Fall-back to show configuration on old IOSXR devices (#22900)

In old IOSXR versions, 'show commit changes diff' does not work.
Fall-back to 'show configuration' if that command fails so execution
can move forward.

Fixes #22235

lib/ansible/module_utils/iosxr.py

@@ -85,7 +85,7 @@ def run_commands(module, commands, check_rc=True):
         responses.append(out)
     return responses
 
-def load_config(module, commands, commit=False, replace=False, comment=None):
+def load_config(module, commands, warnings, commit=False, replace=False, comment=None):
 
     rc, out, err = exec_command(module, 'configure terminal')
     if rc != 0:
@@ -106,6 +106,13 @@ def load_config(module, commands, commit=False, replace=False, comment=None):
         module.fail_json(msg=err, commands=commands, rc=rc)
 
     rc, diff, err = exec_command(module, 'show commit changes diff')
+    if rc != 0:
+        # If we failed, maybe we are in an old version so
+        # we run show configuration instead
+        rc, diff, err = exec_command(module, 'show configuration')
+        if module._diff:
+            warnings.append('device platform does not support config diff')
+
     if commit:
         cmd = 'commit'
         if comment:

lib/ansible/modules/network/iosxr/_iosxr_template.py

@@ -146,7 +146,7 @@ def main():
         commands = [c.strip() for c in str(candidate).split('\n')]
 
     if commands:
-        load_config(module, commands, not module.check_mode)
+        load_config(module, commands, result['warnings'], not module.check_mode)
         result['changed'] = not module.check_mode
 
     result['updates'] = commands

lib/ansible/modules/network/iosxr/iosxr_config.py

@@ -240,8 +240,8 @@ def run(module, result):
 
             result['commands'] = commands
 
-        diff = load_config(module, commands, not check_mode,
+        diff = load_config(module, commands, result['warnings'],
-                           replace_config, comment)
+                           not check_mode, replace_config, comment)
         if diff:
             result['diff'] = dict(prepared=diff)
             result['changed'] = True

lib/ansible/modules/network/iosxr/iosxr_system.py

@@ -243,7 +243,7 @@ def main():
 
     if commands:
         if not module.check_mode:
-            load_config(module, commands, commit=True)
+            load_config(module, commands, result['warnings'], commit=True)
         result['changed'] = True
 
     module.exit_json(**result)