Make database file optional for EpicsAdapter

src/tickit/adapters/epicsadapter/adapter.py

@@ -3,7 +3,7 @@
 from abc import abstractmethod
 from dataclasses import dataclass
 from tempfile import NamedTemporaryFile
-from typing import Any, Callable, Dict
+from typing import Any, Callable, Dict, Optional
 
 from softioc import builder, softioc
 
@@ -30,14 +30,18 @@ class OutputRecord:
 
 
 class EpicsAdapter(Adapter):
-    """An adapter implementation which acts as an EPICS IOC."""
+    """An adapter implementation which acts as an EPICS IOC.
 
-    def __init__(self, db_file: str, ioc_name: str) -> None:
+    This is optionally initialised from an EPICS database (db) file
+    but can be customised in code by implementing on_db_load.
+    """
+
+    def __init__(self, ioc_name: str, db_file: Optional[str] = None) -> None:
         """An EpicsAdapter constructor which stores the db_file path and the IOC name.
 
         Args:
-            db_file (str): The path to the db_file.
             ioc_name (str): The name of the EPICS IOC.
+            db_file (str, optional): The path to the db_file.
         """
         self.db_file = db_file
         self.ioc_name = ioc_name
@@ -68,7 +72,7 @@ def on_db_load(self) -> None:
         raise NotImplementedError
 
     def load_records_without_DTYP_fields(self):
-        """Loads the records without DTYP fields."""
+        """Load records from database file without DTYP fields."""
         with open(self.db_file, "rb") as inp:
             with NamedTemporaryFile(suffix=".db", delete=False) as out:
                 for line in inp.readlines():
@@ -84,7 +88,8 @@ async def run_forever(
         """Runs the server continuously."""
         await super().run_forever(device, raise_interrupt)
         builder.SetDeviceName(self.ioc_name)
-        self.load_records_without_DTYP_fields()
+        if self.db_file:
+            self.load_records_without_DTYP_fields()
         self.on_db_load()
         builder.UnsetDevice()
         notify_adapter_ready(self.ioc_num)

tests/adapters/test_epicsadapter/test_epics_adapter.py

@@ -4,7 +4,7 @@
 from mock import MagicMock, Mock, create_autospec, mock_open, patch
 
 from tickit.adapters.epicsadapter import EpicsAdapter, InputRecord
-from tickit.core.adapter import Adapter, Interpreter
+from tickit.core.adapter import Adapter, Interpreter, RaiseInterrupt
 from tickit.core.device import Device
 
 
@@ -20,7 +20,12 @@ def MockInterpreter() -> Mock:
 
 @pytest.fixture
 def epics_adapter() -> EpicsAdapter:
-    return EpicsAdapter("db_file", "ioc_name")  # type: ignore
+    return EpicsAdapter("ioc_name", db_file="db_file")  # type: ignore
+
+
+@pytest.fixture
+def adapter_no_db_file() -> EpicsAdapter:
+    return EpicsAdapter("ioc_name")  # type: ignore
 
 
 @pytest.fixture
@@ -34,6 +39,14 @@ def getter():
     return InputRecord("input", Mock(setter), Mock(getter))
 
 
+@pytest.fixture
+def mock_raise_interrupt():
+    async def raise_interrupt():
+        return False
+
+    return Mock(raise_interrupt)
+
+
 def test_epics_adapter_is_adapter():
     assert issubclass(EpicsAdapter, Adapter)
 
@@ -139,3 +152,31 @@ def test_epics_adapter_load_records_without_DTYP_fields_method(
         written_data = file.read()
 
     assert str(written_data).strip() == str(test_params["expected"]).strip()
+
+
+@pytest.mark.asyncio
+async def test_db_file_not_specified(
+    adapter_no_db_file: EpicsAdapter,
+    MockDevice: Device,
+    mock_raise_interrupt: RaiseInterrupt,
+):
+    adapter_no_db_file.on_db_load = MagicMock()  # type: ignore
+    adapter_no_db_file.load_records_without_DTYP_fields = MagicMock()  # type: ignore
+
+    await adapter_no_db_file.run_forever(MockDevice, mock_raise_interrupt)
+
+    adapter_no_db_file.load_records_without_DTYP_fields.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_db_load_called_if_file_specified(
+    epics_adapter: EpicsAdapter,
+    MockDevice: Device,
+    mock_raise_interrupt: RaiseInterrupt,
+):
+    epics_adapter.on_db_load = MagicMock()  # type: ignore
+    epics_adapter.load_records_without_DTYP_fields = MagicMock()  # type: ignore
+
+    await epics_adapter.run_forever(MockDevice, mock_raise_interrupt)
+
+    epics_adapter.load_records_without_DTYP_fields.assert_called_once()