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transposition: Improve perInput error message

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This commit is contained in:
Robert Hensing 2024-01-11 12:16:42 +01:00
parent 7de0c651b7
commit ac5d0b2d4d
1 changed files with 45 additions and 3 deletions
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48
modules/transposition.nix
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@ -7,6 +7,9 @@ let
mkOption
types
;
inherit (lib.strings)
escapeNixIdentifier
;
transpositionModule = {
options = {
@ -24,6 +27,45 @@ let
};
};
perInputAttributeError = { flake, attrName, system, attrConfig }:
# This uses flake.outPath for lack of a better identifier.
# Consider adding a perInput variation that has a normally-redundant argument for the input name.
# Tested manually with
# perSystem = { inputs', ... }: {
# packages.extra = inputs'.nixpkgs.extra;
# packages.default = inputs'.nixpkgs.packages.default;
# packages.veryWrong = (top.config.perInput "x86_64-linux" inputs'.nixpkgs.legacyPackages.hello).packages.default;
# };
# transposition.extra = {};
let
attrPath = "${escapeNixIdentifier attrName}.${escapeNixIdentifier system}";
flakeIdentifier =
if flake._type or null != "flake"
then
throw "An attempt was made to access attribute ${attrPath} on a value that's supposed to be a flake, but may not be a proper flake."
else
builtins.addErrorContext "while trying to find out how to describe what is supposedly a flake, whose attribute ${attrPath} was accessed but does not exist" (
toString flake.outPath
);
# This ought to be generalized by extending attrConfig, but this is the only known and common mistake for now.
alternateAttrNameHint =
if attrName == "packages" && flake?legacyPackages
then # Unfortunately we can't just switch them out, because that will put packages *sets* where single packages are expected in user code, resulting in potentially much worse and more confusing errors down the line.
"\nIt does define legacyPackages; try that instead?"
else "";
in
if flake?${attrName}
then
throw ''
Attempt to access ${attrPath} of flake ${flakeIdentifier}, but it does not have it.
It does have attribute ${escapeNixIdentifier attrName}, so it appears that it does not support system type ${escapeNixIdentifier system}.
''
else
throw ''
Attempt to access ${attrPath} of flake ${flakeIdentifier}, but it does not have attribute ${escapeNixIdentifier attrName}.${alternateAttrNameHint}
'';
in
{
options = {
@ -68,9 +110,9 @@ in
system: flake:
mapAttrs
(attrName: attrConfig:
flake.${attrName}.${system} or (throw ''
Attemt to access non existent attribute ${attrName}.${system} of flake ${flake}.
'')
flake.${attrName}.${system} or (
throw (perInputAttributeError { inherit system flake attrName attrConfig; })
)
)
config.transposition;