translators/cabal-freeze: Read name and version from cabal file

Also remove those fields from extraArgs.

examples/haskell_cabal-freeze/flake.nix

@@ -17,7 +17,6 @@
       {
         translator = "cabal-freeze";
       }
-      {subsystemInfo = {defaultPackageName = "unordered-containers";};}
     ];
   });
 }

src/subsystems/haskell/translators/cabal-freeze/default.nix

@@ -112,8 +112,6 @@ in {
     tree,
     # arguments defined in `extraArgs` (see below) specified by user
     ghcVersion,
-    defaultPackageName,
-    defaultPackageVersion,
     ...
   } @ args: let
     # get the root source and project source
@@ -121,6 +119,29 @@ in {
     projectSource = "${tree.fullPath}/${project.relPath}";
     projectTree = tree.getNodeFromPath project.relPath;
 
+    # FIXME: This is the first of many snippets that will need to be modified to support multiple packages
+    cabalFileText = l.pipe projectTree.files [
+      l.attrNames
+      (
+        l.findFirst (l.hasSuffix ".cabal")
+        (throw "No cabal file in the tree")
+      )
+      projectTree.getNodeFromPath
+      (l.attrByPath ["fullPath"] "")
+      dlib.readTextFile
+      (s: "\n" + s)
+    ];
+
+    defaultPackageName = l.pipe cabalFileText [
+      (l.match ".*\nname:[[:space:]]+([^[:space:]]+).*")
+      l.head
+    ];
+
+    defaultPackageVersion = l.pipe cabalFileText [
+      (l.match ".*\nversion:[[:space:]]+([^[:space:]]+).*")
+      l.head
+    ];
+
     parsedCabalFreeze = l.pipe projectTree.files [
       l.attrNames
       (
@@ -277,19 +298,5 @@ in {
       examples = ["9.0.2" "9.4.1"];
       type = "argument";
     };
-
-    defaultPackageName = {
-      description = "Name of default package";
-      default = "main";
-      examples = ["main" "default"];
-      type = "argument";
-    };
-
-    defaultPackageVersion = {
-      description = "Version of default package";
-      default = "unknown";
-      examples = ["unknown" "1.2.0"];
-      type = "argument";
-    };
   };
 }