EOS add force_cfg_session_invalid argument (#1927)

Co-authored-by: Kevin Petremann <k.petremann@criteo.com>

docs/support/index.rst

@@ -141,6 +141,7 @@ ____________________________________
 * :code:`eos_fn0039_config` (eos) - Transform old style configuration to the new style, available beginning with EOS release 4.23.0, as per FN 0039. Beware
   that enabling this option will change the configuration you're loading through NAPALM. Default: ``False`` (won't change your configuration commands).
   .. versionadded:: 3.0.1
+* :code:`force_cfg_session_invalid` (eos) - Force the config_session to be cleared in case of issues, like `discard_config` failure. (default: ``False``)
 
 The transport argument
 ______________________

napalm/eos/eos.py

@@ -96,6 +96,8 @@ def __init__(self, hostname, username, password, timeout=60, optional_args=None)
         Optional args:
             * lock_disable (True/False): force configuration lock to be disabled (for external lock
                 management).
+            * force_cfg_session_invalid (True/False): force invalidation of the config session
+                in case of failure.
             * enable_password (True/False): Enable password for privilege elevation
             * eos_autoComplete (True/False): Allow for shortening of cli commands
             * transport (string): transport, eos_transport is a fallback for compatibility.
@@ -134,6 +136,10 @@ def __init__(self, hostname, username, password, timeout=60, optional_args=None)
         # Define locking method
         self.lock_disable = self.optional_args.pop("lock_disable", False)
 
+        self.force_cfg_session_invalid = self.optional_args.pop(
+            "force_cfg_session_invalid", False
+        )
+
         # eos_transport is there for backwards compatibility, transport is the preferred method
         transport = self.optional_args.get(
             "transport", self.optional_args.get("eos_transport", "https")
@@ -150,7 +156,6 @@ def _process_optional_args_ssh(self, optional_args):
         self.netmiko_optional_args = netmiko_args(optional_args)
 
     def _process_optional_args_eapi(self, optional_args):
-
         # Parse pyeapi transport class
         self.transport_class = self._parse_transport(self.transport)
 
@@ -543,8 +548,15 @@ def confirm_commit(self):
     def discard_config(self):
         """Implementation of NAPALM method discard_config."""
         if self.config_session is not None:
-            commands = [f"configure session {self.config_session} abort"]
-            self._run_commands(commands, encoding="text")
+            try:
+                commands = [f"configure session {self.config_session} abort"]
+                self._run_commands(commands, encoding="text")
+            except Exception:
+                # If discard fails, you might want to invalidate the config_session (esp. Salt)
+                # The config_session in EOS is used as the config lock.
+                if self.force_cfg_session_invalid:
+                    self.config_session = None
+                raise
             self.config_session = None
 
     def rollback(self):