Moved validate_required_arg() to common _options.py module

Details:

* The 'pywbemcli instance' command group has a --help-instancename option that
  shows a help message for instance names. The instance commands that have
  this option all define their positional arguments at the Click level with
  required=False, even when they are actually required. If they are required,
  the presence of the argument is validated using the validate_required_arg()
  function that is invoked after the --help-... option has been processed.
  This allows using the --help-... option without having to specify required
  positional arguments.

  This change moves the validate_required_arg() function from the
  pywbemcli/_cmd_instance.py module to the common _options.py module so it
  can be used also by the future pywbemlistener command.

Signed-off-by: Andreas Maier <[email protected]>

pywbemtools/_options.py

@@ -52,3 +52,19 @@ def _add_options(func):
         return func
 
     return _add_options
+
+
+def validate_required_arg(value, metavar):
+    """
+    Validate that a required CLI argument is present, and raise a usage error
+    otherwise.
+
+    This function is used for required arguments in cases where the command
+    has a --help-... option, so that the option can be used without specifying
+    the required arguments. Just using is_eager on the option is not sufficient
+    for that.
+    """
+    if not value:
+        raise click.UsageError(
+            "Missing argument '{}'.".format(metavar),
+            click.get_current_context())

pywbemtools/pywbemcli/_cmd_instance.py

@@ -46,7 +46,7 @@
 from ._cmd_class import get_namespaces, enumerate_classes_filtered
 from .._click_extensions import PywbemtoolsGroup, PywbemtoolsCommand, \
     CMD_OPTS_TXT, GENERAL_OPTS_TXT, SUBCMD_HELP_TXT
-from .._options import add_options, help_option
+from .._options import add_options, help_option, validate_required_arg
 from .._output_formatting import validate_output_format, format_table, \
     warning_msg
 
@@ -675,17 +675,6 @@ def instance_shrub(context, instancename, **options):
 ####################################################################
 
 
-def validate_required_arg(value, metavar):
-    """
-    Validate that a required CLI argument is present, and raise a usage error
-    otherwise.
-    """
-    if not value:
-        raise click.UsageError(
-            "Missing argument '{}'.".format(metavar),
-            click.get_current_context())
-
-
 def show_help_instancename():
     """
     Show the help message on how to specify an instance using INSTANCENAME