Add defaults.processSettings option for shared process configuration (#102)

Author: srid

CHANGELOG.md

@@ -11,6 +11,7 @@
     - #39: Allow `test` process to act as a test, which then gets run as part of flake checks.
     - #55: Add `lib` flake output - library of useful functions
         - #80: Add `evalModules`, to use process-compose-flake without flake-parts
+    - #102: Add `defaults.processSettings` option to set default settings for all processes
     - New options
       - #52: Add `is_foreground` option
       - ~~#54: Add `apiServer` option to control REST API server~~

doc/index.md

@@ -100,6 +100,40 @@ process-compose.watch-server = {
 };
 ```
 
+### Default settings for all processes
+
+You can define default settings that apply to all processes using `defaults.processSettings`. This is useful when you want to set common configuration like namespace, restart behavior, or other settings across all processes.
+
+```nix
+process-compose.watch-server = {
+  defaults.processSettings = { name, ... }: {
+    # Set default namespace for all processes
+    namespace = lib.mkDefault "watch-server";
+    # Set default restart behavior
+    availability.restart = lib.mkDefault "on_failure";
+    availability.max_restarts = lib.mkDefault 3;
+    # Use the process name in log locations
+    log_location = ".logs/${name}.log";
+  };
+
+  settings.processes = {
+    backend-server.command = "...";
+    frontend-server.command = "...";
+    # This process overrides the default namespace
+    proxy-server = {
+      command = "...";
+      namespace = "proxy"; # Overrides the default
+    };
+  };
+};
+```
+
+**Important:** Use `lib.mkDefault` when setting defaults to ensure individual process settings can override them.
+
+You can access the process `name` parameter to create dynamic defaults (e.g., per-process log files).
+
+You can disable defaults entirely by setting `defaults.enable = false`.
+
 ## Module API
 
 Our submodule mirrors the [process-compose YAML schema](https://github.com/F1bonacc1/process-compose/blob/main/process-compose.yaml). A few things to remember:

example/flake.nix

@@ -23,6 +23,11 @@
             dataFile = "data.sqlite";
           in
           {
+            # Default settings for all processes
+            defaults.processSettings = {
+              namespace = lib.mkDefault "sqlite-demo";
+            };
+
             cli = {
               # environment.PC_DISABLE_TUI = true;
               # Global options for `process-compose`

nix/process-compose/default.nix

@@ -6,6 +6,7 @@ in
 {
   imports = [
     ./cli.nix
+    ./defaults.nix
     ./settings
     ./test.nix
   ];

nix/process-compose/defaults.nix

@@ -0,0 +1,43 @@
+# A module representing the default values for all processes in process-compose-flake.
+{ name, lib, config, ... }:
+let
+  inherit (lib)
+    mkOption
+    types;
+in
+{
+  options.defaults = {
+    enable = mkOption {
+      type = types.bool;
+      description = ''
+        Whether to enable default settings for processes in this configuration.
+      '';
+      default = true;
+    };
+
+    processSettings = mkOption {
+      type = types.deferredModule;
+      description = ''
+        Default settings that will be applied to all processes in this configuration.
+
+        Individual process settings can override these defaults. When setting defaults,
+        use `lib.mkDefault` to ensure individual process settings take precedence.
+
+        Example:
+        ```nix
+        defaults.processSettings = {
+          availability.restart = lib.mkDefault "on_failure";
+          availability.max_restarts = lib.mkDefault 3;
+          namespace = lib.mkDefault "myapp";
+        };
+        ```
+      '';
+      apply = settings:
+        if config.defaults.enable then
+          settings
+        else
+          { };
+      default = { };
+    };
+  };
+}

nix/process-compose/settings/default.nix

@@ -10,7 +10,12 @@ in
         modules = [{
           options = {
             processes = mkOption {
-              type = types.attrsOf (types.submoduleWith { modules = [ ./process.nix ]; });
+              type = types.attrsOf (types.submoduleWith {
+                modules = [
+                  ./process.nix
+                  config.defaults.processSettings
+                ];
+              });
               default = { };
               description = ''
                 A map of process names to their configuration.

nix/process-compose/settings/process.nix

@@ -217,7 +217,7 @@ in
       example = true;
       description = ''
         Whether the process is disabled. Useful when a process is required to be started only in a given scenario, like while running in CI.
-        
+
         Even if disabled, the process is still listed in the TUI and the REST client, and can be started manually when needed.
       '';
     };