Implement default omit filter

lib/ansible/runner/__init__.py

@@ -49,6 +49,7 @@ from ansible.module_common import ModuleReplacer
 from ansible.module_utils.splitter import split_args
 from ansible.cache import FactCache
 from ansible.utils import update_hash
+from ansible.utils import OMIT_PLACE_HOLDER
 
 module_replacer = ModuleReplacer(strip_comments=False)
 
@@ -740,14 +741,6 @@ class Runner(object):
         if self.su_user_var is not None:
             self.su_user = template.template(self.basedir, self.su_user_var, inject)
 
-        # allow module args to work as a dictionary
-        # though it is usually a string
-        new_args = ""
-        if type(module_args) == dict:
-            for (k,v) in module_args.iteritems():
-                new_args = new_args + "%s='%s' " % (k,v)
-            module_args = new_args
-
         # module_name may be dynamic (but cannot contain {{ ansible_ssh_user }})
         module_name  = template.template(self.basedir, module_name, inject)
 
@@ -872,6 +865,18 @@ class Runner(object):
         if self._early_needs_tmp_path(module_name, handler):
             tmp = self._make_tmp_path(conn)
 
+        # allow module args to work as a dictionary
+        # though it is usually a string
+        if type(module_args) == dict:
+            new_args = []
+            for (k, v) in module_args.iteritems():
+                # see if the value is OMIT_PLACE_HOLDER, if it is, skip it
+                arg_value = template.template(self.basedir, v, inject, fail_on_undefined=self.error_on_undefined_vars)
+                if arg_value.strip() == OMIT_PLACE_HOLDER:
+                    continue
+                new_args.append("%s='%s'" % (k, v))
+            module_args = ' '.join(new_args)
+
         # render module_args and complex_args templates
         try:
             # When templating module_args, we need to be careful to ensure

lib/ansible/runner/filter_plugins/core.py

@@ -15,6 +15,7 @@
 # You should have received a copy of the GNU General Public License
 # along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
 
+import os
 import base64
 import json
 import os.path
@@ -25,12 +26,14 @@ import glob
 import re
 import collections
 import operator as py_operator
+import hashlib
 from ansible import errors
-from ansible.utils import md5s
+from ansible.utils import md5s, OMIT_PLACE_HOLDER
 from distutils.version import LooseVersion, StrictVersion
 from random import SystemRandom
 from jinja2.filters import environmentfilter
 
+
 def to_nice_yaml(*a, **kw):
     '''Make verbose, human readable yaml'''
     return yaml.safe_dump(*a, indent=4, allow_unicode=True, default_flow_style=False, **kw)
@@ -234,6 +237,15 @@ def rand(environment, end, start=None, step=None):
     else:
         raise errors.AnsibleFilterError('random can only be used on sequences and integers')
 
+def default_omit(a):
+    try:
+        a
+    except NameError:
+        return OMIT_PLACE_HOLDER
+    else:
+        return a
+
+
 class FilterModule(object):
     ''' Ansible core jinja2 filters '''
 
@@ -305,5 +317,6 @@ class FilterModule(object):
 
             # random numbers
             'random': rand,
-        }
 
+            'default_omit': default_omit,
+        }

lib/ansible/utils/__init__.py

@@ -61,6 +61,7 @@ LOOKUP_REGEX = re.compile(r'lookup\s*\(')
 PRINT_CODE_REGEX = re.compile(r'(?:{[{%]|[%}]})')
 CODE_REGEX = re.compile(r'(?:{%|%})')
 
+
 try:
     import json
 except ImportError:
@@ -110,6 +111,11 @@ try:
 except ImportError:
     pass
 
+
+OMIT_PLACE_HOLDER = (
+    '__omit_place_holder__%s' % _md5(os.urandom(64)).hexdigest()
+)
+
 ###############################################################
 # Abstractions around keyczar
 ###############################################################