Basic usage of devShell

[peedrr]

TL;DR: Is it always necessary to nix run before opening a dev shell?

Firstly, thank you! My stack is Postgres, Redis and Nats, so it looks like I'm well covered straight out of the box.

I'm right at the beginning of my journey with services-flake so please excuse the "page 1" question! (And I'm only on about page 2 with flakes!)

The flake gets loaded by direnv

Here's my flake so far:

{
  description = "Testing services-flake with Redis";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

    # services-flake
    process-compose-flake.url = "github:Platonic-Systems/process-compose-flake";
    services-flake.url = "github:juspay/services-flake";
    flake-parts.url = "github:hercules-ci/flake-parts";
  };

  outputs = inputs:
    inputs.flake-parts.lib.mkFlake { inherit inputs; } {
      imports = [
        # import the flake module
        inputs.process-compose-flake.flakeModule
      ];
      systems = inputs.nixpkgs.lib.systems.flakeExposed;
      perSystem = { pkgs, config, ... }: {
        # Create the process-compose configuration, importing services-flake
        process-compose."default" = {
          imports = [
            inputs.services-flake.processComposeModules.default
          ];
          # Define the services to be started
          services = {
            redis."r1".enable = true;
          };
        };

        # DevShell
        devShells.default = pkgs.mkShell {
          inputsFrom = [
            config.process-compose."default".services.outputs.devShell
          ];
        };
      };
    };
}

When I cd into the directory I seem to already have packages, e.g. redis-cli, but redis-server is not running:

$ redis-cli
Could not connect to Redis at 127.0.0.1:6379: Connection refused
not connected>

Obviously nix run then gives me Process Compose. Opening another shell to the same directory then allows me to connect to the Redis server. Is this the intended usage? Is it possible to nix develop and then start Process Compose as needed? (Without typing nix run?)

[peedrr]

I'm going to close this. I've only just found out the direnv makes nix develop redundant as I'm already in a "dev shell"! So nix run is the way to manually start Process Compose!!

Every day is a school day!