Bump nixpkgs and simplify/clean up nix setup (#1529)

* Refactor tests and fix README

* fix linting hints from new hlint version

* postgrest-style with new nixpkgs-fmt

nix/overlays/gitignore.nix

@@ -15,5 +15,6 @@ self: super:
         rev = "2ced4519f865341adcb143c5d668f955a2cb997f";
         sha256 = "sha256:0fc5bgv9syfcblp23y05kkfnpgh3gssz6vn24frs8dzw39algk2z";
       };
-    in (super.callPackage gitignoreSrc {}).gitignoreSource;
+    in
+    (super.callPackage gitignoreSrc { }).gitignoreSource;
 }

nix/overlays/haskell-packages/Cabal.nix

@@ -0,0 +1,90 @@
+{ mkDerivation
+, array
+, base
+, base-compat
+, base-orphans
+, binary
+, bytestring
+, containers
+, deepseq
+, Diff
+, directory
+, filepath
+, integer-logarithms
+, mtl
+, optparse-applicative
+, parsec
+, pretty
+, process
+, QuickCheck
+, stdenv
+, stm
+, tagged
+, tar
+, tasty
+, tasty-golden
+, tasty-hunit
+, tasty-quickcheck
+, temporary
+, text
+, time
+, transformers
+, tree-diff
+, unix
+}:
+mkDerivation {
+  pname = "Cabal";
+  version = "3.0.0.0";
+  sha256 = "5143ec26d740c1a508c93a8860e64407e7546c29b9817db20ff1595c1968d287";
+  setupHaskellDepends = [ mtl parsec ];
+  libraryHaskellDepends = [
+    array
+    base
+    binary
+    bytestring
+    containers
+    deepseq
+    directory
+    filepath
+    mtl
+    parsec
+    pretty
+    process
+    text
+    time
+    transformers
+    unix
+  ];
+  testHaskellDepends = [
+    array
+    base
+    base-compat
+    base-orphans
+    binary
+    bytestring
+    containers
+    deepseq
+    Diff
+    directory
+    filepath
+    integer-logarithms
+    optparse-applicative
+    pretty
+    process
+    QuickCheck
+    stm
+    tagged
+    tar
+    tasty
+    tasty-golden
+    tasty-hunit
+    tasty-quickcheck
+    temporary
+    text
+    tree-diff
+  ];
+  doCheck = false;
+  homepage = "http://www.haskell.org/cabal/";
+  description = "A framework for packaging Haskell software";
+  license = stdenv.lib.licenses.bsd3;
+}

nix/overlays/haskell-packages/README.md

@@ -2,9 +2,9 @@ The `.nix` files in this directory pin specific versions of Haskell packages
 from Hackage. They were generated with `cabal2nix`, e.g.:
 
 ```bash
-cabal2nix cabal://protolude > protolude.nix
+cabal2nix cabal://Cabal-3.0.0.0 > Cabal.nix
 
 ```
 
-Those overrides might become obsolete as the pinned versions are adopted into
-our pinned version of nixpkgs.
+Those overrides will likely become obsolete as the pinned versions are adopted
+into our pinned version of nixpkgs.

nix/overlays/haskell-packages/default.nix

@@ -1,11 +1,37 @@
-self: super:
+{ compiler, static ? false }:
 
+self: super:
+let
+  lib =
+    self.haskell.lib;
+
+  overrides =
+    final: prev:
+    rec {
+      protolude =
+        prev.callHackageDirect
+          {
+            pkg = "protolude";
+            ver = "0.3.0";
+            sha256 = "0iwh4wsjhb7pms88lw1afhdal9f86nrrkkvv65f9wxbd1b159n72";
+          } { };
+
+      cabal2nix =
+        if static then
+        # cabal2nix depends on Cabal 3.0.*, while our pinned version of
+        # Nixpkgs only provides 2.4 or 3.2. So we pinned 3.0.0.0 in
+        # ./Cabal.nix
+          prev.cabal2nix.overrideScope (self: super: { Cabal = self.callPackage ./Cabal.nix { }; })
+        else
+          prev.cabal2nix;
+    };
+in
 {
-  haskellPackages =
-    super.haskellPackages.override {
-      overrides =
-        final: prev: rec {
-          protolude = prev.callPackage ./protolude.nix {};
-        };
+  haskell =
+    super.haskell // {
+      packages = super.haskell.packages // {
+        "${compiler}" =
+          super.haskell.packages."${compiler}".override { inherit overrides; };
+      };
     };
 }

nix/overlays/haskell-packages/protolude.nix

@@ -1,43 +0,0 @@
-{ mkDerivation
-, array
-, async
-, base
-, bytestring
-, containers
-, deepseq
-, ghc-prim
-, hashable
-, mtl
-, mtl-compat
-, stdenv
-, stm
-, text
-, transformers
-, transformers-compat
-}:
-mkDerivation {
-  pname = "protolude";
-  version = "0.3.0";
-  sha256 = "4083385a9e03fab9201f63ce198b9ced3fbc1c50d6d42574db5e36c757bedcac";
-  isLibrary = true;
-  isExecutable = true;
-  libraryHaskellDepends = [
-    array
-    async
-    base
-    bytestring
-    containers
-    deepseq
-    ghc-prim
-    hashable
-    mtl
-    mtl-compat
-    stm
-    text
-    transformers
-    transformers-compat
-  ];
-  homepage = "https://github.com/sdiehl/protolude";
-  description = "A small prelude";
-  license = stdenv.lib.licenses.mit;
-}

nix/overlays/postgresql-default.nix

@@ -0,0 +1,5 @@
+self: super:
+# Overlay that sets the default version of PostgreSQL.
+{
+  postgresql = super.postgresql_12;
+}

nix/overlays/postgresql-legacy.nix

@@ -16,5 +16,5 @@ self: super:
           sha256 = tarballHash;
         };
     in
-      (import pinnedPkgs {}).pkgs.postgresql_9_4;
+    (import pinnedPkgs { }).pkgs.postgresql_9_4;
 }