refactor: statix recommendations (#363)

* refactor: Inherit where possible

As recommended by `statix check`.

* refactor: Remove unnecessary parentheses

As recommended by `statix check`.

* refactor: Remove unnecessary comparison with `true`

As recommended by `statix check`.

* refactor: Avoid using deprecated `isNull`

As recommended by `statix check` and the documentation
<https://nixos.org/manual/nix/stable/language/builtins.html#builtins-isNull>.

* refactor: Simplify conditionals

As recommended by `statix check`.

* Update sources version

---------

Co-authored-by: Nicolas Mattia <nicolas@nmattia.com>

default.nix

@@ -7,14 +7,12 @@ let
 
   sourceByRegex = name: src: regexes:
     builtins.path {
-      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
-      );
+      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;
       inherit name;
       path = src;
     };
@@ -61,7 +59,7 @@ let
     };
   };
 
-  niv = haskellPackages.niv;
+  inherit (haskellPackages) niv;
 
   niv-sdist = pkgs.haskell.lib.sdistTarball niv;
 

foo/default.nix

@@ -65,7 +65,7 @@
         { mkDerivation }:
         mkDerivation {
           pname = spec.name;
-          version = spec.version;
+          inherit (spec) version;
           inherit src;
           isLibrary = builtins.hasAttr "library" spec;
           isExecutable = builtins.hasAttr "executables" spec;

nix/sources.nix

@@ -27,16 +27,17 @@ let
   fetch_git = name: spec:
     let
       ref =
-        if spec ? ref then spec.ref else
-        if spec ? branch then "refs/heads/${spec.branch}" else
-        if spec ? tag then "refs/tags/${spec.tag}" else
-        abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!";
-      submodules = if spec ? submodules then spec.submodules else false;
+        spec.ref or (
+          if spec ? branch then "refs/heads/${spec.branch}" else
+          if spec ? tag then "refs/tags/${spec.tag}" else
+          abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!"
+        );
+      submodules = spec.submodules or false;
       submoduleArg =
         let
           nixSupportsSubmodules = builtins.compareVersions builtins.nixVersion "2.4" >= 0;
           emptyArgWithWarning =
-            if submodules == true
+            if submodules
             then
               builtins.trace
                 (
@@ -115,7 +116,7 @@ let
   # the path directly as opposed to the fetched source.
   replace = name: drv:
     let
-      saneName = stringAsChars (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name;
+      saneName = stringAsChars (c: if (builtins.match "[a-zA-Z0-9]" c) == null then "_" else c) name;
       ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
     in
     if ersatz == "" then drv else
@@ -151,7 +152,7 @@ let
       inherit (builtins) lessThan nixVersion fetchTarball;
     in
     if lessThan nixVersion "1.12" then
-      fetchTarball ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
+      fetchTarball ({ inherit url; } // (optionalAttrs (name != null) { inherit name; }))
     else
       fetchTarball attrs;
 
@@ -161,7 +162,7 @@ let
       inherit (builtins) lessThan nixVersion fetchurl;
     in
     if lessThan nixVersion "1.12" then
-      fetchurl ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
+      fetchurl ({ inherit url; } // (optionalAttrs (name != null) { inherit name; }))
     else
       fetchurl attrs;
 
@@ -182,7 +183,7 @@ let
   # The "config" used by the fetchers
   mkConfig =
     { sourcesFile ? if builtins.pathExists ./sources.json then ./sources.json else null
-    , sources ? if isNull sourcesFile then { } else builtins.fromJSON (builtins.readFile sourcesFile)
+    , sources ? if sourcesFile == null then { } else builtins.fromJSON (builtins.readFile sourcesFile)
     , system ? builtins.currentSystem
     , pkgs ? mkPkgs sources system
     }: rec {

src/Niv/Sources.hs

@@ -179,6 +179,7 @@ data SourcesNixVersion
   | -- Support submodules for git repos
     V27
   | -- formatting fix
+    -- Apply statix suggestions
     V28
   deriving stock (Bounded, Enum, Eq)
 
@@ -252,7 +253,7 @@ sourcesVersionToMD5 = \case
   V25 -> "6612caee5814670e5e4d9dd1b71b5f70"
   V26 -> "937bff93370a064c9000f13cec5867f9"
   V27 -> "8031ba9d8fbbc7401c800d0b84278ec8"
-  V28 -> "2ed0d91d652b28d99f14659144a0af28"
+  V28 -> "26ed55356db7673935329210a4f8c4a5"
 
 -- | The MD5 sum of ./nix/sources.nix
 sourcesNixMD5 :: IO T.Text