Fix numeric bug (piccolo-orm#236)

* fixed the bug discussed in piccolo-orm#232 .
if precision and scale are not set for the Numeric Field, 'None' value will be returned.

* added a unit test for testing the bug-fix

* fixed lint issues

* add type annotations for precision and scale

Co-authored-by: Daniel Townsend <[email protected]>

Author: AliSayyah

piccolo/columns/column_types.py

@@ -890,18 +890,18 @@ def column_type(self):
             return "NUMERIC"
 
     @property
-    def precision(self):
+    def precision(self) -> t.Optional[int]:
         """
         The total number of digits allowed.
         """
-        return self.digits[0]
+        return self.digits[0] if self.digits is not None else None
 
     @property
-    def scale(self):
+    def scale(self) -> t.Optional[int]:
         """
         The number of digits after the decimal point.
         """
-        return self.digits[1]
+        return self.digits[1] if self.digits is not None else None
 
     def __init__(
         self,

tests/utils/test_pydantic.py

@@ -45,6 +45,20 @@ class Movie(Table):
 
         pydantic_model(box_office=decimal.Decimal("1.0"))
 
+    def test_numeric_without_digits(self):
+        class Movie(Table):
+            box_office = Numeric()
+
+        try:
+            create_pydantic_model(table=Movie)
+        except TypeError:
+            self.fail(
+                "Creating numeric field without"
+                " digits failed in pydantic model."
+            )
+        else:
+            self.assertTrue(True)
+
 
 class TestSecretColumn(TestCase):
     def test_secret_param(self):
@@ -93,7 +107,6 @@ class TestColumnHelpText(TestCase):
     """
 
     def test_help_text_present(self):
-
         help_text = "In millions of US dollars."
 
         class Movie(Table):
@@ -115,7 +128,6 @@ class TestTableHelpText(TestCase):
     """
 
     def test_help_text_present(self):
-
         help_text = "Movies which were released in cinemas."
 
         class Movie(Table, help_text=help_text):