nix/doc/manual/source/release-notes/rl-2.2.md

Release 2.2 (2019-01-11)

This is primarily a bug fix release. It also has the following changes:

• In derivations that use structured attributes (i.e. that specify set the __structuredAttrs attribute to true to cause all attributes to be passed to the builder in JSON format), you can now specify closure checks per output, e.g.:

  outputChecks."out" = {
    # The closure of 'out' must not be larger than 256 MiB.
    maxClosureSize = 256 * 1024 * 1024;
  
    # It must not refer to C compiler or to the 'dev' output.
    disallowedRequisites = [ stdenv.cc "dev" ];
  };
  
  outputChecks."dev" = {
    # The 'dev' output must not be larger than 128 KiB.
    maxSize = 128 * 1024;
  };
  

• The derivation attribute requiredSystemFeatures is now enforced for local builds, and not just to route builds to remote builders. The supported features of a machine can be specified through the configuration setting system-features.

  By default, system-features includes kvm if /dev/kvm exists. For compatibility, it also includes the pseudo-features nixos-test, benchmark and big-parallel which are used by Nixpkgs to route builds to particular Hydra build machines.

• Sandbox builds are now enabled by default on Linux.

• The new command nix doctor shows potential issues with your Nix installation.

• The fetchGit builtin function now uses a caching scheme that puts different remote repositories in distinct local repositories, rather than a single shared repository. This may require more disk space but is faster.

• The dirOf builtin function now works on relative paths.

• Nix now supports SRI hashes, allowing the hash algorithm and hash to be specified in a single string. For example, you can write:

  import <nix/fetchurl.nix> {
    url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
    hash = "sha256-XSLa0FjVyADWWhFfkZ2iKTjFDda6mMXjoYMXLRSYQKQ=";
  };
  

  instead of

  import <nix/fetchurl.nix> {
    url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
    sha256 = "5d22dad058d5c800d65a115f919da22938c50dd6ba98c5e3a183172d149840a4";
  };
  

  In fixed-output derivations, the outputHashAlgo attribute is no longer mandatory if outputHash specifies the hash.

  nix hash-file and nix hash-path now print hashes in SRI format by default. They also use SHA-256 by default instead of SHA-512 because that's what we use most of the time in Nixpkgs.

• Integers are now 64 bits on all platforms.

• The evaluator now prints profiling statistics (enabled via the NIX_SHOW_STATS and NIX_COUNT_CALLS environment variables) in JSON format.

• The option --xml in nix-store --query has been removed. Instead, there now is an option --graphml to output the dependency graph in GraphML format.

• All nix-* commands are now symlinks to nix. This saves a bit of disk space.

• nix repl now uses libeditline or libreadline.