hpack-dhall: hpack's dhalling

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Work with hpack's top-level fields in a Dhall record with the following executables;


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Properties

Versions0.1.0, 0.2.0, 0.3.0, 0.4.0, 0.4.0, 0.5.0
Change logchangelog.md
Dependenciesaeson, aeson-pretty, base (==4.*), bytestring, dhall (>=1.18.0), dhall-json (>=1.2.4), filepath, hpack (>=0.31.0), megaparsec (>=7.0.1), microlens, optparse-applicative, prettyprinter, text, transformers, yaml [details]
LicenseBSD-3-Clause
Copyright© 2018 Phil de Joux, © 2018 Block Scope Limited
MaintainerPhil de Joux <phil.dejoux@blockscope.com>
CategoryDevelopment
Home pagehttps://github.com/blockscope/hpack-dhall#readme
Bug trackerhttps://github.com/blockscope/hpack-dhall/issues
Source repositoryhead: git clone https://github.com/blockscope/hpack-dhall
Executablesdhall-hpack-yaml, dhall-hpack-json, dhall-hpack-dhall, dhall-hpack-cabal
UploadedMon Oct 29 19:44:12 UTC 2018 by philderbeast

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Readme for hpack-dhall-0.4.0

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hpack-dhall

Build Status hackage release Dependencies of latest version on Hackage

Haskell package descriptions in Dhall.

This package named hpack-dhall as described in package.dhall.

{ name =
    "hpack-dhall"
...
, library =
    { exposed-modules = "Hpack.Dhall" }
, executables =
    { dhall-hpack-cabal = ...
    , dhall-hpack-json = ...
    , dhall-hpack-yaml = ...
    , dhall-hpack-dhall = ...
    }
}

This .cabal creating executable can be run over its own package description;

> stack install --stack-yaml=stack-8.4.4.yaml
...
Copied executables to /.../hpack-dhall/__bin:
- dhall-hpack-cabal
- dhall-hpack-dhall
- dhall-hpack-json
- dhall-hpack-yaml

> __bin/dhall-hpack-cabal package.dhall
hpack-dhall.cabal is up-to-date

> __bin/dhall-hpack-cabal --force package.dhall
generated hpack-dhall.cabal

Using one of the golden tests for example, there are executables to show the dhall with the imports made as well as json and yaml equivalents;

> __bin/dhall-hpack-dhall test/golden/hpack-dhall-cabal/empty-package.dhall
{ name = "empty-package" }

> __bin/dhall-hpack-json test/golden/hpack-dhall-cabal/empty-package.dhall
{
    "name": "empty-package"
}

> __bin/dhall-hpack-yaml test/golden/hpack-dhall-cabal/empty-package.dhall
name: empty-package

By going from hpack package fields to cabal package properties, we are not required to state what can be inferred or defaulted, easing the burden of completing a package description by hand. For example other-modules can be inferred by taking the set difference between modules on disk and the set of exposed-modules.

By using an hpack-like Dhall dialect here rather than the YAML of hpack we're able to;

Imports and Functions

With this safer and more capable alternative input format for hpack, we're able to simply describe the package and by using imports and functions we can do more such as configuring linting;

> cat default-extensions.dhall
{ default-extensions =
    [ "DataKinds"
    , "DeriveFunctor"
    ...
    , "TupleSections"
    , "UndecidableInstances"
    ]
}

> cat hlint.dhall
    let Prelude/List/map =
          https://raw.githubusercontent.com/dhall-lang/Prelude/35deff0d41f2bf86c42089c6ca16665537f54d75/List/map

in  let defs = ./default-extensions.dhall

in  let f = λ(s : Text) → "-X" ++ s

in  { arguments = Prelude/List/map Text Text f defs.default-extensions }

> dhall-to-yaml < ./hlint.dhall > ./.hlint.yaml

> cat .hlint.yaml
arguments:
- -XDataKinds
- -XDeriveFunctor
...
- -XTupleSections
- -XUndecidableInstances

We can pull those same default-extensions into a package description;

> cat package.dhall
    let defs = ./defaults.dhall

in    defs
    ⫽ ./default-extensions.dhall
    ⫽ { name =
          "flight-units"
    ...
      , github =
          "blockscope/flare-timing/units"
    ...
      , dependencies =
            defs.dependencies
          # [ "numbers"
            , "fixed"
            , "bifunctors"
            , "text"
            , "formatting"
            , "uom-plugin"
            , "siggy-chardust"
            ]
    ...
      }

Formatting

We can consistently format package.dhall and other *.dhall imports using dhall;

> stack install dhall --stack-yaml=stack-dhall.yaml
> __bin/dhall format --inplace package.dhall