Fix convert_camel_case_to_snake

ariadne/utils.py

@@ -67,11 +67,15 @@ def convert_camel_case_to_snake(graphql_name: str) -> str:
                 i < max_index
                 and graphql_name[i] != c
                 and graphql_name[i + 1] == lowered_name[i + 1]
+                and graphql_name[i + 1] != "_"
             )
             # test134 -> test_134
-            or (c.isdigit() and not graphql_name[i - 1].isdigit())
+            or (
+                c.isdigit()
+                and not graphql_name[i - 1].isdigit()
+            )
             # 134test -> 134_test
-            or (not c.isdigit() and graphql_name[i - 1].isdigit())
+            or (not c.isdigit() and graphql_name[i] != "_" and graphql_name[i - 1].isdigit())
         ):
             python_name += "_"
         python_name += c

tests/test_camel_case_to_snake_case_convertion.py

@@ -42,6 +42,18 @@ def test_no_underscore_added_if_previous_character_is_an_underscore():
     assert convert_camel_case_to_snake("test__complexName") == "test__complex_name"
 
 
+@pytest.mark.parametrize(
+    ("test_str", "result"),
+    [
+        ("FOO_bar", "foo_bar"),
+        ("FOO_BAR", "foo_bar"),
+        ("S3_BUCKET", "s_3_bucket"),
+    ],
+)
+def test_no_underscore_added_if_next_character_is_an_underscore(test_str, result):
+    assert convert_camel_case_to_snake(test_str) == result
+
+
 def test_no_underscore_added_if_previous_character_is_uppercase():
     assert convert_camel_case_to_snake("testWithUPPERPart") == "test_with_upper_part"