module_helper.py Breakdown (#2393)

* break down of module_helper into smaller pieces, keeping compatibility

* removed abc.ABC (py3 only) from code + fixed reference to vars.py

* multiple changes:

- mh.base - moved more functionalities to ModuleHelperBase
- mh.mixins.(cmd, state) - CmdMixin no longer inherits from ModuleHelperBase
- mh.mixins.deps - DependencyMixin now overrides run() method to test dependency
- mh.mixins.vars - created class VarsMixin
- mh.module_helper - moved functions to base class, added VarsMixin
- module_helper - importing AnsibleModule as well, for backward compatibility in test

* removed unnecessary __all__

* make pylint happy

* PR adjustments + bot config + changelog frag

* Update plugins/module_utils/mh/module_helper.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update plugins/module_utils/mh/module_helper.py

Co-authored-by: Felix Fontein <felix@fontein.de>

Co-authored-by: Felix Fontein <felix@fontein.de>

plugins/module_utils/mh/mixins/state.py

@@ -0,0 +1,39 @@
+# -*- coding: utf-8 -*-
+# (c) 2020, Alexei Znamensky <russoz@gmail.com>
+# Copyright: (c) 2020, Ansible Project
+# Simplified BSD License (see licenses/simplified_bsd.txt or https://opensource.org/licenses/BSD-2-Clause)
+
+from __future__ import absolute_import, division, print_function
+__metaclass__ = type
+
+
+class StateMixin(object):
+    state_param = 'state'
+    default_state = None
+
+    def _state(self):
+        state = self.module.params.get(self.state_param)
+        return self.default_state if state is None else state
+
+    def _method(self, state):
+        return "{0}_{1}".format(self.state_param, state)
+
+    def __run__(self):
+        state = self._state()
+        self.vars.state = state
+
+        # resolve aliases
+        if state not in self.module.params:
+            aliased = [name for name, param in self.module.argument_spec.items() if state in param.get('aliases', [])]
+            if aliased:
+                state = aliased[0]
+                self.vars.effective_state = state
+
+        method = self._method(state)
+        if not hasattr(self, method):
+            return self.__state_fallback__()
+        func = getattr(self, method)
+        return func()
+
+    def __state_fallback__(self):
+        raise ValueError("Cannot find method: {0}".format(self._method(self._state())))