Add failed_when module variable.

Implementation note: Ternery operator trick for python prior to 2.5 is used.
(test and [when_true_value] or [when_false_value])[0]
http://stackoverflow.com/questions/394809/ternary-conditional-operator-in-python#comment1466794_394887

lib/ansible/callbacks.py

@@ -189,7 +189,7 @@ class AggregateStats(object):
 
         for (host, value) in runner_results.get('contacted', {}).iteritems():
             if not ignore_errors and (('failed' in value and bool(value['failed'])) or
-                ('rc' in value and value['rc'] != 0)):
+                ('failed_when_result' in value and [value['failed_when_result']] or ['rc' in value and value['rc'] != 0])[0]):
                 self._increment('failures', host)
             elif 'skipped' in value and bool(value['skipped']):
                 self._increment('skipped', host)

lib/ansible/playbook/task.py

@@ -29,7 +29,7 @@ class Task(object):
         'delegate_to', 'first_available_file', 'ignore_errors',
         'local_action', 'transport', 'sudo', 'sudo_user', 'sudo_pass',
         'items_lookup_plugin', 'items_lookup_terms', 'environment', 'args',
-        'any_errors_fatal', 'changed_when', 'always_run'
+        'any_errors_fatal', 'changed_when', 'failed_when', 'always_run'
     ]
 
     # to prevent typos and such
@@ -38,7 +38,7 @@ class Task(object):
          'first_available_file', 'include', 'tags', 'register', 'ignore_errors',
          'delegate_to', 'local_action', 'transport', 'sudo', 'sudo_user',
          'sudo_pass', 'when', 'connection', 'environment', 'args',
-         'any_errors_fatal', 'changed_when', 'always_run'
+         'any_errors_fatal', 'changed_when', 'failed_when', 'always_run'
     ]
 
     def __init__(self, play, ds, module_vars=None, default_vars=None, additional_conditions=None):
@@ -88,7 +88,7 @@ class Task(object):
                 else:
                     raise errors.AnsibleError("cannot find lookup plugin named %s for usage in with_%s" % (plugin_name, plugin_name))
 
-            elif x in [ 'changed_when', 'when']:
+            elif x in [ 'changed_when', 'failed_when', 'when']:
                 ds[x] = "jinja2_compare %s" % (ds[x])
             elif x.startswith("when_"):
                 if 'when' in ds:
@@ -167,6 +167,11 @@ class Task(object):
         if self.changed_when is not None:
             self.changed_when = utils.compile_when_to_only_if(self.changed_when)
 
+        self.failed_when = ds.get('failed_when', None)
+
+        if self.failed_when is not None:
+            self.failed_when = utils.compile_when_to_only_if(self.failed_when)
+
         self.async_seconds = int(ds.get('async', 0))  # not async by default
         self.async_poll_interval = int(ds.get('poll', 10))  # default poll = 10 seconds
         self.notify = ds.get('notify', [])
@@ -223,6 +228,7 @@ class Task(object):
         self.module_vars['ignore_errors'] = self.ignore_errors
         self.module_vars['register'] = self.register
         self.module_vars['changed_when'] = self.changed_when
+        self.module_vars['failed_when'] = self.failed_when
         self.module_vars['always_run'] = self.always_run
 
         # tags allow certain parts of a playbook to be run without running the whole playbook

lib/ansible/runner/__init__.py

@@ -507,7 +507,7 @@ class Runner(object):
                 for x in results:
                     if x.get('changed') == True:
                         all_changed = True
-                    if (x.get('failed') == True) or (('rc' in x) and (x['rc'] != 0)):
+                    if (x.get('failed') == True) or ('failed_when_result' in x and [x['failed_when_result']] or [('rc' in x) and (x['rc'] != 0)])[0]:
                         all_failed = True
                         break
             msg = 'All items completed'
@@ -669,13 +669,17 @@ class Runner(object):
             )
 
             changed_when = self.module_vars.get('changed_when')
-            if changed_when is not None:
+            failed_when = self.module_vars.get('failed_when')
+            if changed_when is not None or failed_when is not None:
                 register = self.module_vars.get('register')
                 if  register is not None:
                     if 'stdout' in data:
                         data['stdout_lines'] = data['stdout'].splitlines()
                     inject[register] = data
-                data['changed'] = utils.check_conditional(changed_when, self.basedir, inject, fail_on_undefined=self.error_on_undefined_vars)
+                if changed_when is not None:
+                    data['changed'] = utils.check_conditional(changed_when, self.basedir, inject, fail_on_undefined=self.error_on_undefined_vars)
+                if failed_when is not None:
+                    data['failed_when_result'] = data['failed'] = utils.check_conditional(failed_when, self.basedir, inject, fail_on_undefined=self.error_on_undefined_vars)
 
             if is_chained:
                 # no callbacks

lib/ansible/runner/return_data.py

@@ -59,5 +59,5 @@ class ReturnData(object):
         return self.comm_ok
 
     def is_successful(self):
-        return self.comm_ok and (self.result.get('failed', False) == False) and (self.result.get('rc',0) == 0)
+        return self.comm_ok and (self.result.get('failed', False) == False) and ('failed_when_result' in self.result and [not self.result['failed_when_result']] or [self.result.get('rc',0) == 0])[0]
 

test/TestPlayBook.py

@@ -474,6 +474,34 @@ class TestPlaybook(unittest.TestCase):
 
        assert utils.jsonify(expected, format=True) == utils.jsonify(actual,format=True)
 
+   def test_playbook_failed_when(self):
+       test_callbacks = TestCallbacks()
+       playbook = ansible.playbook.PlayBook(
+           playbook=os.path.join(self.test_dir, 'playbook-failed_when.yml'),
+           host_list='test/ansible_hosts',
+           stats=ans_callbacks.AggregateStats(),
+           callbacks=test_callbacks,
+           runner_callbacks=test_callbacks
+       )
+       actual = playbook.run()
+
+       # if different, this will output to screen
+       print "**ACTUAL**"
+       print utils.jsonify(actual, format=True)
+       expected =  {
+           "localhost": {
+               "changed": 2,
+               "failures": 1,
+               "ok": 2,
+               "skipped": 0,
+               "unreachable": 0
+           }
+       }
+       print "**EXPECTED**"
+       print utils.jsonify(expected, format=True)
+
+       assert utils.jsonify(expected, format=True) == utils.jsonify(actual,format=True)
+
 
    def test_playbook_always_run(self):
       test_callbacks = TestCallbacks()

test/playbook-failed_when.yml

+---
+- hosts: all
+  connection: local
+  gather_facts: False
+
+  tasks:
+  - action: shell exit 0
+    register: exit
+    failed_when: not exit.rc in [0, 1]
+  - action: shell exit 1
+    register: exit
+    failed_when: exit.rc not in [0, 1]
+  - action: shell exit 2
+    register: exit
+    failed_when: exit.rc not in [0, 1]