From 6e1251b57b40b234d1c4ed169d7cd422206396d7 Mon Sep 17 00:00:00 2001
From: Shivaraj B H <me@shivaraj-bh.in>
Date: Thu, 10 Oct 2024 22:04:55 +0530
Subject: [PATCH] feat: Provide a `devShell` with packages from enabled
 services (#355)

resolves #194
---
 doc/devshell.md                            | 17 ++++++++
 doc/guide.md                               |  1 +
 example/share-services/northwind/flake.nix |  3 +-
 example/share-services/pgweb/flake.nix     |  3 +-
 example/simple/flake.nix                   |  5 ++-
 nix/services/default.nix                   |  7 ++-
 nix/services/devshell.nix                  | 50 ++++++++++++++++++++++
 7 files changed, 81 insertions(+), 5 deletions(-)
 create mode 100644 doc/devshell.md
 create mode 100644 nix/services/devshell.nix

diff --git a/doc/devshell.md b/doc/devshell.md
new file mode 100644
index 00000000..8e8478a5
--- /dev/null
+++ b/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;
+    ];
+    # ...
+  };
+}
+```
+
diff --git a/doc/guide.md b/doc/guide.md
index 269ed11c..0b9c934b 100644
--- a/doc/guide.md
+++ b/doc/guide.md
@@ -2,4 +2,5 @@
 # Guide
 
 - [[datadir]]#
+- [[devshell]]#
 - [[custom-service]]#
diff --git a/example/share-services/northwind/flake.nix b/example/share-services/northwind/flake.nix
index 922eff1b..32589ba4 100644
--- a/example/share-services/northwind/flake.nix
+++ b/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;
       };
     };
 }
diff --git a/example/share-services/pgweb/flake.nix b/example/share-services/pgweb/flake.nix
index 1f6320b2..7cccd617 100644
--- a/example/share-services/pgweb/flake.nix
+++ b/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;
       };
     };
 }
diff --git a/example/simple/flake.nix b/example/simple/flake.nix
index 797e9b35..edc01c5e 100644
--- a/example/simple/flake.nix
+++ b/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 ];
         };
       };
diff --git a/nix/services/default.nix b/nix/services/default.nix
index f3b9dc10..e1861d75 100644
--- a/nix/services/default.nix
+++ b/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
   ];
+
 }
diff --git a/nix/services/devshell.nix b/nix/services/devshell.nix
new file mode 100644
index 00000000..c56aafa5
--- /dev/null
+++ b/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
+      ];
+    };
+  };
+}