From b6f4158f2df68fd57016dc3f0ec04e73ca3d334c Mon Sep 17 00:00:00 2001
From: yuval <yuval.poleg@placer.ai>
Date: Tue, 7 Nov 2023 19:47:30 +0200
Subject: [PATCH] if default value is callable, call it, also, verify that the
 default value is serializable

---
 marshmallow_jsonschema/base.py | 17 +++++++++++++++--
 tests/test_dump.py             | 11 +++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/marshmallow_jsonschema/base.py b/marshmallow_jsonschema/base.py
index 2db5a3d..5744dc6 100644
--- a/marshmallow_jsonschema/base.py
+++ b/marshmallow_jsonschema/base.py
@@ -1,5 +1,6 @@
 import datetime
 import decimal
+import json
 import uuid
 from enum import Enum
 from inspect import isclass
@@ -195,8 +196,13 @@ def _from_python_type(self, obj, field, pytype) -> typing.Dict[str, typing.Any]:
         if field.dump_only:
             json_schema["readOnly"] = True
 
-        if field.default is not missing and not callable(field.default):
-            json_schema["default"] = field.default
+        if field.default is not missing:
+            if (not callable(field.default) and self._is_serializable(field.default)):
+                json_schema["default"] = field.default
+            else:
+                default_value = field.default()
+                if self._is_serializable(default_value):
+                    json_schema["default"] = default_value
 
         if ALLOW_ENUMS and isinstance(field, EnumField):
             json_schema["enum"] = self._get_enum_values(field)
@@ -225,6 +231,13 @@ def _from_python_type(self, obj, field, pytype) -> typing.Dict[str, typing.Any]:
             )
         return json_schema
 
+    def _is_serializable(self, value):
+        try:
+            json.dumps(value)
+            return True
+        except TypeError:
+            return False
+
     def _get_enum_values(self, field) -> typing.List[str]:
         assert ALLOW_ENUMS and isinstance(field, EnumField)
 
diff --git a/tests/test_dump.py b/tests/test_dump.py
index 38584f5..6a0a0b6 100644
--- a/tests/test_dump.py
+++ b/tests/test_dump.py
@@ -42,6 +42,17 @@ class TestSchema(Schema):
     props = dumped["definitions"]["TestSchema"]["properties"]
     assert "default" not in props["uid"]
 
+def test_default_callable_serialized():
+    class TestSchema(Schema):
+        uid = fields.UUID(default=lambda: str(uuid.uuid4()))
+
+    schema = TestSchema()
+
+    dumped = validate_and_dump(schema)
+
+    props = dumped["definitions"]["TestSchema"]["properties"]
+    assert "default" in props["uid"]
+
 
 def test_uuid():
     schema = UserSchema()