add init nodes that are called before channel subhandle

pypeman/channels.py

@@ -79,6 +79,7 @@ def __init__(self, name=None, parent_channel=None, loop=None, message_store_fact
         self.drop_nodes = None
         self.reject_nodes = None
         self.final_nodes = None
+        self.init_nodes = None
         self.wait_subchans = wait_subchans
         self.raise_dropped = False
 
@@ -375,6 +376,8 @@ async def handle(self, msg):
         async with self.lock:
             self.status = BaseChannel.PROCESSING
             try:
+                if self.init_nodes:
+                    msg = await self.init_nodes[0].handle(msg.copy())
                 result = await self.subhandle(msg.copy())
                 await self.message_store.change_message_state(msg_store_id, message.Message.PROCESSED)
                 msg.chan_rslt = result
@@ -593,6 +596,15 @@ def _init_end_nodes(self, *end_nodes):
                 previous_node = node
         return end_nodes
 
+    def add_init_nodes(self, *nodes):
+        """
+        Add nodes that will be launched at the start of the channel before all
+        processing nodes
+        """
+        if self.init_nodes:
+            nodes = self.init_nodes.extend(nodes)
+        self.init_nodes = self._init_end_nodes(*nodes)
+
     def add_join_nodes(self, *end_nodes):
         """
         Add nodes that will be launched only after a successful channel process

pypeman/nodes.py

@@ -168,7 +168,6 @@ async def handle(self, msg):
             result = await self.async_run(msg)
         else:
             result = self.run(msg)
-
         self.processed += 1
 
         if isinstance(result, asyncio.Future):

pypeman/tests/test_channel.py

@@ -4,6 +4,8 @@
 import tempfile
 import time
 
+from functools import partial
+
 from hl7.client import MLLPClient
 
 from pathlib import Path
@@ -39,6 +41,11 @@ def raise_exc(msg):
     raise Exception()
 
 
+def return_text(msg, text="toto"):
+    msg.payload = text
+    return msg
+
+
 class ChannelsTests(TestCase):
     def clean_loop(self):
         # Useful to execute future callbacks  # TODO: remove ?
@@ -234,6 +241,28 @@ def test_final_nodes(self):
             vars(self.clean_msg(msg1)), vars(self.clean_msg(endnode_input)),
             "Channel final_nodes don't takes event msg in input")
 
+    def test_init_nodes(self):
+        """ Whether BaseChannel init_nodes is working """
+        chan1 = BaseChannel(name="test_channel_init_clbk", loop=self.loop)
+        initouttext = "tutu"
+
+        n1 = TstNode(name="n1")
+        initnode = TstNode(name="initnode")
+        n1._reset_test()
+        initnode._reset_test()
+        initnode.mock(output=partial(return_text, text=initouttext))
+        chan1.add_init_nodes(initnode)
+        chan1.add(n1)
+        msg1 = generate_msg(message_content="startmsg")
+        self.start_channels()
+
+        self.loop.run_until_complete(chan1.handle(msg1))
+
+        n1_input = n1.last_input()
+        self.assertEqual(
+            n1_input.payload, initouttext,
+            "Channel init_nodes doesn't seems to work")
+
     def test_multiple_callbacks(self):
         """
             Whether BaseChannel all endnodes are working at same time