feat: Make grpc transcode logic work in terms of protobuf python objects

google/api_core/path_template.py

@@ -176,18 +176,20 @@ def get_field(request, field):
     """Get the value of a field from a given dictionary.
 
     Args:
-        request (dict): A dictionary object.
+        request (dict | Message): A dictionary or a Message object.
         field (str): The key to the request in dot notation.
 
     Returns:
         The value of the field.
     """
     parts = field.split(".")
     value = request
+
     for part in parts:
         if not isinstance(value, dict):
-            return
-        value = value.get(part)
+            value = getattr(value, part, None)
+        else:
+            value = value.get(part)
     if isinstance(value, dict):
         return
     return value
@@ -197,19 +199,27 @@ def delete_field(request, field):
     """Delete the value of a field from a given dictionary.
 
     Args:
-        request (dict): A dictionary object.
+        request (dict | Message): A dictionary object or a Message.
         field (str): The key to the request in dot notation.
     """
     parts = deque(field.split("."))
     while len(parts) > 1:
-        if not isinstance(request, dict):
-            return
         part = parts.popleft()
-        request = request.get(part)
+        if not isinstance(request, dict):
+            if hasattr(request, part):
+                request = getattr(request, part, None)
+            else:
+                return
+        else:
+            request = request.get(part)
     part = parts.popleft()
     if not isinstance(request, dict):
-        return
-    request.pop(part, None)
+        if hasattr(request, part):
+            request.ClearField(part)
+        else:
+            return
+    else:
+        request.pop(part, None)
 
 
 def validate(tmpl, path):
@@ -237,7 +247,7 @@ def validate(tmpl, path):
     return True if re.match(pattern, path) is not None else False
 
 
-def transcode(http_options, **request_kwargs):
+def transcode(http_options, message=None, **request_kwargs):
     """Transcodes a grpc request pattern into a proper HTTP request following the rules outlined here,
     https://github.com/googleapis/googleapis/blob/master/google/api/http.proto#L44-L312
 
@@ -248,18 +258,20 @@ def transcode(http_options, **request_kwargs):
              'body'      (str): The body field name (optional)
              (This is a simplified representation of the proto option `google.api.http`)
 
+         message (Message) : A request object (optional)
          request_kwargs (dict) : A dict representing the request object
 
      Returns:
          dict: The transcoded request with these keys,
              'method'        (str)   : The http method
              'uri'           (str)   : The expanded uri
-             'body'          (dict)  : A dict representing the body (optional)
-             'query_params'  (dict)  : A dict mapping query parameter variables and values
+             'body'          (dict | Message)  : A dict or a Message representing the body (optional)
+             'query_params'  (dict | Message)  : A dict or Message mapping query parameter variables and values
 
      Raises:
          ValueError: If the request does not match the given template.
     """
+    transcoded_value = message or request_kwargs
     for http_option in http_options:
         request = {}
 
@@ -268,27 +280,35 @@ def transcode(http_options, **request_kwargs):
         path_fields = [
             match.group("name") for match in _VARIABLE_RE.finditer(uri_template)
         ]
-        path_args = {field: get_field(request_kwargs, field) for field in path_fields}
+        path_args = {field: get_field(transcoded_value, field) for field in path_fields}
         request["uri"] = expand(uri_template, **path_args)
-        # Remove fields used in uri path from request
-        leftovers = copy.deepcopy(request_kwargs)
-        for path_field in path_fields:
-            delete_field(leftovers, path_field)
 
         if not validate(uri_template, request["uri"]) or not all(path_args.values()):
             continue
 
+        # Remove fields used in uri path from request
+        leftovers = copy.deepcopy(transcoded_value)
+        for path_field in path_fields:
+            delete_field(leftovers, path_field)
+
         # Assign body and query params
         body = http_option.get("body")
 
         if body:
             if body == "*":
                 request["body"] = leftovers
-                request["query_params"] = {}
+                if message:
+                    request["query_params"] = message.__class__()
+                else:
+                    request["query_params"] = {}
             else:
                 try:
-                    request["body"] = leftovers.pop(body)
-                except KeyError:
+                    if message:
+                        request["body"] = getattr(leftovers, body)
+                        delete_field(leftovers, body)
+                    else:
+                        request["body"] = leftovers.pop(body)
+                except (KeyError, AttributeError):
                     continue
                 request["query_params"] = leftovers
         else: