buildGoPackage: include goDeps in nix-shell GOPATH

[kamilchm]

Motivation for this change

nix-shell should works as development environment for Go packages
see https://gist.github.com/qknight/ec772db7ab484296c64af008de628d9e

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • OS X
  • Linux
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

[mention-bot]

By analyzing the blame information on this pull request, we identified @wkennington, @ehmry and @lethalman to be potential reviewers

[chris-martin]

I'm looking at the difference between this as #15490 and I don't understand the change. I didn't need the shell hook to add the dependencies to the GOPATH when I tried this before. I suspect they end up on the path twice now?

[kamilchm]

I tested you version and it didn't create any link to dependencies sources when used with current master. This one worked and build proper GOPATH with all needed sources for me.

[qknight]

i've been playing with this and for some dependencies it seems to work! if i want to use a lib which is not already listed in ../../libs.json in nixpkgs i don't see how to support that with this patch.

example1

i noticed this:

• without having "include": "../../libs.json", in the deps.json, no error will appear, it just won't find any dependencies listed in deps.json later on. i would like to see an error here.

• using "include": "../../libs.json",, in the deps.json, makes it find golang.org/x/net

• using "include": "../../../libs.json", makes it fail with:

  error: opening file ‘/home/joachim/Desktop/projects/nixos/nixpkgs/pkgs/development/libs.json’: No such file or directory
  

example2

it seems to ignore some dependencies from deps.json file, which is located in the project directory.

[
  {
    "include": "../../libs.json",
    "packages": [
      "golang.org/x/net",
      "asdofoasidioasdfiogolang.org/x/net/webfoo"
    ]
  }
]

beucase there is never a failure for the above dependency asdofoasidioasdfiogolang.org/x/net/webfoo.

request

• please show me how to use my own custom libs.json and deps.json extensions, which might be in the project directory where i run nix-shell from.
• there should be an error message when a dependency listed in packages is not in the nixpkgs's global libs.json

[kamilchm]

@qknight I'm looking at nix code to see if I can generate and parse nix expressions easily from Go to replace JSON in go2nix, as it was mentioned few times as a better overall solution. I'll come back to nix-shell and Go package development after few more experiments, holding your request for now.

[mstone]

@kamilchm @chris-martin @qknight -- this change works well for me on a recent nixpkgs checkout and fixes a regression introduced by #16017.

Can we merge it, or is there additional required testing, documentation, or development work?

[Mic92]

This code is already included: https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/go-modules/generic/default.nix#L183