fix(schema): add basic support of Pattern type in schema generation

closes #1767

changes/1767-PrettyWood.md

@@ -0,0 +1 @@
+add basic support of Pattern type in schema generation

docs/build/schema_mapping.py

@@ -145,6 +145,13 @@
         'JSON Schema Validation',
         ''
     ],
+    [
+        'Pattern',
+        'string',
+        {'format': 'regex'},
+        'JSON Schema Validation',
+        ''
+    ],
     [
         'bytes',
         'string',

pydantic/schema.py

@@ -14,6 +14,7 @@
     Iterable,
     List,
     Optional,
+    Pattern,
     Sequence,
     Set,
     Tuple,
@@ -618,6 +619,7 @@ def field_singleton_sub_fields_schema(
     (IPv6Interface, {'type': 'string', 'format': 'ipv6interface'}),
     (IPv4Address, {'type': 'string', 'format': 'ipv4'}),
     (IPv6Address, {'type': 'string', 'format': 'ipv6'}),
+    (Pattern, {'type': 'string', 'format': 'regex'}),
     (str, {'type': 'string'}),
     (bytes, {'type': 'string', 'format': 'binary'}),
     (bool, {'type': 'boolean'}),
@@ -643,7 +645,7 @@ def add_field_type_to_schema(field_type: Any, schema: Dict[str, Any]) -> None:
     and then modifies the given `schema` with the information from that type.
     """
     for type_, t_schema in field_class_to_schema:
-        if issubclass(field_type, type_):
+        if lenient_issubclass(field_type, type_):
             schema.update(t_schema)
             break
 
@@ -716,7 +718,7 @@ def field_singleton_schema(  # noqa: C901 (ignore complexity)
     if lenient_issubclass(getattr(field_type, '__pydantic_model__', None), BaseModel):
         field_type = field_type.__pydantic_model__
 
-    if issubclass(field_type, BaseModel):
+    if lenient_issubclass(field_type, BaseModel):
         model_name = model_name_map[field_type]
         if field_type not in known_models:
             sub_schema, sub_definitions, sub_nested_models = model_process_schema(

pydantic/utils.py

@@ -12,6 +12,7 @@
     List,
     Mapping,
     Optional,
+    Pattern,
     Set,
     Tuple,
     Type,
@@ -104,7 +105,8 @@ def validate_field_name(bases: List[Type['BaseModel']], field_name: str) -> None
 
 
 def lenient_issubclass(cls: Any, class_or_tuple: Union[Type[Any], Tuple[Type[Any], ...]]) -> bool:
-    return isinstance(cls, type) and issubclass(cls, class_or_tuple)
+    """Fallback for `typing.Pattern` as it is not a valid class"""
+    return isinstance(cls, type) and issubclass(cls, class_or_tuple) or cls is class_or_tuple is Pattern
 
 
 def in_ipython() -> bool:

tests/test_types.py

@@ -2055,6 +2055,13 @@ class Foobar(BaseModel):
     f2 = Foobar(pattern=p)
     assert f2.pattern is p
 
+    assert Foobar.schema() == {
+        'type': 'object',
+        'title': 'Foobar',
+        'properties': {'pattern': {'type': 'string', 'format': 'regex', 'title': 'Pattern'}},
+        'required': ['pattern'],
+    }
+
 
 def test_pattern_error():
     class Foobar(BaseModel):