feat: Provide a devShell with packages from enabled services (#355)

resolves #194

doc/devshell.md

@@ -0,0 +1,17 @@
+# DevShell
+
+`services-flake` uses [mkShell](https://nixos.org/manual/nixpkgs/stable/#sec-pkgs-mkShell) function to provide a shell with packages of all the enabled services.
+
+```nix
+# Inside `perSystem`
+{
+  process-compose."my-pc" = { ... };
+  devShells.default = pkgs.mkShell {
+    inputsFrom = [
+      config.process-compose."my-pc".services.outputs.devShell;
+    ];
+    # ...
+  };
+}
+```
+

doc/guide.md

@@ -2,4 +2,5 @@
 # Guide
 
 - [[datadir]]#
+- [[devshell]]#
 - [[custom-service]]#

example/share-services/northwind/flake.nix

@@ -18,13 +18,14 @@
       ];
       flake.processComposeModules.default =
         import ./services.nix { inherit inputs; };
-      perSystem = { self', pkgs, lib, ... }: {
+      perSystem = { self', pkgs, config, lib, ... }: {
         process-compose."default" = { config, ... }: {
           imports = [
             inputs.services-flake.processComposeModules.default
             inputs.self.processComposeModules.default
           ];
         };
+        devShells.default = config.process-compose."default".services.outputs.devShell;
       };
     };
 }

example/share-services/pgweb/flake.nix

@@ -15,7 +15,7 @@
       imports = [
         inputs.process-compose-flake.flakeModule
       ];
-      perSystem = { self', pkgs, lib, ... }: {
+      perSystem = { self', pkgs, config, lib, ... }: {
         process-compose."default" = { config, ... }: {
           imports = [
             inputs.services-flake.processComposeModules.default
@@ -32,6 +32,7 @@
             environment.PGWEB_DATABASE_URL = config.services.postgres.northwind.connectionURI { dbName = "sample"; };
           };
         };
+        devShells.default = config.process-compose."default".services.outputs.devShell;
       };
     };
 }

example/simple/flake.nix

@@ -16,7 +16,7 @@
       imports = [
         inputs.process-compose-flake.flakeModule
       ];
-      perSystem = { self', pkgs, lib, ... }: {
+      perSystem = { self', pkgs, config, lib, ... }: {
         # `process-compose.foo` will add a flake package output called "foo".
         # Therefore, this will add a default package that you can build using
         # `nix build` and run using `nix run`.
@@ -61,6 +61,9 @@
           };
 
         devShells.default = pkgs.mkShell {
+          inputsFrom = [
+            config.process-compose."default".services.outputs.devShell
+          ];
           nativeBuildInputs = [ pkgs.just ];
         };
       };

nix/services/default.nix

@@ -2,10 +2,11 @@ let
   inherit (import ../lib.nix) multiService;
 in
 {
-  imports = builtins.map multiService [
+  imports = (builtins.map multiService [
     ./apache-kafka.nix
     ./clickhouse
     ./elasticsearch.nix
+    ./mongodb.nix
     ./mysql
     ./nginx
     ./ollama.nix
@@ -23,6 +24,8 @@ in
     ./weaviate.nix
     ./searxng.nix
     ./tika.nix
-    ./mongodb.nix
+  ]) ++ [
+    ./devshell.nix
   ];
+
 }

nix/services/devshell.nix

@@ -0,0 +1,50 @@
+{ config, pkgs, lib, ... }:
+let
+  inherit (lib) types;
+in
+{
+  options.services.outputs = {
+    enabledServices = lib.mkOption {
+      type = types.attrsOf (types.listOf types.str);
+      readOnly = true;
+      description = ''
+        Names of all the enabled service instances, grouped by the service name.
+      '';
+      example = lib.literalExpression ''
+        {
+          mysql = [ "m1" "m2" ];
+          redis = [ "r1" ];
+        }
+      '';
+    };
+    devShell = lib.mkOption {
+      type = types.package;
+      readOnly = true;
+      description = ''
+        The devShell that aggregates packages from all the enabled services.
+      '';
+    };
+  };
+
+  config = {
+    services.outputs.enabledServices = lib.pipe config.services [
+      # `outputs` is a reserved attribute set and is not the name of a service.
+      (lib.filterAttrs (n: _: n != "outputs"))
+
+      (lib.mapAttrs (_service: instances:
+        lib.attrNames (lib.filterAttrs (_: v: v.enable) instances)))
+    ];
+
+    services.outputs.devShell = pkgs.mkShell {
+      packages = lib.pipe config.services.outputs.enabledServices [
+        (lib.mapAttrsToList (service: instances:
+          map
+            (instance:
+              lib.attrByPath ([ service instance "package" ]) (builtins.throw "${service}.${instance} doesn't define a `package` option") config.services)
+            instances))
+
+        lib.flatten
+      ];
+    };
+  };
+}