Adds 'ansible_check_mode' boolean magic variable

* Makes it possible to pass any options variable to VariableManager
  by changing `load_options_vars(options)` in `lib/ansible/utils/vars.py`

docsite/rst/playbooks_checkmode.rst

@@ -38,7 +38,25 @@ Example::
 
 As a reminder, a task with a `when` clause evaluated to false, will
 still be skipped even if it has a `always_run` clause evaluated to
-true.
+true. 
+
+Also if you want to skip, or ignore errors on some tasks in check mode
+you can use a boolean magic variable `ansible_check_mode` (added in version 2.1)
+which will be set to `True` during check mode.
+
+Example::
+
+    tasks:
+
+      - name: this task will be skipped in check mode
+        git: repo=ssh://git@github.com/mylogin/hello.git dest=/home/mylogin/hello
+        when: not ansible_check_mode
+
+      - name: this task will ignore errors in check mode
+        git: repo=ssh://git@github.com/mylogin/hello.git dest=/home/mylogin/hello
+        ignore_errors: "{{ ansible_check_mode }}"
+
+
 
 .. _diff_mode:
 

docsite/rst/playbooks_variables.rst

@@ -674,7 +674,9 @@ Don't worry about any of this unless you think you need it.  You'll know when yo
 
 Also available, ``inventory_dir`` is the pathname of the directory holding Ansible's inventory host file, ``inventory_file`` is the pathname and the filename pointing to the Ansible's inventory host file.
 
-And finally, ``role_path`` will return the current role's pathname (since 1.8). This will only work inside a role.
+We then have ``role_path`` which will return the current role's pathname (since 1.8). This will only work inside a role.
+
+And finally, ``ansible_check_mode`` (added in version 2.1), a boolean magic variable which will be set to ``True`` if you run Ansible with ``--check``.
 
 .. _variable_file_separation_details:
 

lib/ansible/cli/adhoc.py

@@ -32,6 +32,7 @@ from ansible.parsing.splitter import parse_kv
 from ansible.playbook.play import Play
 from ansible.plugins import get_all_plugin_loaders
 from ansible.utils.vars import load_extra_vars
+from ansible.utils.vars import load_options_vars
 from ansible.utils.unicode import to_unicode
 from ansible.vars import VariableManager
 
@@ -123,6 +124,8 @@ class AdHocCLI(CLI):
         variable_manager = VariableManager()
         variable_manager.extra_vars = load_extra_vars(loader=loader, options=self.options)
 
+        variable_manager.options_vars = load_options_vars(self.options)
+
         inventory = Inventory(loader=loader, variable_manager=variable_manager, host_list=self.options.inventory)
         variable_manager.set_inventory(inventory)
 

lib/ansible/cli/playbook.py

@@ -33,6 +33,7 @@ from ansible.parsing.dataloader import DataLoader
 from ansible.playbook.block import Block
 from ansible.playbook.play_context import PlayContext
 from ansible.utils.vars import load_extra_vars
+from ansible.utils.vars import load_options_vars
 from ansible.vars import VariableManager
 
 try:
@@ -125,6 +126,8 @@ class PlaybookCLI(CLI):
         variable_manager = VariableManager()
         variable_manager.extra_vars = load_extra_vars(loader=loader, options=self.options)
 
+        variable_manager.options_vars = load_options_vars(self.options)
+
         # create the inventory, and filter it based on the subset specified (if any)
         inventory = Inventory(loader=loader, variable_manager=variable_manager, host_list=self.options.inventory)
         variable_manager.set_inventory(inventory)

lib/ansible/utils/vars.py

@@ -111,6 +111,13 @@ def load_extra_vars(loader, options):
         extra_vars = combine_vars(extra_vars, data)
     return extra_vars
 
+def load_options_vars(options):
+    options_vars = {}
+    # For now only return check mode, but we can easily return more
+    # options if we need variables for them
+    options_vars['ansible_check_mode'] = options.check
+    return options_vars
+
 def isidentifier(ident):
     """
     Determines, if string is valid Python identifier using the ast module.

lib/ansible/vars/__init__.py

@@ -99,6 +99,7 @@ class VariableManager:
         self._inventory = None
         self._hostvars = None
         self._omit_token = '__omit_place_holder__%s' % sha1(os.urandom(64)).hexdigest()
+        self._options_vars = defaultdict(dict)
 
     def __getstate__(self):
         data = dict(
@@ -109,6 +110,7 @@ class VariableManager:
             host_vars_files = self._host_vars_files,
             group_vars_files = self._group_vars_files,
             omit_token = self._omit_token,
+            options_vars = self._options_vars,
             #inventory = self._inventory,
         )
         return data
@@ -122,6 +124,7 @@ class VariableManager:
         self._group_vars_files = data.get('group_vars_files', defaultdict(dict))
         self._omit_token = data.get('omit_token', '__omit_place_holder__%s' % sha1(os.urandom(64)).hexdigest())
         self._inventory = data.get('inventory', None)
+        self._options_vars = data.get('options_vars', dict())
 
     def _get_cache_entry(self, play=None, host=None, task=None):
         play_id = "NONE"
@@ -152,6 +155,17 @@ class VariableManager:
     def set_inventory(self, inventory):
         self._inventory = inventory
 
+    @property
+    def options_vars(self):
+        ''' ensures a clean copy of the options_vars are made '''
+        return self._options_vars.copy()
+
+    @options_vars.setter
+    def options_vars(self, value):
+        ''' ensures a clean copy of the options_vars are used to set the value '''
+        assert isinstance(value, dict)
+        self._options_vars = value.copy()
+
     def _preprocess_vars(self, a):
         '''
         Ensures that vars contained in the parameter passed in are
@@ -392,6 +406,9 @@ class VariableManager:
         # the 'omit' value alows params to be left out if the variable they are based on is undefined
         variables['omit'] = self._omit_token
         variables['ansible_version'] = CLI.version_info(gitinfo=False)
+        # Set options vars
+        for option, option_value in self._options_vars.iteritems():
+            variables[option] = option_value
 
         if self._hostvars is not None and include_hostvars:
             variables['hostvars'] = self._hostvars

test/units/vars/test_variable_manager.py

@@ -49,6 +49,8 @@ class TestVariableManager(unittest.TestCase):
             del vars['vars']
         if 'ansible_version' in vars:
             del vars['ansible_version']
+        if 'ansible_check_mode' in vars:
+            del vars['ansible_check_mode']
 
         self.assertEqual(vars, dict(playbook_dir='.'))