ModuleHelper variables management (#2162) (#2178)

* added metadata for variables in module helper

* adjustments

* added separate support for tracking changes

* rewrote the diff code

* added integration test for module_helper

* using ansible.module_utils.common.dict_transformations.dict_merge

* improved dependency management

* restore ModuleHelper to base classes of CmdStateModuleHelper

* added assertions to ensure the failing module name appears in the error messages

* added test code for state-based modules

* fixed test name

* renamed class to VarMeta

* small fixes

* fixes from the PR

* fixed VarDict.__set_attr__

* added VarDict.__getitem__()

* added changelog fragment

* adjustments per PR

* ModuleHelper.output is now aware of conflicting variable names

* Update plugins/module_utils/module_helper.py

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

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit d2070277e8)

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

tests/unit/plugins/module_utils/test_module_helper.py

@@ -9,7 +9,7 @@ __metaclass__ = type
 import pytest
 
 from ansible_collections.community.general.plugins.module_utils.module_helper import (
-    ArgFormat, DependencyCtxMgr, ModuleHelper
+    ArgFormat, DependencyCtxMgr, ModuleHelper, VarMeta
 )
 
 
@@ -105,3 +105,58 @@ def test_dependency_ctxmgr():
     with ctx:
         import sys
     assert ctx.has_it
+
+
+def test_variable_meta():
+    meta = VarMeta()
+    assert meta.output is False
+    assert meta.diff is False
+    assert meta.value is None
+    meta.set_value("abc")
+    assert meta.initial_value == "abc"
+    assert meta.value == "abc"
+    assert meta.diff_result is None
+    meta.set_value("def")
+    assert meta.initial_value == "abc"
+    assert meta.value == "def"
+    assert meta.diff_result is None
+
+
+def test_variable_meta_diff():
+    meta = VarMeta(diff=True)
+    assert meta.output is False
+    assert meta.diff is True
+    assert meta.value is None
+    meta.set_value("abc")
+    assert meta.initial_value == "abc"
+    assert meta.value == "abc"
+    assert meta.diff_result is None
+    meta.set_value("def")
+    assert meta.initial_value == "abc"
+    assert meta.value == "def"
+    assert meta.diff_result == {"before": "abc", "after": "def"}
+    meta.set_value("ghi")
+    assert meta.initial_value == "abc"
+    assert meta.value == "ghi"
+    assert meta.diff_result == {"before": "abc", "after": "ghi"}
+
+
+def test_vardict():
+    vd = ModuleHelper.VarDict()
+    vd.set('a', 123)
+    assert vd['a'] == 123
+    assert vd.a == 123
+    assert 'a' in vd._meta
+    assert vd.meta('a').output is True
+    assert vd.meta('a').diff is False
+    assert vd.meta('a').change is False
+    vd['b'] = 456
+    vd.set_meta('a', diff=True, change=True)
+    vd.set_meta('b', diff=True, output=False)
+    vd['c'] = 789
+    vd['a'] = 'new_a'
+    vd['c'] = 'new_c'
+    assert vd.a == 'new_a'
+    assert vd.c == 'new_c'
+    assert vd.output() == {'a': 'new_a', 'c': 'new_c'}
+    assert vd.diff() == {'before': {'a': 123}, 'after': {'a': 'new_a'}}, "diff={0}".format(vd.diff())