Require disk and container format on image-create

Currently glanceclient doesn't enforce disk-format or container-format
presence in the command line on image-create when providing image data
(with --file, --location, --copy-from), which means that the POST
request is made with the whole image and error is reported by Glance
API.

This post enforces presence of those arguments when image data is
provided so we can get the error quicker and avoid sending unnecessary
data over the network.

Change-Id: I5914fa9cfef190a028b374005adbf3a804b1b677
Closes-Bug: #1309272

glanceclient/common/utils.py

@@ -36,11 +36,15 @@ from oslo_utils import encodeutils
 from oslo_utils import strutils
 import prettytable
 
+from glanceclient import _i18n
 from glanceclient import exc
 
+_ = _i18n._
+
 _memoized_property_lock = threading.Lock()
 
 SENSITIVE_HEADERS = ('X-Auth-Token', )
+REQUIRED_FIELDS_ON_DATA = ('disk_format', 'container_format')
 
 
 # Decorator for cli-args
@@ -53,6 +57,47 @@ def arg(*args, **kwargs):
     return _decorator
 
 
+def on_data_require_fields(data_fields, required=REQUIRED_FIELDS_ON_DATA):
+    """Decorator to check commands' validity
+
+    This decorator checks that required fields are present when image
+    data has been supplied via command line arguments or via stdin
+
+    On error throws CommandError exception with meaningful message.
+
+    :param data_fields: Which fields' presence imply image data
+    :type data_fields: iter
+    :param required: Required fields
+    :type required: iter
+    :return: function decorator
+    """
+
+    def args_decorator(func):
+        def prepare_fields(fields):
+            args = ('--' + x.replace('_', '-') for x in fields)
+            return ', '.join(args)
+
+        def func_wrapper(gc, args):
+            # Set of arguments with data
+            fields = set(a[0] for a in vars(args).items() if a[1])
+
+            # Fields the conditional requirements depend on
+            present = fields.intersection(data_fields)
+
+            # How many conditional requirements are missing
+            missing = set(required) - fields
+
+            # We use get_data_file to check if data is provided in stdin
+            if (present or get_data_file(args)) and missing:
+                msg = (_("error: Must provide %(req)s when using %(opt)s.") %
+                       {'req': prepare_fields(missing),
+                        'opt': prepare_fields(present) or 'stdin'})
+                raise exc.CommandError(msg)
+            return func(gc, args)
+        return func_wrapper
+    return args_decorator
+
+
 def schema_args(schema_getter, omit=None):
     omit = omit or []
     typemap = {