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Add the ability to pass lib overlays to mkFlake

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This commit is contained in:
Chris Hodapp 2023-01-28 12:57:54 -08:00
parent 7c7a8bce3d
commit 687dc064a5
1 changed files with 62 additions and 1 deletions
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63
lib.nix
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@ -85,7 +85,66 @@ let
arguments as `inputs` like above.
'';
# Use a list of lib overlays to extend a lib
mkExtendedLib = (
let libExtend = lib: lib.extend;
in overlays: lib: builtins.foldl' libExtend lib overlays
);
# The overlays we are passed could be any of:
#
# (1) A simple attribute attribute set
# (2) A function from `prev` to an attribute set
# (3) A function from `final` and `prev` to an attribute set
# (4) A function from `inputs`, `final`, `prev`, to an attribute set
# (5) A path or string pointing at a file containing any of (1) - (4)
#
# We seek to normalize these possibilities so that we always have a function
# from `final` and `prev` to an attribute set, which is suitable for use with
# mkExtendedLib. This may mean specializing on the `inputs` that we are passed.
#
toStandardOverlay = inputs: freeformOverlay: (
let
reifiedFreeformOverlay = (
if (builtins.isPath freeformOverlay) || (builtins.isString freeformOverlay)
then import freeformOverlay
else freeformOverlay
);
in (final: prev:
# apply the correct number of arguments to `reifiedFreeformOverlay`. Of note
# is the fact that the bindings that pass too many args should not blow up
# because laziness and short-circuiting should ensure that they are never
# actually invoked.
let
noArg = reifiedFreeformOverlay;
oneArg = reifiedFreeformOverlay prev;
twoArg = reifiedFreeformOverlay final prev;
threeArg = reifiedFreeformOverlay inputs final prev;
in
if ! builtins.isFunction noArg then noArg
else if ! builtins.isFunction oneArg then oneArg
else if ! builtins.isFunction twoArg then twoArg
else if ! builtins.isFunction threeArg then threeArg
else throw ''
Received a lib overlay that takes the wrong number of args. Please ensure
that your lib overlay function takes some suffix of this potential argument
list: `inputs`, `final`, `prev`
''
)
);
# Convert a list or attribute set of freeform overlays to a list of standard
# overlays, suitable for use with `mkExtendedLib`
getOverlayList = inputOverlays: (
if builtins.isList inputOverlays
then inputs: builtins.map (toStandardOverlay inputs) inputOverlays
else getOverlayList (builtins.attrValues inputOverlays)
);
flake-parts-lib = {
inherit mkExtendedLib;
evalFlakeModule =
args@
{ inputs ? self.inputs
@ -98,6 +157,7 @@ let
${errorExample}
'')
, libOverlays ? [ ]
}:
throwIf
(!args?self && !args?inputs) ''
@ -115,7 +175,8 @@ let
''
(module:
lib.evalModules {
let fullLib = mkExtendedLib (getOverlayList libOverlays inputs) lib;
in fullLib.evalModules {
specialArgs = {
inherit self flake-parts-lib;
inputs = args.inputs or /* legacy, warned above */ self.inputs;