feat: add default encoder for Pattern type (#2056)

closes #2045

changes/2045-PrettyWood.md

@@ -0,0 +1 @@
+add default encoder for `Pattern` type

pydantic/json.py

@@ -5,7 +5,7 @@
 from ipaddress import IPv4Address, IPv4Interface, IPv4Network, IPv6Address, IPv6Interface, IPv6Network
 from pathlib import Path
 from types import GeneratorType
-from typing import Any, Callable, Dict, Type, Union
+from typing import Any, Callable, Dict, Pattern, Type, Union
 from uuid import UUID
 
 from .color import Color
@@ -54,6 +54,9 @@ def pydantic_encoder(obj: Any) -> Any:
     elif is_dataclass(obj):
         return asdict(obj)
 
+    if isinstance(obj, Pattern):
+        return obj.pattern
+
     # Check the class type and its superclasses for a matching encoder
     for base in obj.__class__.__mro__[:-1]:
         try:

tests/test_json.py

@@ -1,5 +1,6 @@
 import datetime
 import json
+import re
 import sys
 from dataclasses import dataclass as vanilla_dataclass
 from decimal import Decimal
@@ -51,6 +52,7 @@ class MyEnum(Enum):
         (Decimal('12.34'), '12.34'),
         (create_model('BarModel', a='b', c='d')(), '{"a": "b", "c": "d"}'),
         (MyEnum.foo, '"bar"'),
+        (re.compile('^regex$'), '"^regex$"'),
     ],
 )
 def test_encoding(input, output):