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|
{ pkgs, depot, lib, ... }:
let
# import the dhall file as nix expression via dhall-nix.
# Converts the normalized dhall expression to a nix file,
# puts it in the store and imports it.
# Types are erased, functions are converted to nix functions,
# unions values are nix functions that take a record of match
# functions for their alternatives.
# TODO: document better
importDhall =
{
# Root path of the dhall file tree to import (will be filtered by files)
root
, # A list of files which should be taken from `root` (relative paths).
# This is for minimizing the amount of things that have to be copied to the store.
# TODO: can you have directory prefixes?
files
, # The path of the dhall file which should be evaluated, relative to `root`, has to be in `files`
main
, # List of dependencies (TODO: what is a dependency?)
deps
, # dhall type of `main`, or `null` if anything should be possible.
type ? null
}:
let
src =
depot.users.Profpatsch.exactSource
root
# exactSource wants nix paths, but I think relative paths
# as strings are more intuitive.
(
let abs = path: toString root + "/" + path;
in ([ (abs main) ] ++ (map abs files))
);
cache = ".cache";
cacheDhall = "${cache}/dhall";
hadTypeAnnot = type != null;
typeAnnot = lib.optionalString hadTypeAnnot ": ${type}";
convert = pkgs.runCommandLocal "dhall-to-nix" { inherit deps; } ''
mkdir -p ${cacheDhall}
for dep in $deps; do
${pkgs.xorg.lndir}/bin/lndir -silent $dep/${cacheDhall} ${cacheDhall}
done
export XDG_CACHE_HOME=$(pwd)/${cache}
# go into the source directory, so that the type can import files.
# TODO: This is a bit of a hack hrm.
cd "${src}"
${if hadTypeAnnot then ''
printf '%s' ${lib.escapeShellArg "${src}/${main} ${typeAnnot}"} \
| ${pkgs.dhall-nix}/bin/dhall-to-nix \
> $out
''
else ''
printf 'No type annotation given, the dhall expression type was:\n'
${pkgs.dhall}/bin/dhall type --file "${src}/${main}"
printf '%s' ${lib.escapeShellArg "${src}/${main}"} \
| ${pkgs.dhall-nix}/bin/dhall-to-nix \
> $out
''}
'';
in
import convert;
# read dhall file in as JSON, then import as nix expression.
# The dhall file must not try to import from non-local URLs!
readDhallFileAsJson = dhallType: file:
let
convert = pkgs.runCommandLocal "dhall-to-json" { } ''
printf '%s' ${lib.escapeShellArg "${file} : ${dhallType}"} \
| ${pkgs.dhall-json}/bin/dhall-to-json \
> $out
'';
in
builtins.fromJSON (builtins.readFile convert);
in
{
inherit
importDhall
readDhallFileAsJson
;
}
|
