Fix regex handling and add related tests

Author: kmoyashi

src/drf_pydantic/parse.py

@@ -358,7 +358,7 @@ def _convert_type(  # noqa: PLR0911
         if issubclass(type_, pydantic.BaseModel):
             return create_serializer_from_model(type_, drf_config=drf_config)(**kwargs)
         # Decimal
-        elif type_ is decimal.Decimal:
+        if type_ is decimal.Decimal:
             _context = decimal.getcontext()
             kwargs["max_digits"] = kwargs.get("max_digits", None) or _context.prec
             kwargs["decimal_places"] = (
@@ -367,7 +367,11 @@ def _convert_type(  # noqa: PLR0911
             return serializers.DecimalField(**kwargs)
         # Regex
         elif field is not None and any(
-            isinstance(item, pydantic.StringConstraints) and item.pattern is not None
+            (isinstance(item, pydantic.StringConstraints) and item.pattern is not None)
+            or (
+                isinstance(item, PydanticMetadata)
+                and getattr(item, "pattern", None) is not None
+            )
             for item in field.metadata
         ):
             regex_patterns: List[Union[str, re.Pattern[str]]] = []
@@ -377,6 +381,11 @@ def _convert_type(  # noqa: PLR0911
                     and item.pattern is not None
                 ):
                     regex_patterns.append(item.pattern)
+                elif (
+                    isinstance(item, PydanticMetadata)
+                    and getattr(item, "pattern", None) is not None
+                ):
+                    regex_patterns.append(getattr(item, "pattern"))
             if len(regex_patterns) > 1:
                 raise FieldConversionError(
                     f"Field has multiple regex patterns: {regex_patterns}"

tests/test_fields.py

@@ -105,6 +105,41 @@ class Person(BaseModel):
         )
         assert serializer.fields["phone_number"].allow_null is False
 
+    def test_regex_from_field(self):
+        pattern = r"^\+?[0-9]+$"
+
+        class Person(BaseModel):
+            phone_number: typing.Annotated[
+                str,
+                pydantic.Field(pattern=pattern),
+            ]
+
+        serializer = Person.drf_serializer()
+
+        assert isinstance(serializer.fields["phone_number"], serializers.RegexField)
+        assert serializer.fields["phone_number"].validators[-1].regex == re.compile(
+            pattern
+        )
+        assert serializer.fields["phone_number"].allow_null is False
+
+    def test_compiled_regex(self):
+        pattern = r"^\+?[0-9]+$"
+        compiled_pattern = re.compile(pattern)
+
+        class Person(BaseModel):
+            phone_number: typing.Annotated[
+                str,
+                pydantic.StringConstraints(pattern=compiled_pattern),
+            ]
+
+        serializer = Person.drf_serializer()
+
+        assert isinstance(serializer.fields["phone_number"], serializers.RegexField)
+        assert serializer.fields["phone_number"].validators[-1].regex == re.compile(
+            pattern
+        )
+        assert serializer.fields["phone_number"].allow_null is False
+
     def test_optional_regex(self):
         pattern = r"^\+?[0-9]+$"
 
@@ -137,6 +172,21 @@ class Person(BaseModel):
         assert "Error when converting model: Person" in str(exc_info.value)
         assert "Field has multiple regex patterns" in str(exc_info.value)
 
+    def test_multiple_regex_with_field_error(self):
+        with pytest.raises(ModelConversionError) as exc_info:
+
+            class Person(BaseModel):
+                phone_number: typing.Annotated[
+                    str,
+                    pydantic.StringConstraints(pattern=r"123"),
+                    pydantic.Field(pattern=r"456"),
+                ]
+
+            Person.drf_serializer()
+
+        assert "Error when converting model: Person" in str(exc_info.value)
+        assert "Field has multiple regex patterns" in str(exc_info.value)
+
     def test_url(self):
         class Person(BaseModel):
             website: pydantic.HttpUrl