Can generate broken filepaths for local directories

[Fuuzetsu]

if we cabal2nix over a local directory such as foo-1.2.3 which is a common naming scheme from cabal unpack, the path is inserted verbatim and nix complains about a parse error.

The local paths should just be always quoted. I imagine problems in cases the filepath itself has quotes &c but that's a much more rare scenario.

cc @bennofs

[bennofs]

Putting quotes arround the src directory changes behaviour. Right now, the src directory is copied to the store and then the store path is set to $src for the builder. If we quote the path, then $src will be directly the relative path, which means that for example chroot builds will fail. Correct me if I'm wrong about this.

[Fuuzetsu]

Wouldn't that mean that it's impossible to do chroot builds for such paths because we have to quote them?

[bennofs]

I just found out that we don't need to quote them. ./foo-1.2.3 is also parsed fine as a path by nix. However, since b217210538e51c79d222fd71e82e374edce0dec9, cabal2nix should automatically do that. I just tested:

$ cabal get lens-4.4
$ cabal2nix lens-4.4
# This file was auto-generated by cabal2nix. Please do NOT edit manually!

{ cabal, bifunctors, comonad, contravariant, deepseq, distributive
, doctest, exceptions, filepath, free, genericDeriving, hashable
, hlint, HUnit, mtl, nats, parallel, primitive, profunctors
, QuickCheck, reflection, semigroupoids, semigroups, simpleReflect
, split, tagged, testFramework, testFrameworkHunit
, testFrameworkQuickcheck2, testFrameworkTh, text, transformers
, transformersCompat, unorderedContainers, vector, void, zlib
}:

cabal.mkDerivation (self: {
  pname = "lens";
  version = "4.4";
  src = ./lens-4.4;
  buildDepends = [
    bifunctors comonad contravariant distributive exceptions filepath
    free hashable mtl parallel primitive profunctors reflection
    semigroupoids semigroups split tagged text transformers
    transformersCompat unorderedContainers vector void zlib
  ];
  testDepends = [
    deepseq doctest filepath genericDeriving hlint HUnit mtl nats
    parallel QuickCheck semigroups simpleReflect split testFramework
    testFrameworkHunit testFrameworkQuickcheck2 testFrameworkTh text
    transformers unorderedContainers vector
  ];
  meta = {
    homepage = "http://github.com/ekmett/lens/";
    description = "Lenses, Folds and Traversals";
    license = self.stdenv.lib.licenses.bsd3;
    platforms = self.ghc.meta.platforms;
  };
})

[Fuuzetsu]

This only works for paths that start at . so it would still be broken for a case such as cabal2nix /some/location/lens-4.4: src = ./some/location/lens-4.4 doesn't make sense here.

[bennofs]

cabal2nix only prepends ./ if the path doesn't already contain a slash. So /some/location/lens-4.4 is unchanged. Nix requires that paths contain a slash.

[Fuuzetsu]

OK, so the problem still exists, right? Just making sure we're on the same track.

[bennofs]

No, it's fixed since b217210.

[Fuuzetsu]

How exactly is this fixed? See

[shana@lenalee:~/programming]$ cd /tmp

[shana@lenalee:/tmp]$ nix-shell -p pkgs.haskellPackages_ghc783.cabalInstall -p pkgs.haskellPackages_ghc783.ghc

[nix-shell:/tmp]$ cabal unpack lens
Downloading lens-4.4.0.1...
Unpacking to lens-4.4.0.1/

[nix-shell:/tmp]$ exit

[shana@lenalee:/tmp]$ nix-shell -p pkgs.myHaskellPackages_ghc783.cabal2nix -p pkgs.myHaskellPackages_ghc783.ghc

[nix-shell:/tmp]$ cabal2nix /tmp/lens-4.4.0.1/
# This file was auto-generated by cabal2nix. Please do NOT edit manually!

{ cabal, bifunctors, comonad, contravariant, deepseq, distributive
, doctest, exceptions, filepath, free, genericDeriving, hashable
, hlint, HUnit, mtl, nats, parallel, primitive, profunctors
, QuickCheck, reflection, semigroupoids, semigroups, simpleReflect
, split, tagged, testFramework, testFrameworkHunit
, testFrameworkQuickcheck2, testFrameworkTh, text, transformers
, transformersCompat, unorderedContainers, vector, void, zlib
}:

cabal.mkDerivation (self: {
  pname = "lens";
  version = "4.4.0.1";
  src = /tmp/lens-4.4.0.1/;
  buildDepends = [
    bifunctors comonad contravariant distributive exceptions filepath
    free hashable mtl parallel primitive profunctors reflection
    semigroupoids semigroups split tagged text transformers
    transformersCompat unorderedContainers vector void zlib
  ];
  testDepends = [
    deepseq doctest filepath genericDeriving hlint HUnit mtl nats
    parallel QuickCheck semigroups simpleReflect split testFramework
    testFrameworkHunit testFrameworkQuickcheck2 testFrameworkTh text
    transformers unorderedContainers vector
  ];
  meta = {
    homepage = "http://github.com/ekmett/lens/";
    description = "Lenses, Folds and Traversals";
    license = self.stdenv.lib.licenses.bsd3;
    platforms = self.ghc.meta.platforms;
  };
})

[nix-shell:/tmp]$ cabal2nix /tmp/lens-4.4.0.1/ > default.nix

[nix-shell:/tmp]$ nix-shell default.nix
error: syntax error, unexpected ';', at /tmp/default.nix:15:27

This is with cabal2nix HEAD. No matter how I look at it, it generates a path nix can't parse.

[bennofs]

Ah, I think the problem isn't the -, but the trailing slash.

[Fuuzetsu]

Yep, confirmed it with a path without - or ..