"'allow-import-from-derivation' is disabled" error

[kamoii]

I'm new to nix, so I don't know if this is an error or intended, but when I try to run nix flake show,
I get the error 'allow-import-from-derivation' is disabled.

$ nix flake show --version
nix (Nix) 2.4
$ nix flake show --show-trace
git+file:///.../github/purenix?ref=main&rev=4dd6ec3913825a66cc2c8a82219428d812c0a203
├───defaultPackage
error: cannot build '/nix/store/vnvd0kq9vphs2b191yh0wk1z7ffffjlq-cabal2nix-purenix.drv' during evaluation because the option 'allow-import-from-derivation' is disabled

       … while importing '/nix/store/ybyh4wwhkwg6fpp2acqd87rkrhj4499r-cabal2nix-purenix'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:87:47:

           86|       # info that callPackage uses to determine the arguments).
           87|       drv = if lib.isFunction fn then fn else import fn;
             |                                               ^
           88|       auto = builtins.intersectAttrs (lib.functionArgs drv) scope;

       … while evaluating 'drvScope'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:91:18:

           90|       # this wraps the `drv` function to add a `overrideScope` function to the result.
           91|       drvScope = allArgs: drv allArgs // {
             |                  ^
           92|         overrideScope = f:

       … from call site

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/lib/customisation.nix:69:16:

           68|     let
           69|       result = f origArgs;
             |                ^
           70|

       … while evaluating 'makeOverridable'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/lib/customisation.nix:67:24:

           66|   */
           67|   makeOverridable = f: origArgs:
             |                        ^
           68|     let

       … from call site

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:101:8:

          100|       };
          101|     in lib.makeOverridable drvScope (auto // manualArgs);
             |        ^
          102|

       … while evaluating 'callPackageWithScope'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:78:37:

           77|   # here `bar` is a manual argument.
           78|   callPackageWithScope = scope: fn: manualArgs:
             |                                     ^
           79|     let

       … from call site

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:118:28:

          117|   defaultScope = mkScope self;
          118|   callPackage = drv: args: callPackageWithScope defaultScope drv args;
             |                            ^
          119|

       … while evaluating 'callPackage'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:118:22:

          117|   defaultScope = mkScope self;
          118|   callPackage = drv: args: callPackageWithScope defaultScope drv args;
             |                      ^
          119|

       … from call site

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:174:9:

          173|       };
          174|     }) (self.callPackage src args);
             |         ^
          175|

       … while evaluating 'overrideCabal'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/lib/compose.nix:38:22:

           37|    */
           38|   overrideCabal = f: drv: (drv.override (args: args // {
             |                      ^
           39|     mkDerivation = drv: (args.mkDerivation drv).override f;

       … from call site

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:162:5:

          161|   callPackageKeepDeriver = src: args:
          162|     overrideCabal (orig: {
             |     ^
          163|       preConfigure = ''

       … while evaluating 'callPackageKeepDeriver'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:161:33:

          160|   # annoyance.
          161|   callPackageKeepDeriver = src: args:
             |                                 ^
          162|     overrideCabal (orig: {

       … from call site

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:218:14:

          217|            inherit src;
          218|          }) (callPackageKeepDeriver expr args);
             |              ^
          219|

       … while evaluating 'overrideCabal'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/lib/compose.nix:38:22:

           37|    */
           38|   overrideCabal = f: drv: (drv.override (args: args // {
             |                      ^
           39|     mkDerivation = drv: (args.mkDerivation drv).override f;

       … from call site

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:216:10:

          215|         };
          216|       in overrideCabal (orig: {
             |          ^
          217|            inherit src;

       … while evaluating 'callCabal2nixWithOptions'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:205:66:

          204|     # Creates a Haskell package from a source package by calling cabal2nix on the source.
          205|     callCabal2nixWithOptions = name: src: extraCabal2nixOptions: args:
             |                                                                  ^
          206|       let

       … from call site

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:220:38:

