Add module common code to allow it to be easier to indicate whether arguments are mutually exclusive, required in conjunction, or whether one of a list of arguments is required. This simplifies writing Python modules.

lib/ansible/module_common.py

@@ -55,11 +55,14 @@ except ImportError:
 
 class AnsibleModule(object):
 
-    def __init__(self, argument_spec, bypass_checks=False, no_log=False, check_invalid_arguments=True):
+    def __init__(self, argument_spec, bypass_checks=False, no_log=False, 
+        check_invalid_arguments=True, mutually_exclusive=None, required_together=None,
+        required_one_of=None):
+
         '''
         common code for quickly building an ansible module in Python
         (although you can write modules in anything that can return JSON)
-        see library/slurp and others for examples
+        see library/* for examples
         '''
 
         self.argument_spec = argument_spec
@@ -77,12 +80,14 @@ class AnsibleModule(object):
         if not bypass_checks:
             self._check_required_arguments()
             self._check_argument_types()
+            self._check_mutually_exclusive(mutually_exclusive)
+            self._check_required_together(required_together)
+            self._check_required_one_of(required_one_of)
 
         self._set_defaults(pre=False)
         if not no_log:
             self._log_invocation()
 
-
     def _handle_aliases(self):
         for (k,v) in self.argument_spec.iteritems():
             self._legal_inputs.append(k)
@@ -106,6 +111,39 @@ class AnsibleModule(object):
             if k not in self._legal_inputs:
                 self.fail_json(msg="unsupported parameter for module: %s" % k)
 
+    def _count_terms(self, check):
+        count = 0
+        for term in check:
+           if term in self.params:
+               count += 1
+        return count
+
+    def _check_mutually_exclusive(self, spec):
+        if spec is None:
+            return
+        for check in spec:
+            count = self._count_terms(check)
+            if count > 1:
+                self.fail_json(msg="parameters are mutually exclusive: %s" % check)
+
+    def _check_required_one_of(self, spec):
+        if spec is None:
+            return
+        for check in spec:
+            count = self._count_terms(check)
+            if count == 0:
+                self.fail_json(msg="one of the following is required: %s" % check)
+
+    def _check_required_together(self, spec):
+        if spec is None:
+            return
+        for check in spec:
+            counts = [ self.count_terms([field]) for field in check ]
+            non_zero = [ c for c in counts if c > 0 ]
+            if len(non_zero) > 0:
+                if 0 in counts:
+                    self.fail_json(msg="parameters are required together: %s" % check) 
+
     def _check_required_arguments(self):
         ''' ensure all required arguments are present '''
         missing = []