From d4608a00cf4855021dfb1a780556e24dedc94b14 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebasti=C3=A1n=20Ram=C3=ADrez?= <tiangolo@gmail.com>
Date: Sun, 23 Jan 2022 17:32:04 +0100
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Prefer=20custom=20encoder=20over?=
 =?UTF-8?q?=20defaults=20if=20specified=20in=20`jsonable=5Fencoder`=20(#44?=
 =?UTF-8?q?67)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Vivek Sunder <sviveksunder@gmail.com>
---
 fastapi/encoders.py            | 18 +++++++++---------
 tests/test_jsonable_encoder.py | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/fastapi/encoders.py b/fastapi/encoders.py
index 3f599c9fa..4b7ffe313 100644
--- a/fastapi/encoders.py
+++ b/fastapi/encoders.py
@@ -34,9 +34,17 @@ def jsonable_encoder(
     exclude_unset: bool = False,
     exclude_defaults: bool = False,
     exclude_none: bool = False,
-    custom_encoder: Dict[Any, Callable[[Any], Any]] = {},
+    custom_encoder: Optional[Dict[Any, Callable[[Any], Any]]] = None,
     sqlalchemy_safe: bool = True,
 ) -> Any:
+    custom_encoder = custom_encoder or {}
+    if custom_encoder:
+        if type(obj) in custom_encoder:
+            return custom_encoder[type(obj)](obj)
+        else:
+            for encoder_type, encoder_instance in custom_encoder.items():
+                if isinstance(obj, encoder_type):
+                    return encoder_instance(obj)
     if include is not None and not isinstance(include, (set, dict)):
         include = set(include)
     if exclude is not None and not isinstance(exclude, (set, dict)):
@@ -118,14 +126,6 @@ def jsonable_encoder(
             )
         return encoded_list
 
-    if custom_encoder:
-        if type(obj) in custom_encoder:
-            return custom_encoder[type(obj)](obj)
-        else:
-            for encoder_type, encoder in custom_encoder.items():
-                if isinstance(obj, encoder_type):
-                    return encoder(obj)
-
     if type(obj) in ENCODERS_BY_TYPE:
         return ENCODERS_BY_TYPE[type(obj)](obj)
     for encoder, classes_tuple in encoders_by_class_tuples.items():
diff --git a/tests/test_jsonable_encoder.py b/tests/test_jsonable_encoder.py
index e2aa8adf8..fa82b5ea8 100644
--- a/tests/test_jsonable_encoder.py
+++ b/tests/test_jsonable_encoder.py
@@ -161,6 +161,21 @@ def test_custom_encoders():
     assert encoded_instance["dt_field"] == instance.dt_field.isoformat()
 
 
+def test_custom_enum_encoders():
+    def custom_enum_encoder(v: Enum):
+        return v.value.lower()
+
+    class MyEnum(Enum):
+        ENUM_VAL_1 = "ENUM_VAL_1"
+
+    instance = MyEnum.ENUM_VAL_1
+
+    encoded_instance = jsonable_encoder(
+        instance, custom_encoder={MyEnum: custom_enum_encoder}
+    )
+    assert encoded_instance == custom_enum_encoder(instance)
+
+
 def test_encode_model_with_path(model_with_path):
     if isinstance(model_with_path.path, PureWindowsPath):
         expected = "\\foo\\bar"