nix: only set `CONDUIT_VERSION_EXTRA` for final build + slight cleanup

Signed-off-by: strawberry <strawberry@puppygock.gay>

nix/pkgs/main/default.nix

-{ inputs
-
-# Dependencies
-, craneLib
+# Dependencies (keep sorted)
+{ craneLib
+, inputs
 , lib
 , libiconv
 , pkgsBuildHost
@@ -9,54 +8,72 @@
 , rust
 , stdenv
 
-# Options
+# Options (keep sorted)
 , default_features ? true
 , features ? []
 , profile ? "release"
 }:
 
-craneLib.buildPackage rec {
-  src = inputs.nix-filter {
-    root = inputs.self;
-    include = [
-      "src"
-      "hot_lib"
-      "Cargo.toml"
-      "Cargo.lock"
-    ];
-  };
+let
+buildDepsOnlyEnv =
+  let
+    rocksdb' = rocksdb.override {
+      enableJemalloc = builtins.elem "jemalloc" features;
+    };
+  in
+  {
+    CARGO_PROFILE = profile;
+    ROCKSDB_INCLUDE_DIR = "${rocksdb'}/include";
+    ROCKSDB_LIB_DIR = "${rocksdb'}/lib";
+  }
+  //
+  (import ./cross-compilation-env.nix {
+    # Keep sorted
+    inherit
+      lib
+      pkgsBuildHost
+      rust
+      stdenv;
+  });
 
-  # This is redundant with CI
-  doCheck = false;
+buildPackageEnv = {
+  CONDUIT_VERSION_EXTRA = inputs.self.shortRev or inputs.self.dirtyShortRev;
+} // buildDepsOnlyEnv;
+
+commonAttrs = {
+  inherit
+    (craneLib.crateNameFromCargoToml {
+      cargoToml = "${inputs.self}/Cargo.toml";
+    })
+    pname
+    version;
+
+    src = let filter = inputs.nix-filter.lib; in filter {
+      root = inputs.self;
 
-  env =
-    let
-      rocksdb' = rocksdb.override {
-        enableJemalloc = builtins.elem "jemalloc" features;
-      };
-    in
-    {
-      CARGO_PROFILE = profile;
-      CONDUIT_VERSION_EXTRA = inputs.self.shortRev or inputs.self.dirtyShortRev;
-      ROCKSDB_INCLUDE_DIR = "${rocksdb'}/include";
-      ROCKSDB_LIB_DIR = "${rocksdb'}/lib";
-    }
-    //
-    (import ./cross-compilation-env.nix {
-      inherit
-        lib
-        pkgsBuildHost
-        rust
-        stdenv;
-    });
+      # Keep sorted
+      include = [
+        "Cargo.lock"
+        "Cargo.toml"
+        "hot_lib"
+        "src"
+      ];
+    };
 
-  nativeBuildInputs = [
-    # bindgen needs the build platform's libclang. Apparently due to "splicing
-    # weirdness", pkgs.rustPlatform.bindgenHook on its own doesn't quite do the
-    # right thing here.
-    pkgsBuildHost.rustPlatform.bindgenHook
+    nativeBuildInputs = [
+      # bindgen needs the build platform's libclang. Apparently due to "splicing
+      # weirdness", pkgs.rustPlatform.bindgenHook on its own doesn't quite do the
+      # right thing here.
+      pkgsBuildHost.rustPlatform.bindgenHook
   ]
   ++ lib.optionals stdenv.isDarwin [ libiconv ];
+ };
+in
+
+craneLib.buildPackage ( commonAttrs // {
+  cargoArtifacts = craneLib.buildDepsOnly (commonAttrs // {
+    env = buildDepsOnlyEnv;
+  });
 
   cargoExtraArgs = ""
     + lib.optionalString
@@ -66,11 +83,14 @@ craneLib.buildPackage rec {
       (features != [])
       "--features " + (builtins.concatStringsSep "," features);
 
-  meta.mainProgram = (craneLib.crateNameFromCargoToml {
-    cargoToml = "${inputs.self}/Cargo.toml";
-  }).pname;
+  # This is redundant with CI
+  doCheck = false;
+
+  env = buildPackageEnv;
 
   passthru = {
-    inherit env;
+    env = buildPackageEnv;
   };
-}
+
+  meta.mainProgram = commonAttrs.pname;
+})