          219|
          220|     callCabal2nix = name: src: args: self.callCabal2nixWithOptions name src "" args;
             |                                      ^
          221|

       … while evaluating 'callCabal2nix'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/make-package-set.nix:220:32:

          219|
          220|     callCabal2nix = name: src: args: self.callCabal2nixWithOptions name src "" args;
             |                                ^
          221|

       … from call site

       at /nix/store/lgkd30fbvyz9ndyqai6c2cckbfp12bfc-source/nix/overlay.nix:33:11:

           32|           in
           33|           hfinal.callCabal2nix "purenix" src { };
             |           ^
           34|       };

       … while evaluating the attribute 'haskellPackages.purenix'

       at /nix/store/lgkd30fbvyz9ndyqai6c2cckbfp12bfc-source/nix/overlay.nix:5:9:

            4|       prev.haskell.packageOverrides hfinal hprev // {
            5|         purenix =
             |         ^
            6|           let

       … while evaluating 'overrideCabal'

       at /nix/store/r85b90gdvvpfl04rnn2aisr6jggi2pp0-source/pkgs/development/haskell-modules/lib/compose.nix:38:22:

           37|    */
           38|   overrideCabal = f: drv: (drv.override (args: args // {
             |                      ^
           39|     mkDerivation = drv: (args.mkDerivation drv).override f;

       … from call site

       at /nix/store/lgkd30fbvyz9ndyqai6c2cckbfp12bfc-source/nix/overlay.nix:38:5:

           37|   purenix =
           38|     final.haskell.lib.compose.justStaticExecutables final.haskellPackages.purenix;
             |     ^
           39|

       … while evaluating the attribute 'purenix'

       at /nix/store/lgkd30fbvyz9ndyqai6c2cckbfp12bfc-source/nix/overlay.nix:37:3:

           36|
           37|   purenix =
             |   ^
           38|     final.haskell.lib.compose.justStaticExecutables final.haskellPackages.purenix;

       … while evaluating the attribute 'defaultPackage'

       at /nix/store/lgkd30fbvyz9ndyqai6c2cckbfp12bfc-source/flake.nix:15:11:

           14|         {
           15|           defaultPackage = pkgs.purenix;
             |           ^
           16|           packages.purenix = pkgs.purenix;

[cdepillabout]

Unfortunately this is a problem with IFD in flakes.

There are a couple things on the Nix issue tracker that talk about this, as well as a few posts on Discourse:

• Don't allow IFD in flakes by default NixOS/nix#5253
• nix flake check breaks on IFD in multi-platform flake NixOS/nix#4265
• https://discourse.nixos.org/t/how-to-use-flakes-with-ifd/10300

If you'd like nix flake show working locally, you'll have to make sure to only build for your local system/architecture:

diff --git a/flake.nix b/flake.nix
index a15d0ce..192bdf6 100644
--- a/flake.nix
+++ b/flake.nix
@@ -30,5 +30,5 @@
           };
         };
     in
-    { inherit overlay; } // inputs.flake-utils.lib.eachDefaultSystem perSystem;
+    { inherit overlay; } // inputs.flake-utils.lib.eachSystem [ "x86_64-linux" ]  perSystem;
 }

With this change, nix flake show works again:

$ nix flake show
git+file:///home/me/git/purenix-org/purenix
├───defaultPackage
│   └───x86_64-linux: package 'purenix-1.0'
├───devShell
│   └───x86_64-linux: development environment 'ghc-shell-for-purenix-1.0-0'
├───devShells
│   └───x86_64-linux
│       ├───hacking-on-purenix: development environment 'ghc-shell-for-purenix-1.0-0'
│       └───use-purenix: development environment 'use-purenix-shell'
├───overlay: Nixpkgs overlay
└───packages
    └───x86_64-linux
        └───purenix: package 'purenix-1.0'

Since this is more of an upstream Nix problem, I'll go ahead and close this!

[kamoii]

@cdepillabout
Thank you very much for the information, I did not know about IFD, I will look into it.