- The precision used when coercing a returned floating point value to

Python ``Decimal`` via string is now configurable.  The
flag ``decimal_return_scale`` is now supported by all :class:`.Numeric`
and :class:`.Float` types, which will ensure this many digits are taken
from the native floating point value when it is converted to string.
If not present, the type will make use of the value of ``.scale``, if
the type supports this setting and it is non-None.  Otherwise the original
default length of 10 is used. [ticket:2867]

2 files changed, 18 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/requirements.py b/lib/sqlalchemy/testing/requirements.py
index 408c3705e..e48fa2c00 100644
--- a/lib/sqlalchemy/testing/requirements.py
+++ b/lib/sqlalchemy/testing/requirements.py
@@ -394,6 +394,14 @@ class SuiteRequirements(Requirements):
         return exclusions.closed()
 
     @property
+    def precision_generic_float_type(self):
+        """target backend will return native floating point numbers with at
+        least seven decimal places when using the generic Float type.
+
+        """
+        return exclusions.open()
+
+    @property
     def floats_to_four_decimals(self):
         """target backend can return a floating-point number with four
         significant digits (such as 15.7563) accurately
diff --git a/lib/sqlalchemy/testing/suite/test_types.py b/lib/sqlalchemy/testing/suite/test_types.py
index 3eb105ba3..b147f891a 100644
--- a/lib/sqlalchemy/testing/suite/test_types.py
+++ b/lib/sqlalchemy/testing/suite/test_types.py
@@ -356,6 +356,16 @@ class NumericTest(_LiteralRoundTripFixture, fixtures.TestBase):
             filter_=lambda n: n is not None and round(n, 5) or None
         )
 
+
+    @testing.requires.precision_generic_float_type
+    def test_float_custom_scale(self):
+        self._do_test(
+            Float(None, decimal_return_scale=7, asdecimal=True),
+            [15.7563827, decimal.Decimal("15.7563827")],
+            [decimal.Decimal("15.7563827"),],
+            check_scale=True
+        )
+
     def test_numeric_as_decimal(self):
         self._do_test(
             Numeric(precision=8, scale=4),