improve error handling

in the current implementation, in case polling results in an error,
an error_update is generated. But on activate, for this parameter
a normal update will be generated, indicating that this value is ok.

With this change, parameters have an additonal attribue 'readerror',
which save the error generated on the last read, or None, if the
read was successful.

In addition, subsequent repeated errors are only reported the first
time.

Change-Id: I39f18d17debadd8aa5b904e59998d2172f3f11b9
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/21974
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/commandhandler.py

@@ -137,9 +137,10 @@ class ChangeWrapper:
 class CmdHandlerBase:
     """generic command handler"""
 
-    # def __init__(self, group, ...):
-    #     init must at least initialize self.group, which is is relevant for calling the
-    # proper analyze_<group> and change_<group> methods
+    def __init__(self, group):
+        # group is used for calling the proper analyze_<group> and change_<group> methods
+        self.group = group
+        self.parameters = {}
 
     def parse_reply(self, reply):
         """return values from a raw reply"""
@@ -159,7 +160,7 @@ class CmdHandlerBase:
         If changecmd is given, it is prepended before the query.
         """
         querycmd = self.make_query(module)
-        reply = module.sendRecv((changecmd + querycmd))
+        reply = module.sendRecv(changecmd + querycmd)
         return self.parse_reply(reply)
 
     def send_change(self, module, *values):
@@ -173,8 +174,16 @@ class CmdHandlerBase:
         module.sendRecv(changecmd) # ignore result
         return self.send_command(module)
 
-    def get_read_func(self, pname):
-        """returns the read function passed to the metaclass"""
+    def get_read_func(self, modclass, pname):
+        """returns the read function passed to the metaclass
+
+        and registers the parameter in this handler
+        """
+        if not modclass in self.parameters:
+            self.parameters[modclass] = []
+        # Make sure that parameters from different module classes are not mixed
+        # (not sure if this might happen)
+        self.parameters[modclass].append(pname)
         return self.read
 
     def read(self, module):
@@ -182,10 +191,21 @@ class CmdHandlerBase:
 
         overwrite with None if not used
         """
-        # do a read of the current hw values
-        reply = self.send_command(module)
-        # convert them to parameters
-        getattr(module, 'analyze_' + self.group)(*reply)
+        try:
+            # do a read of the current hw values
+            reply = self.send_command(module)
+            # convert them to parameters
+            getattr(module, 'analyze_' + self.group)(*reply)
+            for pname in self.parameters[module.__class__]:
+                if module.parameters[pname].readerror:
+                    # clear errors on parameters, which were not updated.
+                    # this will also inform all activated clients
+                    setattr(module, pname, getattr(module, pname))
+        except Exception as e:
+            # set all parameters of this handler to error
+            for pname in self.parameters[module.__class__]:
+                module.setError(pname, e)
+            raise
         return Done # parameters should be updated already
 
     def get_write_func(self, pname):
@@ -213,7 +233,6 @@ class CmdHandlerBase:
         return wfunc
 
 
-
 class CmdHandler(CmdHandlerBase):
     """more evolved command handler
 
@@ -237,7 +256,7 @@ class CmdHandler(CmdHandlerBase):
         querycmd:  the command for a query, may contain named formats for cmdargs
         replyfmt:  the format for reading the reply with some scanf like behaviour
         """
-        self.group = group
+        super().__init__(group)
         self.querycmd = querycmd
         self.replyfmt = CmdParser(replyfmt)