flutter: small refactorings in derivation

pkgs/development/compilers/flutter/default.nix

@@ -1,17 +1,22 @@
-{ callPackage, dart }:
+{ callPackage, fetchurl, dart }:
 let
   mkFlutter = opts: callPackage (import ./flutter.nix opts) { };
   getPatches = dir:
     let files = builtins.attrNames (builtins.readDir dir);
     in map (f: dir + ("/" + f)) files;
+  version = "1.22.4";
+  channel = "stable";
+  filename = "flutter_linux_${version}-${channel}.tar.xz";
 in
 {
   mkFlutter = mkFlutter;
   stable = mkFlutter rec {
-    inherit dart;
+    inherit dart version;
     pname = "flutter";
-    version = "1.22.4";
-    sha256Hash = "0qalgav9drqddcj8lfvl9ddf3325n953pvkmgha47lslg9sa88zw";
-    patches = getPatches ./patches/stable;
+    src = fetchurl {
+      url = "https://storage.googleapis.com/flutter_infra/releases/${channel}/linux/${filename}";
+      sha256 = "0qalgav9drqddcj8lfvl9ddf3325n953pvkmgha47lslg9sa88zw";
+    };
+    patches = getPatches ./patches;
   };
 }

pkgs/development/compilers/flutter/flutter.nix

@@ -1,10 +1,8 @@
 { pname
 , version
-, sha256Hash
 , patches
 , dart
-, channel ? "stable"
-, filename ? "flutter_linux_${version}-${channel}.tar.xz"
+, src
 }:
 
 { bash
@@ -33,19 +31,13 @@
 , systemd
 }:
 let
-  drvName = "flutter-${channel}-${version}";
+  drvName = "flutter-${version}";
   flutter = stdenv.mkDerivation {
     name = "${drvName}-unwrapped";
 
-    src = fetchurl {
-      url =
-        "https://storage.googleapis.com/flutter_infra/releases/${channel}/linux/${filename}";
-      sha256 = sha256Hash;
-    };
-
     buildInputs = [ git ];
 
-    inherit patches;
+    inherit src patches;
 
     postPatch = ''
       patchShebangs --build ./bin/
@@ -53,25 +45,29 @@ let
     '';
 
     buildPhase = ''
-      FLUTTER_ROOT=$(pwd)
-      FLUTTER_TOOLS_DIR="$FLUTTER_ROOT/packages/flutter_tools"
-      SNAPSHOT_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.snapshot"
-      STAMP_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.stamp"
-      SCRIPT_PATH="$FLUTTER_TOOLS_DIR/bin/flutter_tools.dart"
-      DART_SDK_PATH="${dart}"
+      export FLUTTER_ROOT="$(pwd)"
+      export FLUTTER_TOOLS_DIR="$FLUTTER_ROOT/packages/flutter_tools"
+      export SCRIPT_PATH="$FLUTTER_TOOLS_DIR/bin/flutter_tools.dart"
+
+      export SNAPSHOT_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.snapshot"
+      export STAMP_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.stamp"
+
+      export DART_SDK_PATH="${dart}"
 
       HOME=../.. # required for pub upgrade --offline, ~/.pub-cache
                  # path is relative otherwise it's replaced by /build/flutter
 
-      (cd "$FLUTTER_TOOLS_DIR" && ${dart}/bin/pub upgrade --offline)
+      pushd "$FLUTTER_TOOLS_DIR"
+      ${dart}/bin/pub get --offline
+      popd
 
       local revision="$(cd "$FLUTTER_ROOT"; git rev-parse HEAD)"
       ${dart}/bin/dart --snapshot="$SNAPSHOT_PATH" --packages="$FLUTTER_TOOLS_DIR/.packages" "$SCRIPT_PATH"
       echo "$revision" > "$STAMP_PATH"
       echo -n "${version}" > version
 
-      rm -rf bin/cache/{artifacts,dart-sdk,downloads}
-      rm -f  bin/cache/*.stamp
+      rm -r bin/cache/{artifacts,dart-sdk,downloads}
+      rm bin/cache/*.stamp
     '';
 
     installPhase = ''