Add default network with name = project.name

docs/modules/ROOT/partials/NixOSOptions.adoc

@@ -22,6 +22,30 @@ Attribute set that will be turned into the docker-compose.yaml file, using Nix's
 Type:: attribute set
 No Default:: {blank}
 
+No Example:: {blank}
+
+== enableDefaultNetwork
+
+Whether to define the default network:
+
+```nix
+networks.default = {
+  name = config.project.name;
+};
+```
+
+
+[discrete]
+=== details
+
+Type:: boolean
+Default::
++
+----
+true
+----
+
+
 No Example:: {blank}
 
 == host.nixStorePrefix
@@ -79,12 +103,7 @@ See link:https://docs.docker.com/compose/compose-file/#networks-top-level-elemen
 === details
 
 Type:: lazy attribute set of submodules
-Default::
-+
-----
-{}
-----
-
+No Default:: {blank}
 
 No Example:: {blank}
 

src/haskell/testdata/Arion/NixSpec/arion-compose.json

@@ -1,5 +1,9 @@
 {
-    "networks": {},
+    "networks": {
+        "default": {
+            "name": "unit-test-data"
+        }
+    },
     "services": {
         "webserver": {
             "command": [

src/nix/modules/composition/networks.nix

@@ -21,13 +21,31 @@ in
       description = ''
         ${dockerComposeRef "networks-top-level-element"}
       '';
-      default = {};
+    };
+    enableDefaultNetwork = mkOption {
+      type = types.bool;
+      description = ''
+        Whether to define the default network:
+
+        ```nix
+        networks.default = {
+          name = config.project.name;
+        };
+        ```
+      '';
+      default = true;
     };
   };
 
 
   config = {
 
+    networks = optionalAttrs config.enableDefaultNetwork {
+      default = {
+        name = config.project.name;
+      };
+    };
+
     docker-compose.raw.networks =
       lib.mapAttrs (k: v: v.out) config.networks;