adds server and client context

src/dls_utilpack/client_context_base.py

@@ -0,0 +1,47 @@
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class ClientContextBase:
+    """
+    Base class for client contexts.
+    Provides some basic commmon housekeeping.
+    """
+
+    # ----------------------------------------------------------------------------------------
+    def __init__(self, specification):
+        self.__specification = specification
+        self.__interface = None
+
+    # ----------------------------------------------------------------------------------------
+    def get_specification(self):
+        return self.__specification
+
+    def set_specification(self, specification):
+        self.__specification = specification
+
+    specification = property(get_specification, set_specification)
+
+    # ----------------------------------------------------------------------------------------
+    def get_interface(self):
+        return self.__interface
+
+    def set_interface(self, interface):
+        self.__interface = interface
+
+    interface = property(get_interface, set_interface)
+
+    # ----------------------------------------------------------------------------------------
+    async def __aenter__(self):
+        """ """
+
+        await self.aenter()
+
+        return self.interface
+
+    # ----------------------------------------------------------------------------------------
+    async def __aexit__(self, type, value, traceback):
+        """ """
+
+        await self.aexit()

src/dls_utilpack/server_context_base.py

@@ -0,0 +1,84 @@
+import logging
+
+# Utilities.
+from dls_utilpack.callsign import callsign
+
+# Base class for a Thing which has a name and traits.
+from dls_utilpack.thing import Thing
+
+logger = logging.getLogger(__name__)
+
+
+class ServerContextBase(Thing):
+    """
+    Base class for an "async with" context which can be wrapped around a server object.
+
+    Contains convenience methods common to all server contexts.
+
+    The server object reference is supplied to this object externally.
+
+    The server object must provide the follwing methods:
+        - is_process_started()
+        - is_process_alive()
+
+    """
+
+    # ----------------------------------------------------------------------------------------
+    def __init__(
+        self,
+        thing_type,
+        specification=None,
+        predefined_uuid=None,
+    ):
+        Thing.__init__(
+            self,
+            thing_type,
+            specification,
+            predefined_uuid=predefined_uuid,
+        )
+
+        # Reference to object which is a server, such as BaseAiohttp.
+        self.server = None
+
+        # The context specification of the server's specification.
+        self.context_specification = self.specification().get("context", {})
+
+    # ----------------------------------------------------------------------------------------
+    async def is_process_started(self):
+        """"""
+
+        if self.server is None:
+            raise RuntimeError(f"{callsign(self)} a process has not been defined")
+
+        try:
+            return await self.server.is_process_started()
+        except Exception:
+            raise RuntimeError(
+                f"unable to determing process started for server {callsign(self.server)}"
+            )
+
+    # ----------------------------------------------------------------------------------------
+    async def is_process_alive(self):
+        """"""
+
+        if self.server is None:
+            raise RuntimeError(f"{callsign(self)} a process has not been defined")
+
+        try:
+            return await self.server.is_process_alive()
+        except Exception:
+            raise RuntimeError(
+                f"unable to determing dead or alive for server {callsign(self.server)}"
+            )
+
+    # ----------------------------------------------------------------------------------------
+    async def __aenter__(self):
+        """ """
+
+        await self.aenter()
+
+    # ----------------------------------------------------------------------------------------
+    async def __aexit__(self, type, value, traceback):
+        """ """
+
+        await self.aexit(type, value, traceback)

src/dls_utilpack/thing.py

@@ -17,7 +17,12 @@ class Thing:
 
     def __init__(self, thing_type: str, specification, predefined_uuid=None):
         self.__thing_type = thing_type
-        self.__specification = specification
+
+        if specification is None:
+            self.__specification = {}
+        else:
+            self.__specification = specification
+
         self.__uuid = predefined_uuid
         if self.__uuid is None:
             self.__uuid = str(uuid.uuid4())

tests/test_server_context.py

@@ -0,0 +1,70 @@
+import logging
+
+from dls_utilpack.server_context_base import ServerContextBase
+
+# Base class for the tester.
+from tests.base_tester import BaseTester
+
+logger = logging.getLogger(__name__)
+
+
+class Server:
+    # Minimal methods required for a "server" to provide.
+    async def is_process_alive(self):
+        return True
+
+    async def is_process_started(self):
+        return True
+
+
+class Context(ServerContextBase):
+    # For testing.
+    def __init__(self, thing_type, specification=None, predefined_uuid=None):
+        ServerContextBase.__init__(
+            self,
+            thing_type,
+            specification=specification,
+            predefined_uuid=predefined_uuid,
+        )
+
+        self.was_entered = 0
+        self.was_exited = 0
+
+    # Minimal methods required for a "context" to provide.
+    async def aenter(self):
+        """ """
+        self.was_entered += 1
+
+    async def aexit(self, type, value, traceback):
+        """ """
+        self.was_exited += 1
+
+
+# ----------------------------------------------------------------------------------------
+class TestServerContext(BaseTester):
+    def test(self, constants, logging_setup, output_directory):
+        """ """
+
+        self.main(constants, output_directory)
+
+    # ----------------------------------------------------------------------------------------
+    async def _main_coroutine(
+        self,
+        constants,
+        output_directory,
+    ):
+        """ """
+
+        # Make the context.
+        context = Context("some::thing")
+
+        # Assign the server.
+        context.server = Server()
+
+        # Run the context.
+        async with context:
+            assert await context.is_process_started()
+            assert await context.is_process_alive()
+
+        assert context.was_entered == 1
+        assert context.was_exited == 1