Fix required argument validation

cleo/application.py

@@ -528,7 +528,7 @@ def get_command_name(self, input_):
 
     def get_default_input_definition(self):
         return InputDefinition([
-            InputArgument('command', InputArgument.REQUIRED, 'The command to execute'),
+            InputArgument('command', InputArgument.REQUIRED, 'The command to execute', is_application_argument=True),
 
             InputOption('--help', '-h', InputOption.VALUE_NONE, 'Display this help message'),
             InputOption('--quiet', '-q', InputOption.VALUE_NONE, 'Do not output any message'),

cleo/inputs/input.py

@@ -64,8 +64,17 @@ def parse(self):
         raise NotImplementedError()
 
     def validate(self):
-        if len(self.get_arguments()) < self.definition.get_argument_required_count():
-            raise MissingArguments('Not enough arguments')
+        current_args = self.get_arguments()
+
+        required_arguments = [
+            argument
+            for argument in self.definition.get_arguments()
+            if argument.is_required() and not argument.is_application_argument()
+        ]
+
+        for argument in required_arguments:
+            if current_args.get(argument.get_name()) is None:
+                raise MissingArguments('Not enough arguments')
 
         self.validate_arguments()
         self.validate_options()

cleo/inputs/input_argument.py

@@ -34,7 +34,7 @@ class InputArgument(object):
     IS_LIST = 4
 
     def __init__(self, name, mode=None,
-                 description='', default=None, validator=None):
+                 description='', default=None, validator=None, is_application_argument=False):
         """
         Constructor
 
@@ -58,6 +58,7 @@ def __init__(self, name, mode=None,
         self._mode = mode
         self._description = description or ''
         self._validator = VALIDATORS.get(validator)
+        self._is_application_argument = is_application_argument
 
         self.set_default(default)
 
@@ -88,6 +89,15 @@ def is_list(self):
         """
         return self.__class__.IS_LIST == (self.__class__.IS_LIST & self._mode)
 
+    def is_application_argument(self):
+        """
+        Returns True if the argument is from application
+
+        :return: True if argument is from application, False otherwise
+        :rtype: bool
+        """
+        return self._is_application_argument
+
     def set_default(self, default=None):
         """
         Sets the default value.