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/vars.py

@@ -0,0 +1,132 @@
+# -*- 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 VarMeta(object):
+    NOTHING = object()
+
+    def __init__(self, diff=False, output=True, change=None, fact=False):
+        self.init = False
+        self.initial_value = None
+        self.value = None
+
+        self.diff = diff
+        self.change = diff if change is None else change
+        self.output = output
+        self.fact = fact
+
+    def set(self, diff=None, output=None, change=None, fact=None, initial_value=NOTHING):
+        if diff is not None:
+            self.diff = diff
+        if output is not None:
+            self.output = output
+        if change is not None:
+            self.change = change
+        if fact is not None:
+            self.fact = fact
+        if initial_value is not self.NOTHING:
+            self.initial_value = initial_value
+
+    def set_value(self, value):
+        if not self.init:
+            self.initial_value = value
+            self.init = True
+        self.value = value
+        return self
+
+    @property
+    def has_changed(self):
+        return self.change and (self.initial_value != self.value)
+
+    @property
+    def diff_result(self):
+        return None if not (self.diff and self.has_changed) else {
+            'before': self.initial_value,
+            'after': self.value,
+        }
+
+    def __str__(self):
+        return "<VarMeta: value={0}, initial={1}, diff={2}, output={3}, change={4}>".format(
+            self.value, self.initial_value, self.diff, self.output, self.change
+        )
+
+
+class VarDict(object):
+    def __init__(self):
+        self._data = dict()
+        self._meta = dict()
+
+    def __getitem__(self, item):
+        return self._data[item]
+
+    def __setitem__(self, key, value):
+        self.set(key, value)
+
+    def __getattr__(self, item):
+        try:
+            return self._data[item]
+        except KeyError:
+            return getattr(self._data, item)
+
+    def __setattr__(self, key, value):
+        if key in ('_data', '_meta'):
+            super(VarDict, self).__setattr__(key, value)
+        else:
+            self.set(key, value)
+
+    def meta(self, name):
+        return self._meta[name]
+
+    def set_meta(self, name, **kwargs):
+        self.meta(name).set(**kwargs)
+
+    def set(self, name, value, **kwargs):
+        if name in ('_data', '_meta'):
+            raise ValueError("Names _data and _meta are reserved for use by ModuleHelper")
+        self._data[name] = value
+        if name in self._meta:
+            meta = self.meta(name)
+        else:
+            meta = VarMeta(**kwargs)
+        meta.set_value(value)
+        self._meta[name] = meta
+
+    def output(self):
+        return dict((k, v) for k, v in self._data.items() if self.meta(k).output)
+
+    def diff(self):
+        diff_results = [(k, self.meta(k).diff_result) for k in self._data]
+        diff_results = [dr for dr in diff_results if dr[1] is not None]
+        if diff_results:
+            before = dict((dr[0], dr[1]['before']) for dr in diff_results)
+            after = dict((dr[0], dr[1]['after']) for dr in diff_results)
+            return {'before': before, 'after': after}
+        return None
+
+    def facts(self):
+        facts_result = dict((k, v) for k, v in self._data.items() if self._meta[k].fact)
+        return facts_result if facts_result else None
+
+    def change_vars(self):
+        return [v for v in self._data if self.meta(v).change]
+
+    def has_changed(self, v):
+        return self._meta[v].has_changed
+
+
+class VarsMixin(object):
+
+    def __init__(self, module=None):
+        self.vars = VarDict()
+        super(VarsMixin, self).__init__(module)
+
+    def update_vars(self, meta=None, **kwargs):
+        if meta is None:
+            meta = {}
+        for k, v in kwargs.items():
+            self.vars.set(k, v, **meta)