fix: Warn instead of crashing when schema helpers cannot append `null…

…` to types (#1970)

* Add failing test

* Warn instead of crashing

---------

Co-authored-by: Ken Payne <ken@meltano.com>

singer_sdk/helpers/_typing.py

@@ -4,21 +4,21 @@
 
 import copy
 import datetime
+import logging
 import typing as t
 from enum import Enum
 from functools import lru_cache
 
 import pendulum
 
-if t.TYPE_CHECKING:
-    import logging
-
 _MAX_TIMESTAMP = "9999-12-31 23:59:59.999999"
 _MAX_TIME = "23:59:59.999999"
 JSONSCHEMA_ANNOTATION_SECRET = "secret"  # noqa: S105
 JSONSCHEMA_ANNOTATION_WRITEONLY = "writeOnly"
 UTC = datetime.timezone.utc
 
+logger = logging.getLogger(__name__)
+
 
 class DatetimeErrorTreatmentEnum(Enum):
     """Enum for treatment options for date parsing error."""
@@ -67,11 +67,12 @@ def append_type(type_dict: dict, new_type: str) -> dict:
             result["type"] = [*type_array, new_type]
         return result
 
-    msg = (
+    logger.warning(
         "Could not append type because the JSON schema for the dictionary "
-        f"`{type_dict}` appears to be invalid."
+        "`%s` appears to be invalid.",
+        type_dict,
     )
-    raise ValueError(msg)
+    return result
 
 
 def is_secret_type(type_dict: dict) -> bool:

singer_sdk/typing.py

@@ -493,6 +493,26 @@ def type_dict(self) -> dict:  # type: ignore[override]
         return {"type": "array", "items": self.wrapped_type.type_dict, **self.extras}
 
 
+class AnyType(JSONTypeHelper):
+    """Any type."""
+
+    def __init__(
+        self,
+        *args: t.Any,
+        **kwargs: t.Any,
+    ) -> None:
+        super().__init__(*args, **kwargs)
+
+    @DefaultInstanceProperty
+    def type_dict(self) -> dict:
+        """Get type dictionary.
+
+        Returns:
+            A dictionary describing the type.
+        """
+        return {**self.extras}
+
+
 class Property(JSONTypeHelper[T], t.Generic[T]):
     """Generic Property. Should be nested within a `PropertiesList`."""
 

tests/core/test_jsonschema_helpers.py

@@ -4,6 +4,7 @@
 
 import re
 import typing as t
+from logging import WARNING
 from textwrap import dedent
 
 import pytest
@@ -26,6 +27,7 @@
 )
 from singer_sdk.tap_base import Tap
 from singer_sdk.typing import (
+    AnyType,
     ArrayType,
     BooleanType,
     CustomType,
@@ -130,6 +132,26 @@ def test_to_json():
     )
 
 
+def test_any_type(caplog: pytest.LogCaptureFixture):
+    schema = PropertiesList(
+        Property("any_type", AnyType, description="Can be anything"),
+    )
+    with caplog.at_level(WARNING):
+        assert schema.to_dict() == {
+            "type": "object",
+            "properties": {
+                "any_type": {
+                    "description": "Can be anything",
+                },
+            },
+        }
+        assert caplog.records[0].levelname == "WARNING"
+        assert caplog.records[0].message == (
+            "Could not append type because the JSON schema for the dictionary `{}` "
+            "appears to be invalid."
+        )
+
+
 def test_nested_complex_objects():
     test1a = Property(
         "Datasets",