Make setting ansible_network_os optional for network_cli and netconf

*  Add `load_platform_plugins` method in network_cli and netconf
   connection to handle loading of sub-plugins when either invoked
   by setting `ansible_network_os` value of by calling it from
   the module code.

changelogs/fragments/network_os_optional_network_cli_netconf.yaml

@@ -0,0 +1,3 @@
+---
+minor_changes:
+  - Make ansible_network_os as optional param for network_cli and netconf connection plugins.

plugins/connection/netconf.py

@@ -154,6 +154,13 @@
     - name: ANSIBLE_NETCONF_SSH_CONFIG
     vars:
     - name: ansible_netconf_ssh_config
+  platform_type:
+    description:
+    - Set type of platform.
+    env:
+    - name: ANSIBLE_PLATFORM_TYPE
+    vars:
+    - name: ansible_platform_type
 """
 
 import os
@@ -207,12 +214,20 @@ def __init__(self, play_context, new_stdin, *args, **kwargs):
         super(Connection, self).__init__(
             play_context, new_stdin, *args, **kwargs
         )
+        self._manager = None
+        self.key_filename = None
+        self._ssh_config = None
+        self._platform_type = None
+        self.load_platform_plugins(self._network_os)
 
-        # If network_os is not specified then set the network os to auto
+    def load_platform_plugins(self, platform_type=None):
+        # If network_os/platform_type is not specified then set the network os to auto
         # This will be used to trigger the use of guess_network_os when connecting.
-        self._network_os = self._network_os or "auto"
+        platform_type = (
+            platform_type or self.get_option("platform_type") or "auto"
+        )
 
-        self.netconf = netconf_loader.get(self._network_os, self)
+        self.netconf = netconf_loader.get(platform_type, self)
         if self.netconf:
             self._sub_plugin = {
                 "type": "netconf",
@@ -225,7 +240,7 @@ def __init__(self, play_context, new_stdin, *args, **kwargs):
                 % (
                     self.netconf._load_name,
                     self.netconf._original_path,
-                    self._network_os,
+                    platform_type,
                 ),
             )
         else:
@@ -238,13 +253,11 @@ def __init__(self, play_context, new_stdin, *args, **kwargs):
             self.queue_message(
                 "vvvv",
                 "unable to load netconf plugin for network_os %s, falling back to default plugin"
-                % self._network_os,
+                % platform_type,
             )
 
-        self.queue_message("log", "network_os is set to %s" % self._network_os)
-        self._manager = None
-        self.key_filename = None
-        self._ssh_config = None
+        self.queue_message("log", "network_os is set to %s" % platform_type)
+        self._network_os = platform_type
 
     def exec_command(self, cmd, in_data=None, sudoable=True):
         """Sends the request to the node and returns the reply

plugins/connection/network_cli.py

@@ -274,6 +274,13 @@
     - name: ANSIBLE_NETWORK_SINGLE_USER_MODE
     vars:
     - name: ansible_network_single_user_mode
+  platform_type:
+    description:
+    - Set type of platform.
+    env:
+    - name: ANSIBLE_PLATFORM_TYPE
+    vars:
+    - name: ansible_platform_type
 """
 
 from functools import wraps
@@ -362,13 +369,29 @@ def __init__(self, play_context, new_stdin, *args, **kwargs):
         self._single_user_mode = False
 
         if self._network_os:
-            self._terminal = terminal_loader.get(self._network_os, self)
+            self.load_platform_plugins(self._network_os)
+
+    def load_platform_plugins(self, platform_type=None):
+        platform_type = platform_type or self.get_option("platform_type")
+
+        if platform_type:
+            self._terminal = terminal_loader.get(platform_type, self)
             if not self._terminal:
                 raise AnsibleConnectionFailure(
-                    "network os %s is not supported" % self._network_os
+                    "network os %s is not supported" % platform_type
+                )
+            else:
+                self.queue_message(
+                    "vvvv",
+                    "loaded terminal plugin %s from path %s for network_os %s"
+                    % (
+                        self.terminal._load_name,
+                        self.terminal._original_path,
+                        platform_type,
+                    ),
                 )
 
-            self.cliconf = cliconf_loader.get(self._network_os, self)
+            self.cliconf = cliconf_loader.get(platform_type, self)
             if self.cliconf:
                 self._sub_plugin = {
                     "type": "cliconf",
@@ -381,21 +404,20 @@ def __init__(self, play_context, new_stdin, *args, **kwargs):
                     % (
                         self.cliconf._load_name,
                         self.cliconf._original_path,
-                        self._network_os,
+                        platform_type,
                     ),
                 )
             else:
                 self.queue_message(
                     "vvvv",
-                    "unable to load cliconf for network_os %s"
-                    % self._network_os,
+                    "unable to load cliconf for network_os %s" % platform_type,
                 )
         else:
             raise AnsibleConnectionFailure(
                 "Unable to automatically determine host network os. Please "
-                "manually configure ansible_network_os value for this host"
+                "manually configure platform_type value for this host"
             )
-        self.queue_message("log", "network_os is set to %s" % self._network_os)
+        self.queue_message("log", "platform_type is set to %s" % platform_type)
 
     @property
     def ssh_type_conn(self):
@@ -612,11 +634,6 @@ def _connect(self):
             if self._ssh_type == "paramiko":
                 self._ssh_shell.settimeout(command_timeout)
 
-            self.queue_message(
-                "vvvv",
-                "loaded terminal plugin for network_os %s" % self._network_os,
-            )
-
             terminal_initial_prompt = (
                 self.get_option("terminal_initial_prompt")
                 or self._terminal.terminal_initial_prompt