all the pieces

Author: alicebob

.gitignore

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+result
+gohello

Makefile

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+.PHONY: build
+build:
+	go build
+
+.PHONY: nix
+nix:
+	nix-build -A gohello
+
+.PHONY: shell
+shell:
+	nix-shell
+
+.PHONY: nixpin
+nixpin:
+	#nix-shell -p npins --run "npins init"
+	nix-shell --run "npins update"
+
+.PHONY: nixfmt
+nixfmt:
+	nix-shell --run "nixfmt *.nix"
+

README.md

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+Tiny Go program to test some build infrastructure. Uses Nix with npins for the build setup.

default.nix

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+let
+  sources = import ./npins/default.nix;
+  pkgs = import sources.nixpkgs { };
+in
+{
+  gohello = pkgs.buildGoModule {
+    name = "gohello";
+    # buildInputs = [ gocache ];
+    src = pkgs.lib.sourceByRegex ./. [
+      "go.(mod|sum)"
+      ".*\.go"
+    ];
+    vendorHash = null; # uses ./vendor/
+    doCheck = false;
+  };
+
+  shell = pkgs.mkShellNoCC {
+    packages = [
+      pkgs.nixfmt-rfc-style
+      pkgs.npins
+    ];
+  };
+}

go.mod

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+module github.com/alicebob/gohello
+
+go 1.22.0

main.go

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+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	fmt.Printf("Hello %s!\n", os.Getenv("USER"))
+}

npins/default.nix

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+# Generated by npins. Do not modify; will be overwritten regularly
+let
+  data = builtins.fromJSON (builtins.readFile ./sources.json);
+  version = data.version;
+
+  mkSource = spec:
+    assert spec ? type; let
+      path =
+        if spec.type == "Git" then mkGitSource spec
+        else if spec.type == "GitRelease" then mkGitSource spec
+        else if spec.type == "PyPi" then mkPyPiSource spec
+        else if spec.type == "Channel" then mkChannelSource spec
+        else builtins.throw "Unknown source type ${spec.type}";
+    in
+    spec // { outPath = path; };
+
+  mkGitSource = { repository, revision, url ? null, hash, ... }:
+    assert repository ? type;
+    # At the moment, either it is a plain git repository (which has an url), or it is a GitHub/GitLab repository
+    # In the latter case, there we will always be an url to the tarball
+    if url != null then
+      (builtins.fetchTarball {
+        inherit url;
+        sha256 = hash; # FIXME: check nix version & use SRI hashes
+      })
+    else assert repository.type == "Git"; builtins.fetchGit {
+      url = repository.url;
+      rev = revision;
+      # hash = hash;
+    };
+
+  mkPyPiSource = { url, hash, ... }:
+    builtins.fetchurl {
+      inherit url;
+      sha256 = hash;
+    };
+
+  mkChannelSource = { url, hash, ... }:
+    builtins.fetchTarball {
+      inherit url;
+      sha256 = hash;
+    };
+in
+if version == 3 then
+  builtins.mapAttrs (_: mkSource) data.pins
+else
+  throw "Unsupported format version ${toString version} in sources.json. Try running `npins upgrade`"

npins/sources.json

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+{
+  "pins": {
+    "nixpkgs": {
+      "type": "Channel",
+      "name": "nixos-24.05",
+      "url": "https://releases.nixos.org/nixos/24.05/nixos-24.05.556.fafeae3d248c/nixexprs.tar.xz",
+      "hash": "1r06n8gq6ikm89svq95lq6s3p4aiv625wl46ncfdgv804p1fc9zs"
+    }
+  },
+  "version": 3
+}

shell.nix

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+(import ./.).shell