[BUGFIX] set_operation_model ordering with layout (#867)

* Handling for order of set_operation model and setting layout.

* ruff.

* One more test added.

floris/core/farm.py

@@ -209,7 +209,8 @@ def check_turbine_type(self, attribute: attrs.Attribute, value: Any) -> None:
         if len(value) != 1 and len(value) != self.n_turbines:
             raise ValueError(
                 "turbine_type must have the same number of entries as layout_x/layout_y or have "
-                "a single turbine_type value."
+                "a single turbine_type value. This error can arise if you set the turbine_type or "
+                "alter the operation model before setting the layout."
             )
 
     @turbine_library_path.validator

floris/floris_model.py

@@ -1451,13 +1451,23 @@ def set_operation_model(self, operation_model: str | List[str]):
             operation_model (str): The operation model to set.
         """
         if isinstance(operation_model, str):
-            operation_model = [operation_model]*self.core.farm.n_turbines
-        elif len(operation_model) != self.core.farm.n_turbines:
+            if len(self.core.farm.turbine_type) == 1:
+                # Set a single one here, then, and return
+                turbine_type = self.core.farm.turbine_definitions[0]
+                turbine_type["operation_model"] = operation_model
+                self.set(turbine_type=[turbine_type])
+                return
+            else:
+                operation_model = [operation_model]*self.core.farm.n_turbines
+
+        if len(operation_model) != self.core.farm.n_turbines:
             raise ValueError(
-                "The length of the operation_model list must be equal to the number of turbines."
-            )
+                    "The length of the operation_model list must be "
+                    "equal to the number of turbines."
+                )
 
         turbine_type_list = self.core.farm.turbine_definitions
+
         for tindex in range(self.core.farm.n_turbines):
             turbine_type_list[tindex]["turbine_type"] = (
                 turbine_type_list[tindex]["turbine_type"]+"_"+operation_model[tindex]

tests/floris_model_integration_test.py

@@ -647,3 +647,38 @@ def test_set_operation_model():
     fmodel.set(layout_x=[0, 0], layout_y=[0, 1000])
     fmodel.set_operation_model(["simple-derating", "cosine-loss"])
     assert fmodel.get_operation_model() == ["simple-derating", "cosine-loss"]
+
+    # Check that setting a single turbine type, and then altering the operation model works
+    fmodel.set(layout_x=[0, 0], layout_y=[0, 1000])
+    fmodel.set(turbine_type=["nrel_5MW"])
+    fmodel.set_operation_model("simple-derating")
+    assert fmodel.get_operation_model() == "simple-derating"
+
+    # Check that setting over mutliple turbine types works
+    fmodel.set(turbine_type=["nrel_5MW", "iea_15MW"])
+    fmodel.set_operation_model("simple-derating")
+    assert fmodel.get_operation_model() == "simple-derating"
+    fmodel.set_operation_model(["simple-derating", "cosine-loss"])
+    assert fmodel.get_operation_model() == ["simple-derating", "cosine-loss"]
+
+    # Check setting over single turbine type; then updating layout works
+    fmodel.set(turbine_type=["nrel_5MW"])
+    fmodel.set_operation_model("simple-derating")
+    fmodel.set(layout_x=[0, 0, 0], layout_y=[0, 1000, 2000])
+    assert fmodel.get_operation_model() == "simple-derating"
+
+    # Check that setting for multiple turbine types and then updating layout breaks
+    fmodel.set(layout_x=[0, 0], layout_y=[0, 1000])
+    fmodel.set(turbine_type=["nrel_5MW"])
+    fmodel.set_operation_model(["simple-derating", "cosine-loss"])
+    assert fmodel.get_operation_model() == ["simple-derating", "cosine-loss"]
+    with pytest.raises(ValueError):
+        fmodel.set(layout_x=[0, 0, 0], layout_y=[0, 1000, 2000])
+
+    # Check one more variation
+    fmodel.set(layout_x=[0, 0], layout_y=[0, 1000])
+    fmodel.set(turbine_type=["nrel_5MW", "iea_15MW"])
+    fmodel.set_operation_model("simple-derating")
+    fmodel.set(layout_x=[0, 0], layout_y=[0, 1000])
+    with pytest.raises(ValueError):
+        fmodel.set(layout_x=[0, 0, 0], layout_y=[0, 1000, 2000])