Expose regex_engine flag

pydantic/_internal/_config.py

@@ -80,6 +80,7 @@ class ConfigWrapper:
     json_schema_serialization_defaults_required: bool
     json_schema_mode_override: Literal['validation', 'serialization', None]
     coerce_numbers_to_str: bool
+    regex_engine: Literal['rust-regex', 'python-re']
 
     def __init__(self, config: ConfigDict | dict[str, Any] | type[Any] | None, *, check: bool = True):
         if check:
@@ -176,6 +177,7 @@ def dict_not_none(**kwargs: Any) -> Any:
                 str_min_length=self.config_dict.get('str_min_length'),
                 hide_input_in_errors=self.config_dict.get('hide_input_in_errors'),
                 coerce_numbers_to_str=self.config_dict.get('coerce_numbers_to_str'),
+                regex_engine=self.config_dict.get('regex_engine'),
             )
         )
         return core_config
@@ -248,6 +250,7 @@ def _context_manager() -> Iterator[None]:
     json_schema_serialization_defaults_required=False,
     json_schema_mode_override=None,
     coerce_numbers_to_str=False,
+    regex_engine='rust-regex',
 )
 
 

pydantic/config.py

@@ -787,5 +787,38 @@ class Model(BaseModel):
     ```
     """
 
+    regex_engine: Literal['rust-regex', 'python-re']
+    """
+    The regex engine to used for pattern validation
+    Defaults to `'rust-regex'`.
+
+    - `rust-regex` uses the [`regex`](https://docs.rs/regex) Rust crate,
+      which is non-backtracking and therefore more DDoS resistant, but does not support all regex features.
+    - `python-re` use the [`re`](https://docs.python.org/3/library/re.html) module,
+      which supports all regex features, but may be slower.
+
+    ```py
+    from pydantic import BaseModel, ConfigDict, Field, ValidationError
+
+    class Model(BaseModel):
+        model_config = ConfigDict(regex_engine='python-re')
+
+        value: str = Field(pattern=r'^abc(?=def)')
+
+    print(Model(value='abcdef').value)
+    #> abcdef
+
+    try:
+        print(Model(value='abxyzcdef'))
+    except ValidationError as e:
+        print(e)
+        '''
+        1 validation error for Model
+        value
+          String should match pattern '^abc(?=def)' [type=string_pattern_mismatch, input_value='abxyzcdef', input_type=str]
+        '''
+    ```
+    """
+
 
 __getattr__ = getattr_migration(__name__)