[cloud] Improve Camel to Snake conversion in EC2 module_utils (#25015)

* Make camel_to_snake work on capitalized plurals

`TargetGroupARNs` should become `target_group_arns`, not
`target_group_ar_ns`

Promote `camel_to_snake` to top layer function but prefix
it with an underscore.

Add tests for improved `_camel_to_snake` function.

Reduce use of `re.compile` as it makes no sense when the
compilation result is not reused.

* Remove unused LooseVersion check

* Fix PLURALs case for camel_to_snake

Also renamed EXPECTED_CAMELIZATION to EXPECTED_SNAKIFICATION

lib/ansible/module_utils/ec2.py

@@ -47,12 +47,6 @@ try:
 except:
     HAS_BOTO3 = False
 
-try:
-    from distutils.version import LooseVersion
-    HAS_LOOSE_VERSION = True
-except:
-    HAS_LOOSE_VERSION = False
-
 from ansible.module_utils.six import string_types, binary_type, text_type
 
 
@@ -345,17 +339,27 @@ def paging(pause=0, marker_property='marker'):
     return wrapper
 
 
-def camel_dict_to_snake_dict(camel_dict):
+def _camel_to_snake(name):
 
-    def camel_to_snake(name):
+    def prepend_underscore_and_lower(m):
+        return '_' + m.group(0).lower()
 
     import re
+    # Cope with pluralized abbreviations such as TargetGroupARNs
+    # that would otherwise be rendered target_group_ar_ns
+    plural_pattern = r'[A-Z]{3,}s$'
+    s1 = re.sub(plural_pattern, prepend_underscore_and_lower, name)
+    # Handle when there was nothing before the plural_pattern
+    if s1.startswith("_") and not name.startswith("_"):
+        s1 = s1[1:]
+    # Remainder of solution seems to be https://stackoverflow.com/a/1176023
+    first_cap_pattern = r'(.)([A-Z][a-z]+)'
+    all_cap_pattern = r'([a-z0-9])([A-Z]+)'
+    s2 = re.sub(first_cap_pattern, r'\1_\2', s1)
+    return re.sub(all_cap_pattern, r'\1_\2', s2).lower()
 
-        first_cap_re = re.compile('(.)([A-Z][a-z]+)')
-        all_cap_re = re.compile('([a-z0-9])([A-Z])')
-        s1 = first_cap_re.sub(r'\1_\2', name)
 
-        return all_cap_re.sub(r'\1_\2', s1).lower()
+def camel_dict_to_snake_dict(camel_dict):
 
     def value_is_list(camel_list):
 
@@ -373,11 +377,11 @@ def camel_dict_to_snake_dict(camel_dict):
     snake_dict = {}
     for k, v in camel_dict.items():
         if isinstance(v, dict):
-            snake_dict[camel_to_snake(k)] = camel_dict_to_snake_dict(v)
+            snake_dict[_camel_to_snake(k)] = camel_dict_to_snake_dict(v)
         elif isinstance(v, list):
-            snake_dict[camel_to_snake(k)] = value_is_list(v)
+            snake_dict[_camel_to_snake(k)] = value_is_list(v)
         else:
-            snake_dict[camel_to_snake(k)] = v
+            snake_dict[_camel_to_snake(k)] = v
 
     return snake_dict
 

test/units/module_utils/ec2/test_camel_to_snake.py

@@ -0,0 +1,37 @@
+# -*- coding: utf-8 -*-
+# (c) 2017, Will Thames <will.thames@xvt.com.au>
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+from ansible.compat.tests import unittest
+from ansible.module_utils.ec2 import _camel_to_snake
+
+EXPECTED_SNAKIFICATION = {
+    'alllower': 'alllower',
+    'TwoWords': 'two_words',
+    'AllUpperAtEND': 'all_upper_at_end',
+    'AllUpperButPLURALs': 'all_upper_but_plurals',
+    'TargetGroupARNs': 'target_group_arns',
+    'HTTPEndpoints': 'http_endpoints',
+    'PLURALs': 'plurals'
+}
+
+
+class CamelToSnakeTestCase(unittest.TestCase):
+
+    def test_camel_to_snake(self):
+        for (k, v) in EXPECTED_SNAKIFICATION.items():
+            self.assertEqual(_camel_to_snake(k), v)