Merge pull request cachix#3 from hercules-ci/cabal-fmt

Get cabal-fmt to work

Author: domenkozar

nix/default.nix

@@ -1,12 +1,28 @@
 { sources ? import ./sources.nix }:
+
 with {
     overlay =
       _: pkgs:
-        {
+        let
+          haskell = import sources."haskell.nix" { inherit pkgs; };
+          pkgPlan =
+            haskell.callCabalProjectToNix {
+              index-state = "2019-08-18T00:00:00Z";
+              src = sources.cabal-fmt;
+            };
+          # Instantiate a package set using the generated file.
+          pkgSet =
+            haskell.mkCabalProjectPkgSet {
+              plan-pkgs = import pkgPlan;
+              pkg-def-extras = [];
+              modules = [];
+            };
+        in {
           inherit (import sources.niv {}) niv;
-          inherit (import sources.ormolu { }) ormolu;
+          inherit (import sources.ormolu {}) ormolu;
           inherit (import sources.canonix {}) canonix;
-          cabal-fmt = null;
+          cabal-fmt =
+            pkgSet.config.hsPkgs.cabal-fmt.components.exes.cabal-fmt;
           packages = pkgs.callPackages ./packages.nix {};
         };
   };

nix/run.nix

@@ -22,7 +22,7 @@ let
   -   id: cabal-fmt
       name: cabal-fmt
       description: Format Cabal files
-      entry: cabal-fmt --inplace
+      entry: ${tools.cabal-fmt}/bin/cabal-fmt --inplace
       language: system
       files: '\.cabal$'
   -   id: canonix

nix/sources.json

@@ -23,6 +23,18 @@
         "url": "https://github.com/hercules-ci/canonix/archive/2600422b204b5795fc1f8992d253fedca4d10ea8.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
+    "haskell.nix": {
+        "branch": "master",
+        "description": "Alternative Haskell Infrastructure for Nixpkgs",
+        "homepage": "https://input-output-hk.github.io/haskell.nix",
+        "owner": "input-output-hk",
+        "repo": "haskell.nix",
+        "rev": "2c161d73b51f4c26adb95bd58a63e6e463bcba1c",
+        "sha256": "18apq45lfnn1sgsccn0vi0dnq29zzzvi3naakd8xzdsfn0xp61g9",
+        "type": "tarball",
+        "url": "https://github.com/input-output-hk/haskell.nix/archive/2c161d73b51f4c26adb95bd58a63e6e463bcba1c.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
     "niv": {
         "branch": "master",
         "description": "Easy dependency management for Nix projects",
@@ -35,14 +47,15 @@
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs": {
-        "branch": "nixos-18.09",
+        "branch": "nixos-19.03",
         "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
         "homepage": "https://github.com/NixOS/nixpkgs",
         "owner": "NixOS",
         "repo": "nixpkgs-channels",
-        "rev": "a7e559a5504572008567383c3dc8e142fa7a8633",
-        "sha256": "16j95q58kkc69lfgpjkj76gw5sx8rcxwi3civm0mlfaxxyw9gzp6",
-        "url": "https://github.com/NixOS/nixpkgs-channels/archive/a7e559a5504572008567383c3dc8e142fa7a8633.tar.gz",
+        "rev": "67135fbcc5d5d28390c127ef519b09a362ef2466",
+        "sha256": "00591607zmn1hfjs4959ksh164b0gjqwkvbrc4anx6da8xmhfcc2",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs-channels/archive/67135fbcc5d5d28390c127ef519b09a362ef2466.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "ormolu": {