Fixing item loop when undefined variable errors occur because of missing attributes

Fixes a case where the variable 'foo' may exist, but the with_items loop
was used on something like 'foo.results', where 'results' was not a valid
attribute of 'foo'. Prior to this patch, conditionals were not evaluated
until later, meaning there was no opportunity to allow a test to skip the
task or item based on it being undefined.

lib/ansible/runner/__init__.py

@@ -663,9 +663,24 @@ class Runner(object):
                 if os.path.exists(filesdir):
                     basedir = filesdir
 
-            items_terms = self.module_vars.get('items_lookup_terms', '')
-            items_terms = template.template(basedir, items_terms, inject)
-            items = utils.plugins.lookup_loader.get(items_plugin, runner=self, basedir=basedir).run(items_terms, inject=inject)
+            try:
+                items_terms = self.module_vars.get('items_lookup_terms', '')
+                items_terms = template.template(basedir, items_terms, inject)
+                items = utils.plugins.lookup_loader.get(items_plugin, runner=self, basedir=basedir).run(items_terms, inject=inject)
+            except errors.AnsibleUndefinedVariable, e:
+                if 'has no attribute' in str(e):
+                    # the undefined variable was an attribute of a variable that does
+                    # exist, so try and run this through the conditional check to see
+                    # if the user wanted to skip something on being undefined
+                    if utils.check_conditional(self.conditional, self.basedir, inject, fail_on_undefined=True):
+                        # the conditional check passed, so we have to fail here
+                        raise
+                    else:
+                        # the conditional failed, so we skip this task
+                        result = utils.jsonify(dict(changed=False, skipped=True))
+                        self.callbacks.on_skipped(host, None)
+                        return ReturnData(host=host, result=result)
+
             # strip out any jinja2 template syntax within
             # the data returned by the lookup plugin
             items = utils._clean_data_struct(items, from_remote=True)

test/integration/roles/test_conditionals/tasks/main.yml

@@ -267,3 +267,28 @@
     that:
     - "result.changed"
 
+- name: test a with_items loop using a variable with a missing attribute
+  debug: var=item
+  with_items: foo.results
+  when: foo is defined and 'results' in foo
+  register: result
+
+- name: assert the task was skipped
+  assert:
+    that:
+    - "'skipped' in result"
+    - result.skipped
+
+- name: test a with_items loop skipping a single item
+  debug: var=item
+  with_items: items.results
+  when: item != 'b'
+  register: result
+
+- debug: var=result
+
+- name: assert only a single item was skipped
+  assert:
+    that:
+    - result.results|length == 3
+    - result.results[1].skipped

test/integration/roles/test_conditionals/vars/main.yml

+---
+# foo is a dictionary that will be used to check that
+# a conditional passes a with_items loop on a variable
+# with a missing attribute (ie. foo.results)
+foo:
+  bar: a
+
+items:
+  results:
+  - a
+  - b
+  - c
+