DecimalRangeField __contains query for a value causes DataError

[Trent Holliday]

With a model of:

class Thing(models.Model):
    decimal_range = DecimalRangeField()

Attempting to query against the decimal range field using a value instead of a range of values leads to the below error being raised.

>>> list(Thing.objects.filter(decimal_range__contains=199))
Traceback (most recent call last):
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)
psycopg2.errors.InvalidTextRepresentation: invalid input syntax for type integer: "none"
LINE 1: ...HERE "contractor_thing"."decimal_range" @> (199)::numeric(No...
                                                             ^


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/opt/homebrew/Cellar/python@3.10/3.10.14_1/Frameworks/Python.framework/Versions/3.10/lib/python3.10/code.py", line 90, in runcode
    exec(code, self.locals)
  File "<console>", line 1, in <module>
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/models/query.py", line 398, in __iter__
    self._fetch_all()
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/models/query.py", line 1881, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/models/query.py", line 91, in __iter__
    results = compiler.execute_sql(
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 1562, in execute_sql
    cursor.execute(sql, params)
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 102, in execute
    return super().execute(sql, params)
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/cachalot/monkey_patch.py", line 137, in inner
    return original(cursor, sql, *args, **kwargs)
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/sentry_sdk/integrations/django/__init__.py", line 644, in execute
    result = real_execute(self, sql, params)
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 67, in execute
    return self._execute_with_wrappers(
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 80, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 84, in _execute
    with self.db.wrap_database_errors:
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/utils.py", line 91, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/Users/tholliday/code/ADMS/backend/.venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)
django.db.utils.DataError: invalid input syntax for type integer: "none"
LINE 1: ...HERE "contractor_thing"."decimal_range" @> (199)::numeric(No...

I've done some digging to try and identify why this is happening. From what I can tell, when the DecimalRangeField gets intialized, self.base_field is a DecimalField and gets instantiated with decimal_places and max_digits set to None, ​https://github.com/django/django/blame/fcd9d08379a2aee3b2c49eab0d0b8db6fd66d091/django/contrib/postgres/fields/ranges.py#L65. Then when the Cast operation happens for the RangeContains lookup here: ​https://github.com/django/django/blame/fcd9d08379a2aee3b2c49eab0d0b8db6fd66d091/django/contrib/postgres/fields/ranges.py#L215 it results in passing in the None values for the precision and scale.