Bootstrapping a new project

[asheshambasta]

Bootstrapping a new project

[Gabriella439]

@asheshambasta: The short answer is that you can fix the problem by running:

$ nix-shell --attr avahi-dbus.env release.nix

The issue here is that running nix-shell directly on the derivation for the Haskell derivation does not behave well (unlike almost all other Nix packages). Instead, every Haskell derivation has an env attribute that you have to use nix-shell on instead. See the beginning of this section for more details:

https://github.com/Gabriel439/haskell-nix/tree/master/project0#building-with-cabal

[asheshambasta]

@Gabriel439 thanks a lot for clarifying this. This indeed fixes the issue.
Is there a more detailed resource on why this is with Haskell packages?

I'm closing this issue since this seems fixed for me.
Apologies for a question-issue.

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Maybe we can add to the readme that if the package name is A, the user has to pass --attr A.env instead of env, which is what seems to have stumped me.

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Interestingly, as per the changes in my minimal repro repo., adding a shell.nix with the given buildInputs seems to work. I'm not entirely sure why that is.

[Gabriella439]

@asheshambasta: There isn't an explanation of why this is the case. That idiom is taken from the Haskell section of the Nixpkgs manual, but it doesn't explain the rationale behind it.

[asheshambasta]

@Gabriel439 Thanks for the link. I'll read it and respond back.

I'm not sure where else to ask, but following: https://github.com/Gabriel439/haskell-nix/blob/master/project2/README.md, I've added the zlib (instead of tar in the README) dependency in the avahi-dbus.nix, but builds still fail with the extra-libraries option in the cabal file.
I've added a commit that demonstrates this: asheshambasta/avahi-dbus@f8a3423

[Gabriella439]

@asheshambasta: I believe you need to depend on zlib.dev instead of zlib. zlib contains just the shared library files, whereas zlib.dev includes the header files, too, which is what cabal is looking for.