format with nixpkgs-fmt

I also couldn't help myself to change the `with { ... }` blocks
 to `let ... in` blocks.

default.nix

@@ -3,19 +3,25 @@
 }:
 
 with rec
-{ files = pkgs.callPackage ./nix/files.nix {};
+{
+  files = pkgs.callPackage ./nix/files.nix {};
+
   sourceByRegex = name: src: regexes:
-    builtins.path
+    builtins.path {
-      { filter =  (path: type:
+      filter = (
+        path: type:
           let
             relPath = pkgs.lib.removePrefix (toString src + "/") (toString path);
             accept = pkgs.lib.any (re: builtins.match re relPath != null) regexes;
-          in accept);
+          in
+            accept
+      );
       inherit name;
       path = src;
     };
-  niv-source = sourceByRegex "niv" ./.
+
-    [ "^package.yaml$"
+  niv-source = sourceByRegex "niv" ./. [
+    "^package.yaml$"
     "^README.md$"
     "^LICENSE$"
     "^app$"
@@ -30,14 +36,18 @@ with rec
     "^nix.sources.nix$"
   ];
 
-  haskellPackages = pkgs.haskellPackages.override
+  haskellPackages = pkgs.haskellPackages.override {
-    { overrides = _: haskellPackages:
+    overrides = _: haskellPackages: {
-        { niv =
+      niv =
         pkgs.haskell.lib.failOnAllWarnings (
           pkgs.haskell.lib.disableExecutableProfiling (
             pkgs.haskell.lib.disableLibraryProfiling (
               pkgs.haskell.lib.generateOptparseApplicativeCompletion "niv" (
-            haskellPackages.callCabal2nix "niv" niv-source {}))));
+                haskellPackages.callCabal2nix "niv" niv-source {}
+              )
+            )
+          )
+        );
     };
   };
 
@@ -46,9 +56,9 @@ with rec
   niv-sdist = pkgs.haskell.lib.sdistTarball niv;
 
   niv-cabal-upload =
-    with
+    let
-      {  niv-version = niv.version;
+      niv-version = niv.version;
-      };
+    in
       pkgs.writeScript "cabal-upload"
         ''
           #!${pkgs.stdenv.shell}
@@ -127,10 +137,9 @@ with rec
   # In order to make `Paths_niv(version)` available in `ghci`, we parse the
   # version from `package.yaml` and create a dummy module that we inject in the
   # `ghci` command.
-  niv-devshell = haskellPackages.shellFor
+  niv-devshell = haskellPackages.shellFor {
-    { packages = (ps: [ ps.niv ]);
+    packages = ps: [ ps.niv ];
-      shellHook =
+    shellHook = ''
-        ''
       repl_for() {
         haskell_version=$(cat ./package.yaml \
           | grep -oP 'version: \K\d+.\d+.\d+' \
@@ -169,34 +178,35 @@ with rec
       echo "  ..."
     '';
   };
-
 };
 rec
-{ inherit niv niv-sdist niv-source niv-devshell niv-cabal-upload;
+{
+  inherit niv niv-sdist niv-source niv-devshell niv-cabal-upload;
 
   tests = pkgs.callPackage ./tests { inherit niv; };
 
   niv-test = pkgs.runCommand "niv-test" { buildInputs = [ niv ]; }
     "niv-test && touch $out";
 
-  readme = pkgs.writeText "README.md"
+  readme = pkgs.writeText "README.md" (
-    (with
+    let
-      { template = builtins.readFile ./README.tpl.md;
+      template = builtins.readFile ./README.tpl.md;
-        niv_help = builtins.readFile
+      niv_help = builtins.readFile (
-          (pkgs.runCommand "niv_help" { buildInputs = [ niv ]; }
+        pkgs.runCommand "niv_help" { buildInputs = [ niv ]; }
           "niv --help > $out"
       );
-        niv_cmd_help = cmd: builtins.readFile
+      niv_cmd_help = cmd: builtins.readFile (
-          (pkgs.runCommand "niv_${cmd}_help" { buildInputs = [ niv ]; }
+        pkgs.runCommand "niv_${cmd}_help" { buildInputs = [ niv ]; }
           "niv ${cmd} --help > $out"
       );
       cmds = [ "add" "update" "drop" "init" "show" ];
-      };
+    in
       pkgs.lib.replaceStrings
         ([ "replace_niv_help" ] ++ (map (cmd: "replace_niv_${cmd}_help") cmds))
         ([ niv_help ] ++ (map niv_cmd_help cmds))
         template
   );
+
   readme-test = pkgs.runCommand "README-test" {}
     ''
       err() {
@@ -235,7 +245,6 @@ rec
       [ $expected_hash == $actual_hash ] && echo dymmy > $out || err
     '';
 
