add default feature set of some features

If we look at https://xdebug.org/docs/dbgp#options-and-configuration in
the feature names we see any dbgp debugger must provide some feature set
by default. Even if that feature is not actually supported.

So from now on we will set multiple_sessions = 0 because Vdebug does not
support this at the moment and we will try to set extended_properties =
1; if the used debugger does not support it we will silently continue
without the feature.

fixes #369

Signed-off-by: BlackEagle <ike.devolder@gmail.com>

Author: BlackIkeEagle

python3/vdebug/connection.py

@@ -81,7 +81,7 @@ def send_msg(self, cmd):
 
         cmd -- command to send
         """
-        #self.sock.send(cmd + '\0')
+        # self.sock.send(cmd + '\0')
         MSGLEN = len(cmd)
         totalsent = 0
         while totalsent < MSGLEN:

python3/vdebug/session.py

@@ -37,13 +37,14 @@ def listen(self):
             print("Waiting for a connection: none found so far")
         elif self.listener and self.listener.is_ready():
             print("Found connection, starting debugger")
+            log.Log("Got connection, starting", log.Logger.DEBUG)
             self.__new_session()
         else:
             self.start_listener()
 
     def start_listener(self):
         self.listener = listener.Listener.create()
-        print("Vdebug will wait for a connection in the background")
+        print("Vdebug will wait for a connection")
         util.Environment.reload()
         if self.is_open():
             self.ui().set_status("listening")
@@ -103,6 +104,7 @@ def start_if_ready(self):
         try:
             if self.listener.is_ready():
                 print("Found connection, starting debugger")
+                log.Log("Got connection, starting", log.Logger.DEBUG)
                 self.__new_session()
                 return True
             return False
@@ -206,7 +208,9 @@ def start(self, connection):
             self.__ui.set_conn_details(addr[0], addr[1])
 
             self.__collect_context_names()
-            self.__set_features()
+            self.__check_features()  # only for debugging at the moment
+            self.__set_default_features()  # features we try by default
+            self.__set_features()  # user defined features
             self.__initialize_breakpoints()
 
             if opts.Options.get('break_on_open', int) == 1:
@@ -229,6 +233,64 @@ def detach(self):
 
         self.close_connection(False)
 
+    def __check_features(self):
+        must_features = [
+            'language_supports_threads',
+            'language_name',
+            'language_version',
+            'encoding',  # has set
+            'protocol_version',
+            'supports_async',
+            'data_encoding',
+            'breakpoint_languages',
+            'breakpoint_types',
+            'resolved_breakpoints',
+            'multiple_sessions',  # has set
+            'max_children',  # has set
+            'max_data',  # has set
+            'max_depth',  # has set
+            'extended_properties',  # has set
+        ]
+        maybe_features = [
+            'supported_encodings',
+            'supports_postmortem',
+            'show_hidden',  # has set
+            'notify_ok',  # has set
+        ]
+        for feature in must_features:
+            try:
+                feature_value = self.__api.feature_get(feature)
+                log.Log(
+                    "Must Feature: %s = %s" % (feature, str(feature_value)),
+                    log.Logger.DEBUG
+                )
+            except dbgp.DBGPError:
+                error_str = "Failed to get feature %s" % feature
+                log.Log(error_str, log.Logger.DEBUG)
+
+        for feature in maybe_features:
+            try:
+                feature_value = self.__api.feature_get(feature)
+                log.Log(
+                    "Maybe Feature: %s = %s" % (feature, str(feature_value)),
+                    log.Logger.DEBUG
+                )
+            except dbgp.DBGPError:
+                error_str = "Failed to get feature %s" % feature
+                log.Log(error_str, log.Logger.DEBUG)
+
+    def __set_default_features(self):
+        features = {
+            'multiple_sessions': 0,  # explicitly disable multiple sessions atm
+            'extended_properties': 1,
+        }
+        for name, value in features.items():
+            try:
+                self.__api.feature_set(name, value)
+            except dbgp.DBGPError as e:
+                error_str = "Failed to set feature %s: %s" % (name, e.args[0])
+                log.Log(error_str, log.Logger.DEBUG)
+
     def __set_features(self):
         """Evaluate vim dictionary of features and pass to debugger.