fix(DeploymentNode): children should inherit environment from parent

src/structurizr/model/deployment_node.py

@@ -27,6 +27,7 @@
 from .relationship import Relationship
 from .software_system import SoftwareSystem
 from .software_system_instance import SoftwareSystemInstance, SoftwareSystemInstanceIO
+from .tags import Tags
 
 
 if TYPE_CHECKING:  # pragma: no cover
@@ -114,6 +115,7 @@ def __init__(
         self._container_instances = set(container_instances)
         self._software_system_instances = set(software_system_instances)
         self._infrastructure_nodes = set(infrastructure_nodes)
+        self.tags.add(Tags.DEPLOYMENT_NODE)
 
     @property
     def children(self) -> Iterable["DeploymentNode"]:
@@ -158,7 +160,11 @@ def add_deployment_node(
             **kwargs: additional keyword arguments for instantiating a `DeploymentNode`
         """
         node = DeploymentNode(
-            name=name, description=description, technology=technology, **kwargs
+            name=name,
+            description=description,
+            technology=technology,
+            environment=self.environment,
+            **kwargs,
         )
         self._add_child_deployment_node(node)
         return node
@@ -296,6 +302,13 @@ def _add_child_deployment_node(self, node: "DeploymentNode"):
                 f"DeploymentNode with name '{node.name}' already has parent "
                 f"{node.parent}. Cannot add to {self}."
             )
+
+        if node.environment != self.environment:
+            raise ValueError(
+                f"DeploymentNode {node.name} cannot be in a different environment "
+                f"({node.environment}) from its parent ({self.environment})."
+            )
+
         self._children.add(node)
         if self.has_model:
             model = self.model

tests/unit/model/test_deployment_node.py

@@ -19,6 +19,7 @@
 from structurizr.model import Container, Relationship, SoftwareSystem
 from structurizr.model.deployment_node import DeploymentNode, DeploymentNodeIO
 from structurizr.model.infrastructure_node import InfrastructureNode
+from structurizr.model.tags import Tags
 
 
 class MockModel:
@@ -78,6 +79,7 @@ def test_deployment_node_init(attributes):
     node = DeploymentNode(**attributes)
     for attr, expected in attributes.items():
         assert getattr(node, attr) == expected
+    assert Tags.DEPLOYMENT_NODE in node.tags
 
 
 def test_deployment_node_adds_to_children(model_with_node):
@@ -99,6 +101,25 @@ def test_deployment_node_adding_same_child_twice_is_ok(model_with_node):
     assert len(top_node.children) == 1
 
 
+def test_deployment_node_child_picks_up_environment(model_with_node):
+    """Ensure that the environment of the child matches the parent."""
+    top_node = model_with_node.empty_node
+    child = top_node.add_deployment_node(name="child")
+    assert child.environment == "Live"
+
+
+def test_deployment_node_cant_add_child_in_different_environment(model_with_node):
+    """Ensure that the environment of the child matches the parent."""
+    top_node = model_with_node.empty_node
+    child = DeploymentNode(name="child", environment="Dev")
+    with pytest.raises(
+        ValueError,
+        match=r"DeploymentNode .* cannot be in a different environment \(Dev\) from "
+        + r"its parent \(Live\)\.",
+    ):
+        top_node += child
+
+
 def test_deployment_node_add_child_with_existing_parent(model_with_node: MockModel):
     """Check that adding a node with an existing parent fails."""
     top_node = model_with_node.empty_node
@@ -156,7 +177,7 @@ def test_deployment_node_add_with_iadd(model_with_node: MockModel):
     model_with_node += system
     container = Container(name="container")
     system += container
-    child_node = DeploymentNode(name="child")
+    child_node = DeploymentNode(name="child", environment="Live")
     infra_node = InfrastructureNode(name="infra")
 
     node += child_node