chore: initial commit

lib/modules/main.nix

@@ -0,0 +1,113 @@
+{
+  pkgs,
+  lib ? pkgs.lib,
+  config,
+  ...
+}: let
+  inherit (lib) mapAttrs mkOption types textClosureMap id attrNames;
+  mkNakedShell = pkgs.callPackage ./../utils/mkNakedShell.nix {};
+
+  addAttributeName = prefix:
+    mapAttrs (
+      k: v:
+        v
+        // {
+          text = ''
+            #### ${prefix}.${k}
+            ${v.text}
+          '';
+        }
+    );
+
+  envBash =
+    pkgs.writeText "devshell-env.bash"
+    # sh
+    ''
+      export DEVSHELL_DIR=@DEVSHELL_DIR@
+      # nicely handle it at the front or between/end
+      PATH=''${PATH#/path-not-set:}
+      PATH=''${PATH#:/path-not-set}
+      export PATH=$DEVSHELL_DIR/bin:$PATH
+
+      ${textClosureMap
+        id
+        (addAttributeName "startup" config.enterShellCommands)
+        (attrNames config.enterShellCommands)}
+
+      # interactive session
+      if [[ $- == *i* ]]; then
+        true
+        ${textClosureMap
+        id
+        (addAttributeName "interactive" config.interactiveShellCommands)
+        (attrNames config.interactiveShellCommands)}
+      fi # interactive session
+
+      unset DEVSHELL_DIR
+    '';
+
+  entryType = types.submodule {
+    options = {
+      text = mkOption {
+        type = types.str;
+        description = ''
+          Script to run.
+        '';
+      };
+
+      deps = mkOption {
+        type = types.listOf types.str;
+        default = [];
+        description = ''
+          A list of other steps that this one depends on.
+        '';
+      };
+    };
+  };
+in {
+  options = {
+    shell = {
+      finalPackage = mkOption {
+        type = types.package;
+        internal = true;
+      };
+      finalProfile = mkOption {
+        type = types.package;
+        internal = true;
+      };
+    };
+
+    name = mkOption {
+      type = types.str;
+      default = "devshell";
+    };
+    packages = mkOption {
+      type = types.listOf types.package;
+      default = [];
+    };
+    enterShellCommands = mkOption {
+      type = types.attrsOf entryType;
+      default = {};
+    };
+    interactiveShellCommands = mkOption {
+      type = types.attrsOf entryType;
+      default = {};
+    };
+  };
+
+  config.shell = {
+    finalProfile = pkgs.buildEnv {
+      name = "${config.name}-profile";
+      paths = config.packages;
+      postBuild = ''
+        substitute ${envBash} $out/env.bash --subst-var-by DEVSHELL_DIR $out
+        # NOTE: maybe also add an entrypoint shell script at $out/bin/devshell-${config.name}?
+      '';
+      meta.mainProgram = "devshell-${config.name}";
+    };
+    finalPackage = mkNakedShell {
+      name = config.name;
+      profile = config.shell.finalProfile;
+    };
+  };
+}