-
   # TODO: use nivForTest for this one
   niv-svg-cmds = pkgs.writeScript "niv-svg-cmds"
     ''
@@ -263,5 +272,4 @@ rec
       echo done rendering
       popd
     '';
-
 }

nix/default.nix

@@ -1,13 +1,8 @@
 { sources ? import ./sources.nix }:
-import sources.nixpkgs
+import sources.nixpkgs {
-  { overlays =
+  overlays = [
-    [ (_: pkgs:
+    (_: pkgs: { inherit sources; })
-        { inherit sources; }
+    (_: pkgs: { termtosvg = pkgs.callPackage ./termtosvg.nix {}; })
-      )
-      (_: pkgs:
-        { termtosvg = pkgs.callPackage ./termtosvg.nix {}; }
-      )
-
   ];
   config = {};
 }

nix/sources.nix

@@ -22,8 +22,7 @@ with rec
       '';
 
   # fetchTarball version that is compatible between all the versions of Nix
-  builtins_fetchTarball =
+  builtins_fetchTarball = { url, sha256 }@attrs:
-      { url, sha256 }@attrs:
     let
       inherit (builtins) lessThan nixVersion fetchTarball;
     in
@@ -33,8 +32,7 @@ with rec
         fetchTarball attrs;
 
   # fetchurl version that is compatible between all the versions of Nix
-  builtins_fetchurl =
+  builtins_fetchurl = { url, sha256 }@attrs:
-      { url, sha256 }@attrs:
     let
       inherit (builtins) lessThan nixVersion fetchurl;
     in
@@ -57,22 +55,27 @@ with rec
 
   sources = builtins.fromJSON (builtins.readFile ./sources.json);
 
-  mapAttrs = builtins.mapAttrs or
+  mapAttrs = builtins.mapAttrs or (
-    (f: set: with builtins;
+    f: set: with builtins;
-      listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set)));
+    listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
+  );
 
   # borrowed from nixpkgs
   functionArgs = f: f.__functionArgs or (builtins.functionArgs f);
   callFunctionWith = autoArgs: f: args:
-    let auto = builtins.intersectAttrs (functionArgs f) autoArgs;
+    let
-    in f (auto // args);
+      auto = builtins.intersectAttrs (functionArgs f) autoArgs;
+    in
+      f (auto // args);
 
   getFetcher = spec:
-    let fetcherName =
+    let
+      fetcherName =
         if builtins.hasAttr "type" spec
         then builtins.getAttr "type" spec
         else "builtin-tarball";
-    in builtins.getAttr fetcherName {
+    in
+      builtins.getAttr fetcherName {
         "tarball" = fetchzip;
         "builtin-tarball" = builtins_fetchTarball;
         "file" = fetchurl;
@@ -80,14 +83,14 @@ with rec
       };
 };
 # NOTE: spec must _not_ have an "outPath" attribute
-mapAttrs (_: spec:
+mapAttrs (
+  _: spec:
     if builtins.hasAttr "outPath" spec
     then abort
       "The values in sources.json should not have an 'outPath' attribute"
     else
       if builtins.hasAttr "url" spec && builtins.hasAttr "sha256" spec
       then
-      spec //
+        spec // { outPath = callFunctionWith spec (getFetcher spec) {}; }
-      { outPath = callFunctionWith spec (getFetcher spec) { }; }
       else spec
 ) sources

tests/default.nix

@@ -18,9 +18,11 @@ let
   niv_HEAD = "a489b65a5c3a29983701069d1ce395b23d9bde64";
   niv_HEAD- = "abc51449406ba3279c466b4d356b4ae8522ceb58";
   nixpkgs-channels_HEAD = "571b40d3f50466d3e91c1e609d372de96d782793";
-in pkgs.runCommand "test"
+in
-    { buildInputs =
+pkgs.runCommand "test"
-        [ pkgs.haskellPackages.wai-app-static
+  {
+    buildInputs = [
+      pkgs.haskellPackages.wai-app-static
       niv
       pkgs.nix
       pkgs.jq