From f8d7dfec4c7e15e6acebcaf7c7019042d8de33be Mon Sep 17 00:00:00 2001
From: Ruben DI BATTISTA <ruben.di_battista@qube-rt.com>
Date: Mon, 24 Jan 2022 01:33:57 +0100
Subject: [PATCH] Strip empty fields in MultipartEncoder

This is coherent with what's done in requests
---
 requests_toolbelt/multipart/encoder.py |  2 ++
 tests/test_multipart_encoder.py        | 25 ++++++++++++++++++++-----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/requests_toolbelt/multipart/encoder.py b/requests_toolbelt/multipart/encoder.py
index 2d539617..a05585f6 100644
--- a/requests_toolbelt/multipart/encoder.py
+++ b/requests_toolbelt/multipart/encoder.py
@@ -227,6 +227,8 @@ def _iter_fields(self):
                     file_name, file_pointer, file_type = v
                 else:
                     file_name, file_pointer, file_type, file_headers = v
+            elif v is None:
+                continue
             else:
                 file_pointer = v
 
diff --git a/tests/test_multipart_encoder.py b/tests/test_multipart_encoder.py
index 575f54c4..c8351e23 100644
--- a/tests/test_multipart_encoder.py
+++ b/tests/test_multipart_encoder.py
@@ -1,14 +1,17 @@
 # -*- coding: utf-8 -*-
-import unittest
 import io
+import unittest
 
 import requests
-
-from requests_toolbelt.multipart.encoder import (
-    CustomBytesIO, MultipartEncoder, FileFromURLWrapper, FileNotSupportedError)
 from requests_toolbelt._compat import filepost
-from . import get_betamax
+from requests_toolbelt.multipart.encoder import (
+    CustomBytesIO,
+    FileFromURLWrapper,
+    FileNotSupportedError,
+    MultipartEncoder,
+)
 
+from . import get_betamax
 
 preserve_bytes = {'preserve_exact_body_bytes': True}
 
@@ -272,6 +275,18 @@ def test_regression_2(self):
 
         assert read_so_far == total_size
 
+    def test_empty_files_key(self):
+        """Ensure empty `fields` keys are stripped from the request"""
+
+        fields = {
+            "test": "this is a test", 
+            "empty": None
+        }
+
+        m = MultipartEncoder(fields=fields)
+
+        assert len(m.parts) == 1
+
     def test_handles_empty_unicode_values(self):
         """Verify that the Encoder can handle empty unicode strings.