Support nested messages, fix casing. Support test-cases in packages.

betterproto/casing.py

@@ -1,9 +1,21 @@
-import stringcase
+import re
+
+# Word delimiters and symbols that will not be preserved when re-casing.
+# language=PythonRegExp
+SYMBOLS = "[^a-zA-Z0-9]*"
+
+# Optionally capitalized word.
+# language=PythonRegExp
+WORD = "[A-Z]*[a-z]*[0-9]*"
+
+# Uppercase word, not followed by lowercase letters.
+# language=PythonRegExp
+WORD_UPPER = "[A-Z]+(?![a-z])[0-9]*"
 
 
 def safe_snake_case(value: str) -> str:
     """Snake case a value taking into account Python keywords."""
-    value = stringcase.snakecase(value)
+    value = snake_case(value)
     if value in [
         "and",
         "as",
@@ -39,3 +51,33 @@ def safe_snake_case(value: str) -> str:
         # https://www.python.org/dev/peps/pep-0008/#descriptive-naming-styles
         value += "_"
     return value
+
+
+def snake_case(value: str):
+    """
+    Join words with an underscore into lowercase and remove symbols.
+    """
+    snake = re.sub(
+        f"{SYMBOLS}({WORD_UPPER}|{WORD})", lambda groups: "_" + groups[1].lower(), value
+    )
+    return snake.strip("_")
+
+
+def pascal_case(value: str):
+    """
+    Capitalize each word and remove symbols.
+    """
+    return re.sub(
+        f"{SYMBOLS}({WORD_UPPER}|{WORD})", lambda groups: groups[1].capitalize(), value
+    )
+
+
+def camel_case(value: str):
+    """
+    Capitalize all words except first and remove symbols.
+    """
+    return capitalize_first(pascal_case(value))
+
+
+def capitalize_first(value: str):
+    return value[0:1].lower() + value[1:]