[cloud] Improve snake <-> camel conversion for AWS utils (#31400)

Allow CamelCase version of snake_dict_to_camel_dict
(currently only dromedaryCase is supported)

Add reversible option to camel_dict_to_snake_dict

Add tests for both of these options

lib/ansible/module_utils/ec2.py

@@ -343,19 +343,26 @@ def ec2_connect(module):
     return ec2
 
 
-def _camel_to_snake(name):
+def _camel_to_snake(name, reversible=False):
 
     def prepend_underscore_and_lower(m):
         return '_' + m.group(0).lower()
 
     import re
+    if reversible:
+        upper_pattern = r'[A-Z]'
+    else:
         # Cope with pluralized abbreviations such as TargetGroupARNs
         # that would otherwise be rendered target_group_ar_ns
-    plural_pattern = r'[A-Z]{3,}s$'
-    s1 = re.sub(plural_pattern, prepend_underscore_and_lower, name)
+        upper_pattern = r'[A-Z]{3,}s$'
+
+    s1 = re.sub(upper_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:]
+    if reversible:
+        return s1
+
     # 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]+)'
@@ -363,14 +370,22 @@ def _camel_to_snake(name):
     return re.sub(all_cap_pattern, r'\1_\2', s2).lower()
 
 
-def camel_dict_to_snake_dict(camel_dict):
+def camel_dict_to_snake_dict(camel_dict, reversible=False):
+    """
+    reversible allows two way conversion of a camelized dict
+    such that snake_dict_to_camel_dict(camel_dict_to_snake_dict(x)) == x
+
+    This is achieved through mapping e.g. HTTPEndpoint to h_t_t_p_endpoint
+    where the default would be simply http_endpoint, which gets turned into
+    HttpEndpoint if recamelized.
+    """
 
     def value_is_list(camel_list):
 
         checked_list = []
         for item in camel_list:
             if isinstance(item, dict):
-                checked_list.append(camel_dict_to_snake_dict(item))
+                checked_list.append(camel_dict_to_snake_dict(item, reversible))
             elif isinstance(item, list):
                 checked_list.append(value_is_list(item))
             else:
@@ -381,35 +396,44 @@ 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, reversible=reversible)] = camel_dict_to_snake_dict(v, reversible)
         elif isinstance(v, list):
-            snake_dict[_camel_to_snake(k)] = value_is_list(v)
+            snake_dict[_camel_to_snake(k, reversible=reversible)] = value_is_list(v)
         else:
-            snake_dict[_camel_to_snake(k)] = v
+            snake_dict[_camel_to_snake(k, reversible=reversible)] = v
 
     return snake_dict
 
 
-def snake_dict_to_camel_dict(snake_dict):
+def _snake_to_camel(snake, capitalize_first=False):
+    if capitalize_first:
+        return ''.join(x.capitalize() or '_' for x in snake.split('_'))
+    else:
+        return snake.split('_')[0] + ''.join(x.capitalize() or '_' for x in snake.split('_')[1:])
+
+
+def snake_dict_to_camel_dict(snake_dict, capitalize_first=False):
+    """
+    Perhaps unexpectedly, snake_dict_to_camel_dict returns dromedaryCase
+    rather than true CamelCase. Passing capitalize_first=True returns
+    CamelCase. The default remains False as that was the original implementation
+    """
 
-    def camelize(complex_type):
+    def camelize(complex_type, capitalize_first=False):
         if complex_type is None:
             return
         new_type = type(complex_type)()
         if isinstance(complex_type, dict):
             for key in complex_type:
-                new_type[camel(key)] = camelize(complex_type[key])
+                new_type[_snake_to_camel(key, capitalize_first)] = camelize(complex_type[key], capitalize_first)
         elif isinstance(complex_type, list):
             for i in range(len(complex_type)):
-                new_type.append(camelize(complex_type[i]))
+                new_type.append(camelize(complex_type[i], capitalize_first))
         else:
             return complex_type
         return new_type
 
-    def camel(words):
-        return words.split('_')[0] + ''.join(x.capitalize() or '_' for x in words.split('_')[1:])
-
-    return camelize(snake_dict)
+    return camelize(snake_dict, capitalize_first)
 
 
 def ansible_dict_to_boto3_filter_list(filters_dict):

test/units/module_utils/ec2/test_camel_to_snake.py

@@ -17,7 +17,7 @@
 # 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
+from ansible.module_utils.ec2 import _camel_to_snake, _snake_to_camel
 
 EXPECTED_SNAKIFICATION = {
     'alllower': 'alllower',
@@ -29,9 +29,35 @@ EXPECTED_SNAKIFICATION = {
     'PLURALs': 'plurals'
 }
 
+EXPECTED_REVERSIBLE = {
+    'TwoWords': 'two_words',
+    'AllUpperAtEND': 'all_upper_at_e_n_d',
+    'AllUpperButPLURALs': 'all_upper_but_p_l_u_r_a_ls',
+    'TargetGroupARNs': 'target_group_a_r_ns',
+    'HTTPEndpoints': 'h_t_t_p_endpoints',
+    'PLURALs': 'p_l_u_r_a_ls'
+}
+
 
 class CamelToSnakeTestCase(unittest.TestCase):
 
     def test_camel_to_snake(self):
         for (k, v) in EXPECTED_SNAKIFICATION.items():
             self.assertEqual(_camel_to_snake(k), v)
+
+    def test_reversible_camel_to_snake(self):
+        for (k, v) in EXPECTED_REVERSIBLE.items():
+            self.assertEqual(_camel_to_snake(k, reversible=True), v)
+
+
+class SnakeToCamelTestCase(unittest.TestCase):
+
+    def test_snake_to_camel_reversed(self):
+        for (k, v) in EXPECTED_REVERSIBLE.items():
+            self.assertEqual(_snake_to_camel(v, capitalize_first=True), k)
+
+
+class CamelToSnakeAndBackTestCase(unittest.TestCase):
+    def test_camel_to_snake_and_back(self):
+        for (k, v) in EXPECTED_REVERSIBLE.items():
+            self.assertEqual(_snake_to_camel(_camel_to_snake(k, reversible=True), capitalize_first=True), k)