Improve seq helper

CHANGELOG.md

@@ -10,6 +10,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 ### Changed
+- Validate `increment_by` parameter of `seq` helper when `value` is an instance of `datetime` [PR #247](https://github.com/model-bakers/model_bakery/pull/247)
+- [dev] Fix some `seq` tests.
 
 ### Removed
 

model_bakery/utils.py

@@ -10,6 +10,8 @@
 
 from .timezone import tz_aware
 
+__all__ = ["import_from_str", "get_calling_module", "seq"]
+
 
 def import_from_str(import_string: Optional[Union[Callable, str]]) -> Any:
     """Import an object defined as import if it is an string.
@@ -69,11 +71,9 @@ def seq(value, increment_by=1, start=None, suffix=None):
     Returns:
         object: generated values for sequential data
     """
-    if type(value) in [datetime.datetime, datetime.date, datetime.time]:
-        if start:
-            msg = "start parameter is ignored when using seq with date, time or datetime objects"
-            warnings.warn(msg)
+    _validate_sequence_parameters(value, increment_by, start, suffix)
 
+    if type(value) in [datetime.datetime, datetime.date, datetime.time]:
         if type(value) is datetime.date:
             date = datetime.datetime.combine(value, datetime.datetime.now().time())
         elif type(value) is datetime.time:
@@ -93,15 +93,29 @@ def seq(value, increment_by=1, start=None, suffix=None):
             else:
                 yield series_date
     else:
-        if suffix and not isinstance(suffix, str):
-            raise TypeError("Sequences suffix can only be a string")
-
         for n in itertools.count(start or increment_by, increment_by):
-            if suffix and not isinstance(value, str):
-                raise TypeError(
-                    "Sequences with suffix can only be used with text values"
-                )
-            elif suffix:
+            if suffix:
                 yield value + str(n) + suffix
             else:
                 yield value + type(value)(n)
+
+
+def _validate_sequence_parameters(value, increment_by, start, suffix) -> None:
+    if suffix:
+        if not isinstance(suffix, str):
+            raise TypeError("Sequences suffix can only be a string")
+
+        if not isinstance(value, str):
+            raise TypeError("Sequences with suffix can only be used with text values")
+
+    if type(value) in [datetime.datetime, datetime.date, datetime.time]:
+        if not isinstance(increment_by, datetime.timedelta):
+            raise TypeError(
+                "Sequences with values datetime.datetime, datetime.date and datetime.time, "
+                "incremente_by must be a datetime.timedelta."
+            )
+
+        if start:
+            warnings.warn(
+                "start parameter is ignored when using seq with date, time or datetime objects"
+            )

tests/test_utils.py

@@ -76,11 +76,10 @@ def test_string_suffix_and_start(self):
         assert next(sequence) == "cookie113@example.com"
 
     def test_string_invalid_suffix(self):
-        sequence = seq("cookie", suffix=42)
-
         with pytest.raises(TypeError) as exc:
-            next(sequence)
-            assert str(exc.value) == "Sequences suffix can only be a string"
+            next(seq("cookie", suffix=42))
+
+        assert str(exc.value) == "Sequences suffix can only be a string"
 
     def test_int(self):
         sequence = seq(1)
@@ -119,13 +118,12 @@ def test_float_increment_by(self):
         assert next(sequence) == pytest.approx(6.63)
 
     def test_numbers_with_suffix(self):
-        sequence = seq(1, suffix="iamnotanumber")
         with pytest.raises(TypeError) as exc:
-            next(sequence)
-            assert (
-                str(exc.value)
-                == "Sequences with suffix can only be used with text values"
-            )
+            next(seq(1, suffix="iamnotanumber"))
+
+        assert (
+            str(exc.value) == "Sequences with suffix can only be used with text values"
+        )
 
     def test_date(self):
         sequence = seq(
@@ -162,3 +160,20 @@ def test_datetime(self, settings, use_tz):
         assert next(sequence) == datetime.datetime(
             2021, 2, 12, 00, 39, 58, 457698
         ).replace(tzinfo=tzinfo)
+
+    @pytest.mark.parametrize(
+        "value",
+        [
+            datetime.datetime(2021, 2, 11, 15, 39, 58, 457698),
+            datetime.date(2021, 2, 11),
+            datetime.time(15, 39, 58, 457698),
+        ],
+    )
+    def test_should_raise_exception_for_datetime_instances(self, value):
+        with pytest.raises(TypeError) as exc:
+            next(seq(value))
+
+        assert str(exc.value) == (
+            "Sequences with values datetime.datetime, datetime.date and datetime.time, "
+            "incremente_by must be a datetime.timedelta."
+        )