postgresql: move postgresqlWithPackages to separate file

Moves the function to a separate file and makes it callPackage-able. Now
that buildEnv also supports finalAttrs, the finalPackage construct can
also be rewritten that way.

This gives us clear separation of concern between the package builder in
generic.nix and wrapper.nix.

pkgs/servers/sql/postgresql/generic.nix

@@ -39,7 +39,6 @@ let
       removeReferencesTo,
 
       # passthru
-      buildEnv,
       buildPackages,
       newScope,
       nixosTests,
@@ -542,10 +541,7 @@ let
           in
           import ./ext.nix newSelf newSuper;
 
-        withPackages = postgresqlWithPackages {
-          inherit buildEnv lib makeBinaryWrapper;
-          postgresql = finalAttrs.finalPackage;
-        };
+        withPackages = self.callPackage ./wrapper.nix { postgresql = finalAttrs.finalPackage; };
 
         pg_config = buildPackages.callPackage ./pg_config.nix {
           inherit (finalAttrs) finalPackage;
@@ -604,77 +600,6 @@ let
       };
     });
 
-  postgresqlWithPackages =
-    {
-      postgresql,
-      buildEnv,
-      lib,
-      makeBinaryWrapper,
-    }:
-    f:
-    let
-      installedExtensions = f postgresql.pkgs;
-      recurse = postgresqlWithPackages {
-        inherit
-          buildEnv
-          lib
-          makeBinaryWrapper
-          postgresql
-          ;
-      };
-      finalPackage = buildEnv {
-        pname = "${postgresql.pname}-and-plugins";
-        inherit (postgresql) version;
-        paths = installedExtensions ++ [
-          # consider keeping in-sync with `postBuild` below
-          postgresql
-          postgresql.man # in case user installs this into environment
-        ];
-
-        pathsToLink = [
-          "/"
-          "/bin"
-          "/share/postgresql/extension"
-          # Unbreaks Omnigres' build system
-          "/share/postgresql/timezonesets"
-          "/share/postgresql/tsearch_data"
-        ];
-
-        derivationArgs = {
-          strictDeps = true;
-          nativeBuildInputs = [ makeBinaryWrapper ];
-          postBuild =
-            let
-              args = lib.concatMap (ext: ext.wrapperArgs or [ ]) installedExtensions;
-            in
-            ''
-              wrapProgram "$out/bin/postgres" ${lib.concatStringsSep " " args}
-            '';
-        };
-
-        passthru = {
-          inherit installedExtensions;
-          inherit (postgresql)
-            pkgs
-            psqlSchema
-            ;
-
-          pg_config = postgresql.pg_config.override {
-            outputs = {
-              out = finalPackage;
-              man = finalPackage;
-            };
-          };
-
-          withJIT = recurse (_: installedExtensions ++ [ postgresql.jit ]);
-          withoutJIT = recurse (_: lib.remove postgresql.jit installedExtensions);
-
-          withPackages = f': recurse (ps: installedExtensions ++ f' ps);
-        };
-      };
-    in
-    finalPackage;
-
 in
 # passed by <major>.nix
 versionArgs:

pkgs/servers/sql/postgresql/wrapper.nix

@@ -0,0 +1,71 @@
+{
+  buildEnv,
+  callPackage,
+  lib,
+  makeBinaryWrapper,
+  postgresql,
+}:
+f:
+let
+  installedExtensions = f postgresql.pkgs;
+  recurse = import ./wrapper.nix {
+    # explicitly listed in case they were overridden
+    inherit
+      buildEnv
+      callPackage
+      lib
+      makeBinaryWrapper
+      postgresql
+      ;
+  };
+in
+buildEnv (finalAttrs: {
+  pname = "${postgresql.pname}-and-plugins";
+  inherit (postgresql) version;
+  paths = installedExtensions ++ [
+    # consider keeping in-sync with `postBuild` below
+    postgresql
+    postgresql.man # in case user installs this into environment
+  ];
+
+  pathsToLink = [
+    "/"
+    "/bin"
+    "/share/postgresql/extension"
+    # Unbreaks Omnigres' build system
+    "/share/postgresql/timezonesets"
+    "/share/postgresql/tsearch_data"
+  ];
+
+  derivationArgs = {
+    strictDeps = true;
+    nativeBuildInputs = [ makeBinaryWrapper ];
+    postBuild =
+      let
+        args = lib.concatMap (ext: ext.wrapperArgs or [ ]) installedExtensions;
+      in
+      ''
+        wrapProgram "$out/bin/postgres" ${lib.concatStringsSep " " args}
+      '';
+  };
+
+  passthru = {
+    inherit installedExtensions;
+    inherit (postgresql)
+      pkgs
+      psqlSchema
+      ;
+
+    pg_config = postgresql.pg_config.override {
+      outputs = {
+        out = finalAttrs.finalPackage;
+        man = finalAttrs.finalPackage;
+      };
+    };
+
+    withJIT = recurse (_: installedExtensions ++ [ postgresql.jit ]);
+    withoutJIT = recurse (_: lib.remove postgresql.jit installedExtensions);
+
+    withPackages = f': recurse (ps: installedExtensions ++ f' ps);
+  };
+})