From 682dbbe4bb3c397558889bfdf77ac6102be02344 Mon Sep 17 00:00:00 2001
From: Fernando Cezar Bernardelli <fernando@brainbot.com>
Date: Fri, 9 Jul 2021 14:50:38 +0200
Subject: [PATCH] remove null fields from response

---
 raiden/messages/metadata.py                   | 30 +++++++++++--------
 .../serialized_messages/LockedTransfer.json   |  3 +-
 .../serialized_messages/RefundTransfer.json   |  1 -
 3 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/raiden/messages/metadata.py b/raiden/messages/metadata.py
index 5a200f9b8e1..8157f61ce64 100644
--- a/raiden/messages/metadata.py
+++ b/raiden/messages/metadata.py
@@ -1,5 +1,5 @@
 from copy import deepcopy
-from dataclasses import dataclass, field
+from dataclasses import dataclass
 from typing import Any
 
 import canonicaljson
@@ -79,7 +79,7 @@ class Metadata:
     # inititally create the Metadata object as part of a message - this is the case when we are
     # the initiator of a transfer.
     original_data: Optional[Any] = None
-    encrypted_secret: Optional[EncryptedSecret] = field(default=None, repr=False)
+    encrypted_secret: Optional[EncryptedSecret] = None
 
     class Meta:
         """
@@ -89,6 +89,7 @@ class Meta:
         """
 
         unknown = EXCLUDE
+        serialize_missing = False
 
     @cached_property
     def hash(self) -> bytes:
@@ -102,18 +103,23 @@ def _post_load(  # pylint: disable=no-self-use,unused-argument
         return data
 
     @post_dump(pass_many=True)
-    def _post_dump(  # pylint: disable=no-self-use,unused-argument
+    def _post_dump(  # pylint: disable=unused-argument
         self, data: Dict[str, Any], many: bool
     ) -> Dict[str, Any]:
-        original_data = data.pop("original_data", {})
-        if original_data:
-            # We received the metadata (Mediator/Target) and read in the data
-            # for internal processing,
-            # so once we pass them to the next node just dump the data exactly as we received them
-            return original_data
-        # We initially created the Metadata (Initiator),
-        # so dump the known fields as per the Schema
-        return data
+        """
+        `original_data` means we received the metadata (Mediator/Target) and read in the data
+        for internal processing, so once we pass them to the next node just dump the data exactly
+        as we received them.
+
+        Returning `data` means we initially created the Metadata (Initiator), so dump the known
+        fields as per the Schema
+        """
+        dumped_data = data.pop("original_data", None) or data
+
+        if not self.Meta.serialize_missing:
+            dumped_data = {k: v for k, v in dumped_data.items() if v is not None}
+
+        return dumped_data
 
     def __repr__(self) -> str:
         return f"Metadata: routes: {[repr(route) for route in self.routes]}"
diff --git a/raiden/tests/unit/serialized_messages/LockedTransfer.json b/raiden/tests/unit/serialized_messages/LockedTransfer.json
index 6bf3dc10865..fc97b27f38d 100644
--- a/raiden/tests/unit/serialized_messages/LockedTransfer.json
+++ b/raiden/tests/unit/serialized_messages/LockedTransfer.json
@@ -11,7 +11,6 @@
     "locksroot": "0x07fe6255272aa923234b651199a2d7a277e3b1af3156f18c3bc0ba45d27fa380",
     "message_identifier": "1",
     "metadata": {
-        "encrypted_secret": null,
         "routes": [
             {
                 "route": [
@@ -24,7 +23,7 @@
     "nonce": "1",
     "payment_identifier": "1",
     "recipient": "0x7461726765747461726765747461726765747461",
-    "signature": "0xdae92f24535a87229b04f79d4f419cfd2263a7c27e815194d9fc91cc9d13cbc27108480cbf6a9aa502e36cec23a79cdabc126356dcd76e2631f1b6eb6eaa94611c",
+    "signature": "0xcf304f3401934837830cff2086a29987eb7035bdfec12b1c73de8793625f982b4ec35504cc40db951ed8eebb44123a87679a615300177858babd950b2da3e4391b",
     "target": "0x7461726765747461726765747461726765747461",
     "token": "0x746f6b656e746f6b656e746f6b656e746f6b656e",
     "token_network_address": "0x6e6574776f726b6e6574776f726b6e6574776f72",
diff --git a/raiden/tests/unit/serialized_messages/RefundTransfer.json b/raiden/tests/unit/serialized_messages/RefundTransfer.json
index e1314406973..3a330d86fea 100644
--- a/raiden/tests/unit/serialized_messages/RefundTransfer.json
+++ b/raiden/tests/unit/serialized_messages/RefundTransfer.json
@@ -11,7 +11,6 @@
     "locksroot": "0x07fe6255272aa923234b651199a2d7a277e3b1af3156f18c3bc0ba45d27fa380",
     "message_identifier": "1",
     "metadata": {
-        "encrypted_secret": null,
         "routes": [
             {
                 "route": [