Question about dependency on "which"

[Lysxia]

I'm trying to build neuron using plain cabal, instead of via Nix as documented, so I could be missing something. There are a few hacks needed on the way to reproduce the following problem, but basically, if I run cabal install neuron, I get the error that neuron-search could not be found while compiling neuron/src/app/Neuron/CLI/Search.hs.

In neuron/src/app/Neuron/CLI/Search.hs, the function staticWhich from the package "which" is used to find the path to the bash script neuron-search.

neuron/neuron/src/app/Neuron/CLI/Search.hs

Line 20 in 7d57e45

neuronSearchScript = $(staticWhich "neuron-search")

I could make it compile using the Paths_neuron module instead, but I'm not sure whether that would work for Nix. Does this look like an acceptable fix?

neuronSearchScript = $(TH.lift (unsafePerformIO (getDataFileName "src-bash/neuron-search")))

Lysxia@51e5eb0#diff-156fa4df5d0d36eccfe427a54b100371R22

(Note: I'm actually using tag 0.6.0.0 instead of master, to avoid rib-core, but the relevant line of code hasn't changed so the issue still seems current.)

[srid]

May I know the reason for trying to build it with plain cabal, outside of Nix?

Generally speaking, this is best done in the which library. There is a PR open for that, but I don't know the status of it: obsidiansystems/which#3

[Lysxia]

I don't want to install and learn to use yet another package manager. The required changes to build with vanilla cabal are quite minor; I can volunteer to patch and maintain anything that has to do with this, but I would also understand if you just don't want the extra overhead; this issue is the only one I'm not sure how to fix without breaking stuff.

The linked patch to which doesn't seem it would actually work if the required executable is a data file of the current package, because it depends on that executable being on PATH before the package is built.

[srid]

Since this is the only place where staticWhich is used (it used to be used in several places), then I suppose we can just get rid of it entirely, and possibly even embed the neuron-search script in haskell (via Text.RawString.QQ).

I don't particularly like seeing unsafePerformIO here (doesn't seem like a conventional solution; is that what all these TH libraries do?).

In any case, whatever change we make should continue to work in nix-build (./result/bin/neuron -d ./guide search should not fail), and should not break the compilation in the bin/run and bin/test scripts (which use ghcid).

[srid]

Plus, it should not revert the nix install size optimizations done in #193 (comment) (do a nix install on a fresh Ubuntu VM, and check the size of /nix). I vaguely remember seeing an issue with cabal's Paths_neuron adding unnecessary dependencies.

[Lysxia]

I don't particularly like seeing unsafePerformIO here (doesn't seem like a conventional solution; is that what all these TH libraries do?).

The conventional solution is to use runIO, I didn't remember the name off-hand.

[Lysxia]

Awesome!

[srid]

Had to revert that. If you're interested, please see #432

Enough dealing with non-nix requests for me today.