From 0327c07701bd5c6a4fa6de2baf898818efe60b96 Mon Sep 17 00:00:00 2001
From: Sridhar Ratnakumar <srid@srid.ca>
Date: Sun, 22 Dec 2024 20:39:25 -0500
Subject: [PATCH] refactor: consolidate in one place

---
 nix/build-haskell-package.nix            | 59 ++++++++++++++----------
 nix/modules/project/packages/default.nix |  9 +---
 nix/modules/project/packages/package.nix |  4 +-
 3 files changed, 37 insertions(+), 35 deletions(-)

diff --git a/nix/build-haskell-package.nix b/nix/build-haskell-package.nix
index f0da63d2..0b2cf296 100644
--- a/nix/build-haskell-package.nix
+++ b/nix/build-haskell-package.nix
@@ -12,7 +12,7 @@
 }:
 
 let
-  mkNewStorePath = name: src:
+  mkNewStorePath' = name: src:
     # Since 'src' may be a subdirectory of a store path
     # (in string form, which means that it isn't automatically
     # copied), the purpose of cleanSourceWith here is to create a
@@ -23,29 +23,38 @@ let
       inherit src;
     };
 
-in
+  # Avoid rebuilding because of changes in parent directories
+  mkNewStorePath = name: src:
+    let newSrc = mkNewStorePath' name src;
+    in log.traceDebug "${name}.mkNewStorePath ${newSrc}" newSrc;
+
+  callCabal2nix = name: src:
+    let pkg = self.callCabal2nix name src { };
+    in log.traceDebug "${name}.callCabal2nix src=${src} deriver=${pkg.cabal2nixDeriver.outPath}" pkg;
 
-name: root: cabal2NixFile:
-lib.pipe root
-  [
-    # Avoid rebuilding because of changes in parent directories
-    (mkNewStorePath "source-${name}")
-    (x: log.traceDebug "${name}.mkNewStorePath ${x.outPath}" x)
+  # Use cached cabal2nix generated nix expression if present, otherwise use IFD (callCabal2nix)
+  callCabal2NixUnlessCached = name: src: cabal2nixFile:
+    let path = "${src}/${cabal2nixFile}";
+    in
+    if builtins.pathExists path
+    then
+      callPackage name path
+    else
+      callCabal2nix name src { };
+
+  callPackage = name: nixFilePath:
+    let pkg = self.callPackage nixFilePath { };
+    in log.traceDebug "${name}.callPackage[cabal2nix] ${nixFilePath}" pkg;
+
+  callHackage = name: version:
+    let pkg = self.callHackage name version { };
+    in log.traceDebug "${name}.callHackage ver=${version}" pkg;
+in
 
-    (root:
-      let path = "${root}/${cabal2NixFile}";
-      in
-      # Check if cached cabal2nix generated nix expression is present,
-        # if present use it with callPackage
-        # to avoid IFD
-      if builtins.pathExists path
-      then
-        (log.traceDebug "${name}.callPackage[cabal2nix] ${path}")
-          (self.callPackage path { })
-      else
-        lib.pipe (self.callCabal2nix name root { })
-          [
-            (pkg: log.traceDebug "${name}.callCabal2nix root=${root} deriver=${pkg.cabal2nixDeriver.outPath}" pkg)
-          ]
-    )
-  ]
+name: cfg:
+# If 'source' is a path, we treat it as such. Otherwise, we assume it's a version (from hackage).
+if lib.types.path.check cfg.source
+then
+  callCabal2NixUnlessCached name (mkNewStorePath name cfg.source) cfg.cabal2NixFile
+else
+  callHackage name cfg.source
diff --git a/nix/modules/project/packages/default.nix b/nix/modules/project/packages/default.nix
index 6a8b7cd0..6bcd6e6e 100644
--- a/nix/modules/project/packages/default.nix
+++ b/nix/modules/project/packages/default.nix
@@ -58,15 +58,8 @@ in
           build-haskell-package = import ../../../build-haskell-package.nix {
             inherit pkgs lib self log;
           };
-          getOrMkPackage = name: cfg:
-            if lib.types.path.check cfg.source
-            then
-              (build-haskell-package name cfg.source cfg.cabal2NixFile)
-            else
-              log.traceDebug "${name}.callHackage ${cfg.source}"
-                (self.callHackage name cfg.source { });
         in
-        lib.mapAttrs getOrMkPackage project.config.packages;
+        lib.mapAttrs build-haskell-package project.config.packages;
     };
   };
 }
diff --git a/nix/modules/project/packages/package.nix b/nix/modules/project/packages/package.nix
index bbf74e1a..21a5c960 100644
--- a/nix/modules/project/packages/package.nix
+++ b/nix/modules/project/packages/package.nix
@@ -26,9 +26,9 @@ in
     cabal2NixFile = lib.mkOption {
       type = lib.types.str;
       description = ''
-        The Nix file which contains cached (pre-generated) `cabal2nix` expressions.
+        Filename of the cabal2nix generated nix expression.
 
-        By default, it refers to `cabal.nix` file.
+        This gets used if it exists instead of using IFD (callCabal2nix).
       '';
       default = "cabal.nix";
     };