refactor: move model lookups out of instance hyrdation and into DeploymentNode

Author: yt-ms

src/structurizr/model/container_instance.py

@@ -30,7 +30,6 @@
 
 if TYPE_CHECKING:  # pragma: no cover
     from .deployment_node import DeploymentNode
-    from .model import Model
 
 
 __all__ = ("ContainerInstance", "ContainerInstanceIO")
@@ -64,18 +63,16 @@ def container_id(self) -> str:
     def hydrate(
         cls,
         container_instance_io: ContainerInstanceIO,
-        model: "Model",
+        container: Container,
         parent: "DeploymentNode",
     ) -> "ContainerInstance":
         """Hydrate a new ContainerInstance instance from its IO.
 
         This will also automatically register with the model.
         """
-        container = model.get_element(container_instance_io.container_id)
         instance = cls(
             **cls.hydrate_arguments(container_instance_io),
             container=container,
             parent=parent,
         )
-        model += instance
         return instance

src/structurizr/model/deployment_node.py

@@ -302,12 +302,16 @@ def hydrate(
             node += child_node
 
         for instance_io in deployment_node_io.container_instances:
-            instance = ContainerInstance.hydrate(instance_io, model=model, parent=node)
+            container = model.get_element(instance_io.container_id)
+            instance = ContainerInstance.hydrate(
+                instance_io, container=container, parent=node
+            )
             node._container_instances.add(instance)
 
         for instance_io in deployment_node_io.software_system_instances:
+            system = model.get_element(instance_io.software_system_id)
             instance = SoftwareSystemInstance.hydrate(
-                instance_io, model=model, parent=node
+                instance_io, system=system, parent=node
             )
             node._software_system_instances.add(instance)
 

src/structurizr/model/software_system_instance.py

@@ -30,7 +30,6 @@
 
 if TYPE_CHECKING:  # pragma: no cover
     from .deployment_node import DeploymentNode
-    from .model import Model
 
 
 __all__ = ("SoftwareSystemInstance", "SoftwareSystemInstanceIO")
@@ -64,11 +63,10 @@ def software_system_id(self) -> str:
     def hydrate(
         cls,
         system_instance_io: SoftwareSystemInstanceIO,
-        model: "Model",
+        system: SoftwareSystem,
         parent: "DeploymentNode",
     ) -> "SoftwareSystemInstance":
         """Hydrate a new SoftwareSystemInstance instance from its IO."""
-        system = model.get_element(system_instance_io.software_system_id)
         instance = cls(
             **cls.hydrate_arguments(system_instance_io),
             software_system=system,

tests/unit/model/test_container_instance.py

@@ -83,23 +83,13 @@ def test_container_instance_tags(model_with_container):
     assert Tags.CONTAINER_INSTANCE in instance.tags
 
 
-def test_container_instance_hydration_retrieves_container_from_id(model_with_container):
-    """Check that the container instance is retrieved from the model on hydration."""
-    io = ContainerInstanceIO(container_id="19", instance_id=3, environment="Live")
-
-    instance = ContainerInstance.hydrate(io, model_with_container, parent=None)
-
-    assert instance.instance_id == 3
-    assert instance.environment == "Live"
-    assert instance.container is model_with_container.mock_container
-    assert instance.container_id == "19"
-
-
 def test_container_instance_name_is_container_name(model_with_container):
     """Ensure container instance takes its name from its container."""
     io = ContainerInstanceIO(container_id="19", instance_id=3, environment="Live")
 
-    instance = ContainerInstance.hydrate(io, model_with_container, parent=None)
+    instance = ContainerInstance.hydrate(
+        io, model_with_container.mock_container, parent=None
+    )
 
     assert instance.name == "Mock Container"
 
@@ -114,7 +104,9 @@ def test_container_instance_hyrdates_http_health_checks(model_with_container):
         health_checks=[health_check_io],
     )
 
-    instance = ContainerInstance.hydrate(io, model_with_container, parent=None)
+    instance = ContainerInstance.hydrate(
+        io, model_with_container.mock_container, parent=None
+    )
 
     assert len(instance.health_checks) == 1
     assert list(instance.health_checks)[0].name == "name"

tests/unit/model/test_model.py

@@ -165,6 +165,13 @@ def test_model_get_software_system_bad_id(empty_model: Model):
     assert empty_model.get_software_system_with_id(container.id) is None
 
 
+def test_model_add_element_twice_is_ignored(empty_model: Model):
+    """Test you can't add an element with the same ID as an existing one."""
+    system1 = empty_model.add_software_system(name="System")
+    empty_model += system1
+    assert empty_model.software_systems == {system1}
+
+
 def test_model_add_element_with_existing_id_raises_error(empty_model: Model):
     """Test you can't add an element with the same ID as an existing one."""
     system1 = empty_model.add_software_system(name="System")

tests/unit/model/test_software_system_instance.py

@@ -86,29 +86,15 @@ def test_software_system_instance_tags(model_with_system):
     assert Tags.SOFTWARE_SYSTEM_INSTANCE in node.tags
 
 
-def test_software_system_instance_hydration_retrieves_software_system_from_id(
-    model_with_system,
-):
-    """Check that the software_system instance is retrieved on hydration."""
-    io = SoftwareSystemInstanceIO(
-        software_system_id="19", instance_id=3, environment="Live"
-    )
-
-    instance = SoftwareSystemInstance.hydrate(io, model_with_system, parent=None)
-
-    assert instance.instance_id == 3
-    assert instance.environment == "Live"
-    assert instance.software_system is model_with_system.mock_system
-    assert instance.software_system_id == "19"
-
-
 def test_software_system_instance_name_is_software_system_name(model_with_system):
     """Ensure software_system instance takes its name from its software system."""
     io = SoftwareSystemInstanceIO(
         software_system_id="19", instance_id=3, environment="Live"
     )
 
-    instance = SoftwareSystemInstance.hydrate(io, model_with_system, parent=None)
+    instance = SoftwareSystemInstance.hydrate(
+        io, model_with_system.mock_system, parent=None
+    )
 
     assert instance.name == "Mock System"
 
@@ -123,7 +109,9 @@ def test_software_system_instance_hyrdates_http_health_checks(model_with_system)
         health_checks=[health_check_io],
     )
 
-    instance = SoftwareSystemInstance.hydrate(io, model_with_system, parent=None)
+    instance = SoftwareSystemInstance.hydrate(
+        io, model_with_system.mock_system, parent=None
+    )
 
     assert len(instance.health_checks) == 1
     assert list(instance.health_checks)[0].name == "name"