nix/doc/manual/source/release-notes/rl-2.20.md

Release 2.20.0 (2024-01-29)

• Option allowed-uris can now match whole schemes in URIs without slashes #9547

  If a scheme, such as github: is specified in the allowed-uris option, all URIs starting with github: are allowed. Previously this only worked for schemes whose URIs used the :// syntax.

• Include cgroup stats when building through the daemon #9598

  Nix now also reports cgroup statistics when building through the Nix daemon and when doing remote builds using ssh-ng, if both sides of the connection are using Nix 2.20 or newer.

• Disallow empty search regex in nix search #9481

  nix search now requires a search regex to be passed. To show all packages, use ^.

• Add new eval-system setting #4093

  Add a new eval-system option. Unlike system, it just overrides the value of builtins.currentSystem. This is more useful than overriding system, because you can build these derivations on remote builders which can work on the given system. In contrast, system also affects scheduling which will cause Nix to build those derivations locally even if that doesn't make sense.

  eval-system only takes effect if it is non-empty. If empty (the default) system is used as before, so there is no breakage.

• Import-from-derivation builds the derivation in the build store #9661

  When using --eval-store, importing from a derivation will now result in the derivation being built on the build store, i.e. the store specified in the store Nix option.

  Because the resulting Nix expression must be copied back to the evaluation store in order to be imported, this requires the evaluation store to trust the build store's signatures.

• Mounted SSH Store #7890 #7912

  Introduced the store mounted-ssh-ng://. This store allows full access to a Nix store on a remote machine and additionally requires that the store be mounted in the local filesystem.

• Rename nix show-config to nix config show #7672 #9477

  nix show-config was renamed to nix config show, and nix doctor was renamed to nix config check, to be more consistent with the rest of the command line interface.

• Add command nix hash convert #9452

  This replaces the old nix hash to-* commands, which are still available but will emit a deprecation warning. Please convert as follows:

  • nix hash to-base16 $hash1 $hash2: Use nix hash convert --to base16 $hash1 $hash2 instead.
  • nix hash to-base32 $hash1 $hash2: Use nix hash convert --to nix32 $hash1 $hash2 instead.
  • nix hash to-base64 $hash1 $hash2: Use nix hash convert --to base64 $hash1 $hash2 instead.
  • nix hash to-sri $hash1 $hash2: : Use nix hash convert --to sri $hash1 $hash2 or even just nix hash convert $hash1 $hash2 instead.

• Rename hash format base32 to nix32 #9452

  Hash format base32 was renamed to nix32 since it used a special Nix-specific character set for Base32.

• nix profile now allows referring to elements by human-readable names #8678

  nix profile now uses names to refer to installed packages when running list, remove or upgrade as opposed to indices. Profile element names are generated when a package is installed and remain the same until the package is removed.

  Warning: The manifest.nix file used to record the contents of profiles has changed. Nix will automatically upgrade profiles to the new version when you modify the profile. After that, the profile can no longer be used by older versions of Nix.

• Give nix store add a --hash-algo flag #9809

  Adds a missing feature that was present in the old CLI, and matches our plans to have similar flags for nix hash convert and nix hash path.

• Coercion errors include the failing value

  The error: cannot coerce a <TYPE> to a string message now includes the value which caused the error.

  Before:

  error: cannot coerce a set to a string
  

  After:

  error: cannot coerce a set to a string: { aesSupport = «thunk»;
    avx2Support = «thunk»; avx512Support = «thunk»; avxSupport = «thunk»;
    canExecute = «thunk»; config = «thunk»; darwinArch = «thunk»; darwinMinVersion
    = «thunk»; darwinMinVersionVariable = «thunk»; darwinPlatform = «thunk»; «84
    attributes elided»}
  

• Type errors include the failing value

  In errors like value is an integer while a list was expected, the message now includes the failing value.

  Before:

  error: value is a set while a string was expected
  

  After:

  error: expected a string but found a set: { ghc810 = «thunk»;
    ghc8102Binary = «thunk»; ghc8107 = «thunk»; ghc8107Binary = «thunk»;
    ghc865Binary = «thunk»; ghc90 = «thunk»; ghc902 = «thunk»; ghc92 = «thunk»;
    ghc924Binary = «thunk»; ghc925 = «thunk»;  «17 attributes elided»}
  

• Source locations are printed more consistently in errors #561 #9555

  Source location information is now included in error messages more consistently. Given this code:

  let
    attr = {foo = "bar";};
    key = {};
  in
    attr.${key}
  

  Previously, Nix would show this unhelpful message when attempting to evaluate it:

  error:
         … while evaluating an attribute name
  
         error: value is a set while a string was expected
  

  Now, the error message displays where the problematic value was found:

  error:
         … while evaluating an attribute name
  
           at bad.nix:4:11:
  
              3|   key = {};
              4| in attr.${key}
               |           ^
              5|
  
         error: expected a string but found a set
  

• Some stack overflow segfaults are fixed #9616 #9617

  The number of nested function calls has been restricted, to detect and report infinite function call recursions. The default maximum call depth is 10,000 and can be set with the max-call-depth option.

  This replaces the stack overflow (possible infinite recursion) message.

• Better error reporting for with expressions #9658

  with expressions using non-attrset values to resolve variables are now reported with proper positions, e.g.

  nix-repl> with 1; a
  error:
         … while evaluating the first subexpression of a with expression
           at «string»:1:1:
              1| with 1; a
               | ^
  
         error: expected a set but found an integer
  

• Functions are printed with more detail #7145 #9606

  nix repl, nix eval, builtins.trace, and most other places values are printed will now include function names and source location information:

  $ nix repl nixpkgs
  nix-repl> builtins.map
  «primop map»
  
  nix-repl> builtins.map lib.id
  «partially applied primop map»
  
  nix-repl> builtins.trace lib.id "my-value"
  trace: «lambda id @ /nix/store/8rrzq23h2zq7sv5l2vhw44kls5w0f654-source/lib/trivial.nix:26:5»
  "my-value"
  

• Flake operations like nix develop will no longer fail when run in a Git repository where the flake.lock file is .gitignored #8854 #9324

• Nix commands will now respect Ctrl-C #7145 #6995 #9687

  Previously, many Nix commands would hang indefinitely if Ctrl-C was pressed while performing various operations (including nix develop, nix flake update, and so on). With several fixes to Nix's signal handlers, Nix commands will now exit quickly after Ctrl-C is pressed.

• nix copy to a ssh-ng store now needs --substitute-on-destination (a.k.a. -s) in order to substitute paths on the remote store instead of copying them. The behavior is consistent with nix copy to a different kind of remote store. Previously this behavior was controlled by the builders-use-substitutes setting and --substitute-on-destination was ignored.