Expose executables from Cabal packages

Author: sellout

flake.nix

@@ -144,6 +144,37 @@
           });
       };
 
+      apps = let ## TODO: Move these functions to the lib.
+        ## Define a single entry for flake `apps` from the path in the Nix store
+        ## for a Cabal package and executable defined in that package.
+        cabalApp = package: executable: {
+          program = "${inputs.self.packages.${system}."${defaultCompiler}_${package}"}/bin/${executable}";
+          type = "app";
+        };
+
+        ## Given a path in the Nix store for a Cabal package and a list of
+        ## executables defined in the Cabal package, creates an AttrSet of apps,
+        ## one per listed executable.
+        ##
+        ## TODO: Somehow extract this, if possible, from `callCabal2nix` result.
+        cabalApps = package: executables:
+          builtins.listToAttrs
+          (map (exe: {name = exe; value = cabalApp package exe;}) executables);
+
+        ## Given an AttrSet with the keys being paths in the Nix store for Cabal
+        ## packages and the values being lists of executables defined in that
+        ## Cabal package, creates an AttrSet of apps, one per listed executable.
+        ##
+        ## TODO: Somehow extract this, if possible, from `cabalProject2nix`
+        ##       result.
+        cabalProjectApps = pkgs.lib.concatMapAttrs cabalApps;
+      in cabalProjectApps {
+        concat-graphics = ["graphics-examples" "graphics-trace"];
+        ## TODO: concat-hardware currently doesn’t build
+        # concat-hardware = ["hardware-examples" "hardware-trace"];
+        concat-plugin = ["misc-examples" "misc-trace"];
+      };
+
       # Nix code formatter, https://github.com/kamadorueda/alejandra#readme
       formatter = pkgs.alejandra;
     });