ansible-doc: fix traceback when passing -a arg (#52036)

Fixes #52034

lib/ansible/cli/doc.py

@@ -80,7 +80,7 @@ class DocCLI(CLI):
 
         # process all plugins of type
         if options.all_plugins:
-            args = self.get_all_plugins_of_type(options['type'])
+            args = self.get_all_plugins_of_type(options.type)
             if options.module_path:
                 display.warning('Ignoring "--module-path/-M" option as "--all/-a" only displays builtins')
 
@@ -283,6 +283,10 @@ class DocCLI(CLI):
             display.vvvv("%s does not exist" % path)
             return plugin_list
 
+        if not os.path.isdir(path):
+            display.vvvv("%s is not a directory" % path)
+            return plugin_list
+
         bkey = ptype.upper()
         for plugin in os.listdir(path):
             display.vvvv("Found %s" % plugin)

test/units/cli/test_doc.py

@@ -0,0 +1,12 @@
+# Copyright: (c) 2019, Ansible Project
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+from ansible.cli.doc import DocCLI
+
+
+def test_parsing_all_option():
+    doc_cli = DocCLI(['/n/ansible-doc', '-a'])
+    doc_cli.parse()