diff options
Diffstat (limited to 'doc/manual/src/release-notes/rl-next.md')
| -rw-r--r-- | doc/manual/src/release-notes/rl-next.md | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md index 2ec864ee4..4f3c9ce41 100644 --- a/doc/manual/src/release-notes/rl-next.md +++ b/doc/manual/src/release-notes/rl-next.md @@ -14,3 +14,21 @@ This function is only available if you enable the experimental feature `fetch-closure`. + +* New experimental feature: *impure derivations*. These are + derivations that can produce a different result every time they're + built. Here is an example: + + ```nix + stdenv.mkDerivation { + name = "impure"; + __impure = true; # marks this derivation as impure + buildCommand = "date > $out"; + } + ``` + + Running `nix build` twice on this expression will build the + derivation twice, producing two different content-addressed store + paths. Like fixed-output derivations, impure derivations have access + to the network. Only fixed-output derivations and impure derivations + can depend on an impure derivation. |