PyMySQL already rejects non-finite float parameters before sending SQL, but equivalent decimal.Decimal values were still serialized and sent. This change aligns Decimal behavior with existing float safeguards for unsupported non-finite numeric parameters.

• Converter behavior

  • Updated pymysql.converters.Decimal2Literal to reject non-finite Decimal values via Decimal.is_finite().
  • Non-finite values now raise ProgrammingError with the same message pattern already used for float ("<value> can not be used with MySQL"), normalized to lowercase.

• Targeted test coverage

  • Added converter-level tests in pymysql/tests/test_converters.py for:
    • Decimal("NaN")
    • Decimal("sNaN")
    • Decimal("Infinity")
    • Decimal("-Infinity")
  • Each case asserts ProgrammingError is raised during literal conversion.

• Example

  from decimal import Decimal
  from pymysql import converters
  
  converters.Decimal2Literal(Decimal("NaN"), None)
  # raises ProgrammingError: nan can not be used with MySQL