Some improvements.

- removed double substitution when generating flake.nix

- make gen-flake use shellcheck via writeShellApplication

- use --show-trace when testing

- add nix-systems/default on resulting flake.

Author: vic

flake.nix

@@ -99,44 +99,32 @@
           '';
         };
 
-        genFlakes =
-          let
-            flake = pkgs.substitute {
-              src = ./lib/devshell-flake.nix;
-              substitutions = [
-                "--replace-fail"
-                ''inputs.source.url = "path:empty"''
-                ''inputs.source.url = "path:SOURCE_URL"''
-                "--replace-fail"
-                ''inputs.config.url = "path:empty"''
-                ''inputs.config.url = "path:CONFIG_URL"''
-              ];
-            };
-          in
-          pkgs.writeShellScriptBin "gen-flakes" ''
-            export PATH="${
-              with pkgs;
-              lib.makeBinPath [
-                coreutils
-                gnused
-                nix
-              ]
-            }"
-
+        genFlakes = pkgs.writeShellApplication {
+          name = "gen-flakes";
+          runtimeInputs = with pkgs; [
+            coreutils
+            gnused
+            nix
+          ];
+          text = ''
             SOURCE_DIR="$1"
-            SOURCE_FLAKE="$2"
+            FLAKE_DEST="$2"
 
-            mkdir -p "$SOURCE_FLAKE/config"
+            mkdir -p "$FLAKE_DEST/config"
+            sed -e "s#path:./source#path:$SOURCE_DIR#" ${./lib/devshell-flake.nix} > "$FLAKE_DEST/flake.nix"
 
             if test -e "$SOURCE_DIR/flake.toml"; then
-              nix eval --file ${./lib/make-config-flake.nix} --apply "f: f $SOURCE_DIR/flake.toml" --raw --impure --offline | \
-                sed -e "s#url = \"path:./#url = \"path:$SOURCE_DIR/#g" > "$SOURCE_FLAKE/config/flake.nix"
+              nix eval \
+                --file ${./lib/make-config-flake.nix} \
+                --apply "f: f $SOURCE_DIR/flake.toml" \
+                --extra-experimental-features "flakes nix-command" \
+                --raw --impure --offline |\
+                sed -e "s#url = \"path:./#url = \"path:$SOURCE_DIR/#g" > "$FLAKE_DEST/config/flake.nix"
             else
-              cp -f ${./lib/empty-config-flake.nix} "$SOURCE_FLAKE/config/flake.nix"
+              cp -f ${./lib/empty-config-flake.nix} "$FLAKE_DEST/config/flake.nix"
             fi
-
-            sed -e "s#SOURCE_URL#$SOURCE_DIR#; s#CONFIG_URL#$SOURCE_FLAKE/config#" ${flake} > "$SOURCE_FLAKE/flake.nix"
           '';
+        };
       };
 
       apps = perSystem (

lib/devshell-flake.nix

@@ -1,34 +1,29 @@
 {
   inputs.devshell.url = "github:numtide/devshell";
+  inputs.systems.url = "github:nix-systems/default";
 
-  inputs.source.url = "path:empty";
+  inputs.source.url = "path:./source";
   inputs.source.flake = false;
 
-  inputs.config.url = "path:empty";
+  inputs.config.url = "path:./config";
 
   outputs =
-    inputs@{
-      # deadnix: skip
-      nixpkgs,
-      ...
-    }:
+    inputs:
     let
-      toml-file = "${inputs.source.outPath}/devshell.toml";
-
       ins = inputs // inputs.config.inputs;
-      nixpkgs = ins.nixpkgs;
+      devshell_toml = ins.source + "/devshell.toml";
+
+      nixpkgs = ins.nixpkgs or ins.devshell.inputs.nixpkgs;
+      perSystem = nixpkgs.lib.genAttrs (import ins.systems);
 
-      perSystem = nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed;
+      nix-config = ins.config.lib.nix-config or { };
+      overlays-config = ins.config.lib.overlays or [ ];
+      attr-overlay = name: value: [ ins.${name}.overlays.${value} ];
+      overlays = with nixpkgs.lib; flatten (map (mapAttrsToList attr-overlay) overlays-config);
 
       devShells = perSystem (
         system:
         let
-
-          nix-config = ins.config.lib.nix-config or { };
-          overlays-config = ins.config.lib.overlays or [ ];
-          attr-overlay = name: value: [ ins.${name}.overlays.${value} ];
-          overlays = with nixpkgs.lib; flatten (map (mapAttrsToList attr-overlay) overlays-config);
-
           pkgs = import nixpkgs {
             inherit system;
             config = nix-config;
@@ -39,7 +34,7 @@
             _module.args = {
               inputs = ins;
             };
-            imports = [ (pkgs.devshell.importTOML toml-file) ];
+            imports = [ (pkgs.devshell.importTOML devshell_toml) ];
           };
         in
         {

test-templates.bash

@@ -19,11 +19,11 @@ function test_template() {
 
     cp -rf "$base/$template"/* "$out/"
 
-    nix run "path:$base"
+    nix run "path:$base" --show-trace
     test -e "$HOME/.config/direnv/lib/use_devshell_toml.sh"
 
     # use bash strict inside .envrc
-    echo "set -euo pipefail; source $HOME/.config/direnv/lib/use_devshell_toml.sh; use devshell_toml" > "$out/.envrc"
+    echo "set -euo pipefail; source $HOME/.config/direnv/lib/use_devshell_toml.sh; use devshell_toml --show-trace" > "$out/.envrc"
 
     direnv allow "$out"
     direnv exec "$out" check