Replay stored fields into the Case class on controller initialisation…

data-serving/reusable-data-service/data_service/controller/schema_controller.py

@@ -10,8 +10,16 @@ class SchemaController:
 
     def __init__(self, store):
         self.store = store
+        self.restore_saved_fields()
 
-    def add_field(self, name: str, type_name: str, description: str):
+    def restore_saved_fields(self) -> None:
+        """Find previously-created fields in the store and apply them."""
+        for field in self.store.get_case_fields():
+            self.add_field(field.key, field.type, field.data_dictionary_text, False)
+
+    def add_field(
+        self, name: str, type_name: str, description: str, store_field: bool = True
+    ):
         global Case
         """Add a field of the specified type to the Case class. There cannot
         already be a field of that name, either built in, as part of the
@@ -20,7 +28,10 @@ def add_field(self, name: str, type_name: str, description: str):
         Additionally dataclasses imposes other conditions (for example names
         cannot be Python keywords).
 
-        The description will be used in the data dictionary."""
+        The description will be used in the data dictionary.
+
+        Fields will by default be added to the store. Set store_field to False if this is not
+        necessary, for example if the field to be added is coming from the store."""
         existing_fields = dataclasses.fields(Case)
         if name in [f.name for f in existing_fields]:
             raise ConflictError(f"field {name} already exists")
@@ -33,7 +44,8 @@ def add_field(self, name: str, type_name: str, description: str):
         fields_list.append((name, type, dataclasses.field(init=False, default=None)))
         # re-invent the Case class
         Case = make_custom_case_class("Case", fields_list)
-        # create a storable model of the field and store it
-        # FIXME rewrite the validation logic above to use the data model
-        field_model = Field(name, type_name, description)
-        self.store.add_field(field_model)
+        if store_field:
+            # create a storable model of the field and store it
+            # FIXME rewrite the validation logic above to use the data model
+            field_model = Field(name, type_name, description)
+            self.store.add_field(field_model)

data-serving/reusable-data-service/data_service/stores/mongo_store.py

@@ -228,6 +228,12 @@ def case_exclusion_to_bson_compatible_dict(exclusion: CaseExclusionMetadata):
     def add_field(self, field: Field):
         self.get_schema_collection().insert_one(field.to_dict())
 
+    def get_case_fields(self):
+        return [
+            Field(doc["key"], doc["type"], doc["data_dictionary_text"])
+            for doc in self.get_schema_collection().find({})
+        ]
+
 
 def date_to_datetime(dt: datetime.date) -> datetime.datetime:
     """Convert datetime.date to datetime.datetime for encoding as BSON"""

data-serving/reusable-data-service/tests/test_schema_controller_field_changes.py

@@ -1,3 +1,4 @@
+import datetime
 import pytest
 
 from data_service.controller.schema_controller import SchemaController
@@ -23,11 +24,16 @@ def case_observer(case_class: type) -> None:
 
 
 @pytest.fixture
-def schema_controller():
-    store = MemoryStore()
+def observing_case_changes():
     observe_case_class(case_observer)
-    yield SchemaController(store)
+    yield
     remove_case_class_observer(case_observer)
+
+
+@pytest.fixture
+def schema_controller(observing_case_changes):
+    store = MemoryStore()
+    yield SchemaController(store)
     reset_custom_case_fields()
 
 
@@ -70,3 +76,14 @@ def test_added_field_gets_stored(schema_controller):
     assert (
         field.data_dictionary_text == "A string that describes some feature of a case."
     )
+
+
+def test_stored_field_gets_added(observing_case_changes):
+    store_with_preexisting_field = MemoryStore()
+    a_field = Field(
+        "outcome_date", Field.DATE, "The date on which the case reached an outcome."
+    )
+    store_with_preexisting_field.add_field(a_field)
+    controller = SchemaController(store_with_preexisting_field)
+    assert "outcome_date" in Case.field_names()
+    assert Case.field_type("outcome_date") is datetime.date