o,--output-file <filename>
                           Write to the output file rather than stdout
  -S,--string              Expect a string, manifest as plain text
  -V,--ext-str VAR=VALUE   External string variable
  --ext-str-file FILE      External string variable as file
  --ext-code VAR=EXPR      External code variable
  --ext-code-file FILE     External code variable as file

Output formats

By default Jsonnet programs evaluate to a JSON document, serialized using aeson.

The std library provides several methods to output other formats, e.g. to generate a Yaml stream instead:

% hs-jsonnet -S -e "std.manifestYamlStream(['a', 1, []])"
---
"a"
---
1
---
[]
...

Note the we need to use the option -S to output a verbatim string, instead of default JSON.

Similarly, to output prettified JSON:

% cat pretty.jsonnet 
std.manifestJsonEx(
{
    x: [1, 2, 3, true, false, null,
        "string\nstring"],
    y: { a: 1, b: 2, c: [1, 2] },
}, "    ")

% hs-jsonnet -S pretty.jsonnet
{
    "x": [
        1,
        2,
        3,
        true,
        false,
        null,
        "string\nstring"
    ],
    "y": {
        "a": 1,
        "b": 2,
        "c": [
            1,
            2
        ]
    }
}

See the Standard library documentation for more details.

Benchmarks

Preliminary results using the benchmarks here for comparison.

Contributing

See CONTRIBUTING.md.

Acknowledgments

I took inspiration from Expresso, hnix, fixplate, Disco, and numerous other libraries. Thanks to their authors.

License

Copyright © 2020–present Alexandre Moreno