84 lines
2.5 KiB
Nix
84 lines
2.5 KiB
Nix
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{ haskell, haskellPackages, lib, lndir, runCommand, writeText }:
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{ name
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# Expressions to add to the cache before interpreting the code
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, dependencies ? []
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# A Dhall expression
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#
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# Carefully note that the following expression must be devoid of uncached HTTP
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# imports. This is because the expression will be evaluated using an
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# interpreter with HTTP support disabled, so all HTTP imports have to be
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# protected by an integrity check that can be satisfied via cached
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# dependencies.
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#
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# You can add a dependency to the cache using the preceding `dependencies`
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# option
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, code
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# `buildDhallPackage` can include both a "source distribution" in
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# `source.dhall` and a "binary distribution" in `binary.dhall`:
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#
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# * `source.dhall` is a dependency-free αβ-normalized Dhall expression
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#
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# * `binary.dhall` is an expression of the form: `missing sha256:${HASH}`
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#
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# This expression requires you to install the cache product located at
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# `.cache/dhall/1220${HASH}` to successfully resolve
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#
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# By default, `buildDhallPackage` only includes "binary.dhall" to conserve
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# space within the Nix store, but if you set the following `source` option to
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# `true` then the package will also include `source.dhall`.
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, source ? false
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}:
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let
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# `buildDhallPackage` requires version 1.25.0 or newer of the Haskell
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# interpreter for Dhall. Given that the default version is 1.24.0 we choose
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# the latest available version instead until the default is upgraded.
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#
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# HTTP support is disabled in order to force that HTTP dependencies are built
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# using Nix instead of using Dhall's support for HTTP imports.
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dhall =
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haskell.lib.justStaticExecutables
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(haskell.lib.appendConfigureFlag
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haskellPackages.dhall_1_29_0
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"-f-with-http"
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);
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file = writeText "${name}.dhall" code;
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cache = ".cache";
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cacheDhall = "${cache}/dhall";
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sourceFile = "source.dhall";
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in
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runCommand name { inherit dependencies; } ''
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set -eu
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mkdir -p ${cacheDhall}
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for dependency in $dependencies; do
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${lndir}/bin/lndir -silent $dependency/${cacheDhall} ${cacheDhall}
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done
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export XDG_CACHE_HOME=$PWD/${cache}
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mkdir -p $out/${cacheDhall}
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${dhall}/bin/dhall --alpha --file '${file}' > $out/${sourceFile}
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SHA_HASH=$(${dhall}/bin/dhall hash <<< $out/${sourceFile})
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HASH_FILE="''${SHA_HASH/sha256:/1220}"
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${dhall}/bin/dhall encode --file $out/${sourceFile} > $out/${cacheDhall}/$HASH_FILE
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echo "missing $SHA_HASH" > $out/binary.dhall
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${lib.optionalString (!source) "rm $out/${sourceFile}"}
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''
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