Optionally fail task on undefined variables

This patch introduces a new configuration option called
error_on_undefined_vars, which defaults to false.

If this option is set to true, then a task which has unevaluated
variables in its arguments will fail instead of running. Output looks
like this:

    TASK: [set rabbitmq password] *************************************************
    fatal: [10.20.0.7] => Undefined variables: rabbitmq_user, rabbitmq_password

lib/ansible/constants.py

@@ -110,6 +110,8 @@ ANSIBLE_NOCOWS                 = get_config(p, DEFAULTS, 'nocows', 'ANSIBLE_NOCO
 ANSIBLE_SSH_ARGS               = get_config(p, 'ssh_connection', 'ssh_args', 'ANSIBLE_SSH_ARGS', None)
 ZEROMQ_PORT                    = int(get_config(p, 'fireball', 'zeromq_port', 'ANSIBLE_ZEROMQ_PORT', 5099))
 
+DEFAULT_UNDEFINED_VAR_BEHAVIOR = get_config(p, DEFAULTS, 'error_on_undefined_vars', 'ANSIBLE_ERROR_ON_UNDEFINED_VARS', False)
+
 # non-configurable things
 DEFAULT_SUDO_PASS         = None
 DEFAULT_REMOTE_PASS       = None

lib/ansible/errors.py

@@ -32,3 +32,6 @@ class AnsibleConnectionFailed(AnsibleError):
 
 class AnsibleYAMLValidationFailed(AnsibleError):
     pass
+
+class AnsibleUndefinedVariable(AnsibleError):
+    pass

lib/ansible/runner/__init__.py

@@ -30,6 +30,7 @@ import base64
 import sys
 import shlex
 import pipes
+import re
 
 import ansible.constants as C
 import ansible.inventory
@@ -128,7 +129,8 @@ class Runner(object):
         check=False,                        # don't make any changes, just try to probe for potential changes
         diff=False,                         # whether to show diffs for template files that change
         environment=None,                   # environment variables (as dict) to use inside the command
-        complex_args=None                   # structured data in addition to module_args, must be a dict
+        complex_args=None,                  # structured data in addition to module_args, must be a dict
+        error_on_undefined_vars=C.DEFAULT_UNDEFINED_VAR_BEHAVIOR # ex. False
         ):
 
         if not complex_args:
@@ -163,6 +165,7 @@ class Runner(object):
         self.is_playbook      = is_playbook
         self.environment      = environment
         self.complex_args     = complex_args
+        self.error_on_undefined_vars = error_on_undefined_vars
 
         self.callbacks.runner = self
 
@@ -435,11 +438,11 @@ class Runner(object):
                         raise errors.AnsibleError("args must be a dictionary, received %s" % complex_args)
 
                 result = self._executor_internal_inner(
-                     host, 
-                     self.module_name, 
-                     self.module_args, 
-                     inject, 
-                     port, 
+                     host,
+                     self.module_name,
+                     self.module_args,
+                     inject,
+                     port,
                      complex_args=complex_args
                 )
                 results.append(result.result)
@@ -626,7 +629,7 @@ class Runner(object):
         path = pipes.quote(path)
         # The following test needs to be SH-compliant.  BASH-isms will
         # not work if /bin/sh points to a non-BASH shell.
-        test = "rc=0; [ -r \"%s\" ] || rc=2; [ -f \"%s\" ] || rc=1; [ -d \"%s\" ] && rc=3" % ((path,) * 3) 
+        test = "rc=0; [ -r \"%s\" ] || rc=2; [ -f \"%s\" ] || rc=1; [ -d \"%s\" ] && rc=3" % ((path,) * 3)
         md5s = [
             "(/usr/bin/md5sum %s 2>/dev/null)" % path,  # Linux
             "(/sbin/md5sum -q %s 2>/dev/null)" % path,  # ?
@@ -673,8 +676,16 @@ class Runner(object):
 
     # *****************************************************
 
+    def _contains_undefined_vars(self, module_args):
+        ''' return true if there are undefined variables '''
+        return '{{' in module_args
+
     def _copy_module(self, conn, tmp, module_name, module_args, inject, complex_args=None):
         ''' transfer a module over SFTP, does not run it '''
+        if self.error_on_undefined_vars and self._contains_undefined_vars(module_args):
+            vars = re.findall(r'{{(.*?)}}', module_args)
+            raise errors.AnsibleUndefinedVariable("Undefined variables: %s" %
+                ', '.join(vars))
 
         # FIXME if complex args is none, set to {}