tvl-depot/tools/nixery/prepare-image/load-pkgs.nix

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# Copyright 2022 The TVL Contributors
# SPDX-License-Identifier: Apache-2.0
# Load a Nix package set from one of the supported source types
# (nixpkgs, git, path).
{ srcType, srcArgs, importArgs ? { } }:
with builtins;
let
# If a nixpkgs channel is requested, it is retrieved from Github (as
# a tarball) and imported.
fetchImportChannel = channel:
let
url =
"https://github.com/NixOS/nixpkgs/archive/${channel}.tar.gz";
in
import (fetchTarball url) importArgs;
# If a git repository is requested, it is retrieved via
# builtins.fetchGit which defaults to the git configuration of the
# outside environment. This means that user-configured SSH
# credentials etc. are going to work as expected.
fetchImportGit = spec: import (fetchGit spec) importArgs;
# No special handling is used for paths, so users are expected to pass one
# that will work natively with Nix.
importPath = path: import (toPath path) importArgs;
in
if srcType == "nixpkgs" then
fetchImportChannel srcArgs
else if srcType == "git" then
fetchImportGit (fromJSON srcArgs)
else if srcType == "path" then
importPath srcArgs
else
throw ("Invalid package set source specification: ${srcType} (${srcArgs})")