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pare down the error message

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Ben Burdette 2020-11-11 11:05:21 -07:00
parent 3edfe6090e
commit 8895fa70a4
1 changed files with 4 additions and 22 deletions
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26
src/libexpr/eval.cc
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@ -1373,31 +1373,13 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
if (j != args.end()) { if (j != args.end()) {
actualArgs->attrs->push_back(*j); actualArgs->attrs->push_back(*j);
} else if (!i.def) { } else if (!i.def) {
throwMissingArgumentError(i.pos, R"(cannot auto-call a function that has an argument without a default value ('%1%') throwMissingArgumentError(i.pos, R"(cannot evaluate a function that has an argument without a value ('%1%')
An 'auto-call' is when a nix expression is evaluated without any external arguments. Nix attempted to evaluate a function as a top level expression; in this case it must have all its
If that nix expression is a function, and that function's arguments all have default arguments supplied either by default values, or passed explicitly with --arg or --argstr.
values, then all is well.
But if the function arguments don't have default values, evaluation fails. https://nixos.org/manual/nix/stable/#ss-functions)", i.name);
The classic case for this error is evaluating a nix file that expects
to be evaluated by callPackage.
# in 'callPackage' format: expression is a function that takes an argument 'stdenv'.
# callPackage would implicitly pull 'stdenv' from nixpkgs, then call this function.
{ stdenv }:
stdenv.mkDerivation {
...
# in 'auto-call' format: nixpkgs is imported explicitly, and used directly.
let
nixpkgs = import <nixpkgs> {};
in
nixpkgs.stdenv.mkDerivation {
...
More about callPackage:
https://nixos.org/guides/nix-pills/callpackage-design-pattern.html)", i.name);
} }
} }
} }