Commits on Jan 24, 2020

1. Give a better error message when a flake path is not a directory

   

   edolstra committed Jan 24, 2020
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2. HandleLockFile -> LockFileMode

   

   edolstra committed Jan 24, 2020
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3. Respect lock files of inputs + fine-grained lock file control …

   When computing a lock file, we now respect the lock files of flake
   inputs. This is important for usability / reproducibility. For
   example, the 'nixops' flake depends on the 'nixops-aws' and
   'nixops-hetzner' repositories. So when the 'nixops' flake is used in
   another flake, we want the versions of 'nixops-aws' and
   'nixops-hetzner' locked by the the 'nixops' flake because those
   presumably have been tested.
   
   This can lead to a proliferation of versions of flakes like 'nixpkgs'
   (since every flake's lock file could depend on a different version of
   'nixpkgs'). This is not a major issue when using Nixpkgs overlays or
   NixOS modules, since then the top-level flake composes those
   overlays/modules into *its* version of Nixpkgs and all other versions
   are ignored. Lock file computation has been made a bit more lazy so it
   won't try to fetch all those versions of 'nixpkgs'.
   
   However, in case it's necessary to minimize flake versions, there now
   are two input attributes that allow this. First, you can copy an input
   from another flake, as follows:
   
     inputs.nixpkgs.follows = "dwarffs/nixpkgs";
   
   This states that the calling flake's 'nixpkgs' input shall be the same
   as the 'nixpkgs' input of the 'dwarffs' input.
   
   Second, you can override inputs of inputs:
   
     inputs.nixpkgs.url = github:edolstra/nixpkgs/<hash>;
     inputs.nixops.inputs.nixpkgs.url = github:edolstra/nixpkgs/<hash>;
   
   or equivalently, using 'follows':
   
     inputs.nixpkgs.url = github:edolstra/nixpkgs/<hash>;
     inputs.nixops.inputs.nixpkgs.follows = "nixpkgs";
   
   This states that the 'nixpkgs' input of the 'nixops' input shall be
   the same as the calling flake's 'nixpkgs' input.
   
   Finally, at '-v' Nix now prints the changes to the lock file, e.g.
   
     $ nix flake update ~/Misc/eelco-configurations/hagbard
     inputs of flake 'git+file:///home/eelco/Misc/eelco-configurations?subdir=hagbard' changed:
       updated 'nixpkgs': 'github:edolstra/nixpkgs/7845bf5f4b3013df1cf036e9c9c3a55a30331db9' -> 'github:edolstra/nixpkgs/03f3def66a104a221aac8b751eeb7075374848fd'
       removed 'nixops'
       removed 'nixops/nixops-aws'
       removed 'nixops/nixops-hetzner'
       removed 'nixops/nixpkgs'

   

   edolstra committed Jan 24, 2020
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