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top-level: Document why nixpkgsFun doesn't close over inferred default arguments

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John Ericson 2016-11-26 15:34:13 -08:00 committed by John Ericson
parent 05c12f147e
commit a55d1ecc90
1 changed files with 9 additions and 2 deletions
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pkgs/top-level/default.nix
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@ -55,8 +55,15 @@ in let
# whatever arguments it doesn't explicitly provide. This way,
# `all-packages.nix` doesn't know more than it needs too.
#
# It's OK that `args` doesn't include the defaults: they'll be
# deterministically inferred the same way.
# It's OK that `args` doesn't include default arguemtns from this file:
# they'll be deterministically inferred. In fact we must *not* include them,
# because it's important that if some parameter which affects the default is
# substituted with a different argument, the default is re-inferred.
#
# To put this in concrete terms, this function is basically just used today to
# use package for a different platform for the current platform (namely cross
# compiling toolchains and 32-bit packages on x86_64). In both those cases we
# want the provided non-native `system` argument to affect the stdenv chosen.
nixpkgsFun = newArgs: import ./. (args // newArgs);
# Partially apply some arguments for building bootstraping stage pkgs