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refactor(build-image): Extract package set loading into helper

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Some upcoming changes might require the Nix build to be split into
multiple separate nix-build invocations of different expressions, thus
splitting this out is useful.

It also fixes an issue where `build-image/default.nix` might be called
in an environment where no Nix channels are configured.
This commit is contained in:
Vincent Ambo 2019-08-13 23:03:16 +01:00 • committed by Vincent Ambo
parent 3939722063
commit d9168e3e4d
4 changed files with 87 additions and 65 deletions
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64
tools/nixery/build-image/build-image.nix
View file

@ -18,9 +18,11 @@
# registry API.
{
# Package set to used (this will usually be loaded by load-pkgs.nix)
pkgs,
# Image Name
name,
# Image tag, the Nix's output hash will be used if null
# Image tag, the Nix output's hash will be used if null
tag ? null,
# Tool used to determine layer grouping
groupLayers,
@ -36,71 +38,13 @@
# the default here is set to something a little less than that.
maxLayers ? 96,
# Configuration for which package set to use when building.
#
# Both channels of the public nixpkgs repository as well as imports
# from private repositories are supported.
#
# This setting can be invoked with three different formats:
#
# 1. nixpkgs!$channel (e.g. nixpkgs!nixos-19.03)
# 2. git!$repo!$rev (e.g. git!git@github.com:NixOS/nixpkgs.git!master)
# 3. path!$path (e.g. path!/var/local/nixpkgs)
#
# '!' was chosen as the separator because `builtins.split` does not
# support regex escapes and there are few other candidates. It
# doesn't matter much because this is invoked by the server.
pkgSource ? "nixpkgs!nixos-19.03",
...
}:
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-channels/archive/${channel}.tar.gz";
in import (fetchTarball url) {};
# 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 = url: rev:
let
# builtins.fetchGit needs to know whether 'rev' is a reference
# (e.g. a branch/tag) or a revision (i.e. a commit hash)
#
# Since this data is being extrapolated from the supplied image
# tag, we have to guess if we want to avoid specifying a format.
#
# There are some additional caveats around whether the default
# branch contains the specified revision, which need to be
# explained to users.
spec = if (stringLength rev) == 40 then {
inherit url rev;
} else {
inherit url;
ref = rev;
};
in import (fetchGit spec) {};
importPath = path: import (toPath path) {};
source = split "!" pkgSource;
sourceType = elemAt source 0;
pkgs =
if sourceType == "nixpkgs"
then fetchImportChannel (elemAt source 2)
else if sourceType == "git"
then fetchImportGit (elemAt source 2) (elemAt source 4)
else if sourceType == "path"
then importPath (elemAt source 2)
else throw("Invalid package set source specification: ${pkgSource}");
in
# Since this is essentially a re-wrapping of some of the functionality that is
# implemented in the dockerTools, we need all of its components in our top-level
# namespace.
with builtins;
with pkgs;
with dockerTools;