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