Remove assertions for redundant SerializerMethodField source args.

docs/topics/3.0-announcement.md

@@ -699,18 +699,6 @@ The argument to `SerializerMethodField` is now optional, and defaults to `get_<f
         def get_billing_details(self, account):
             return calculate_billing(account)
 
-In order to ensure a consistent code style an assertion error will be raised if you include a redundant method name argument that matches the default method name. For example, the following code *will raise an error*:
-
-    billing_details = serializers.SerializerMethodField('get_billing_details')
-
-#### Enforcing consistent `source` usage.
-
-I've see several codebases that unnecessarily include the `source` argument, setting it to the same value as the field name. This usage is redundant and confusing, making it less obvious that `source` is usually not required.
-
-The following usage will *now raise an error*:
-
-    email = serializers.EmailField(source='email')
-
 #### The `UniqueValidator` and `UniqueTogetherValidator` classes.
 
 REST framework now provides new validators that allow you to ensure field uniqueness, while still using a completely explicit `Serializer` class instead of using `ModelSerializer`.

rest_framework/fields.py

@@ -210,16 +210,6 @@ def bind(self, field_name, parent):
         Called when a field is added to the parent serializer instance.
         """
 
-        # In order to enforce a consistent style, we error if a redundant
-        # 'source' argument has been used. For example:
-        # my_field = serializer.CharField(source='my_field')
-        assert self.source != field_name, (
-            "It is redundant to specify `source='%s'` on field '%s' in "
-            "serializer '%s', because it is the same as the field name. "
-            "Remove the `source` keyword argument." %
-            (field_name, self.__class__.__name__, parent.__class__.__name__)
-        )
-
         self.field_name = field_name
         self.parent = parent
 
@@ -1219,17 +1209,7 @@ def __init__(self, method_name=None, **kwargs):
         super(SerializerMethodField, self).__init__(**kwargs)
 
     def bind(self, field_name, parent):
-        # In order to enforce a consistent style, we error if a redundant
-        # 'method_name' argument has been used. For example:
-        # my_field = serializer.CharField(source='my_field')
         default_method_name = 'get_{field_name}'.format(field_name=field_name)
-        assert self.method_name != default_method_name, (
-            "It is redundant to specify `%s` on SerializerMethodField '%s' in "
-            "serializer '%s', because it is the same as the default method name. "
-            "Remove the `method_name` argument." %
-            (self.method_name, field_name, parent.__class__.__name__)
-        )
-
         # The method name should default to `get_{field_name}`.
         if self.method_name is None:
             self.method_name = default_method_name

tests/test_fields.py

@@ -81,17 +81,6 @@ class ExampleSerializer(serializers.Serializer):
         assert serializer.is_valid()
         assert serializer.validated_data == {'other': 'abc'}
 
-    def test_redundant_source(self):
-        class ExampleSerializer(serializers.Serializer):
-            example_field = serializers.CharField(source='example_field')
-        with pytest.raises(AssertionError) as exc_info:
-            ExampleSerializer().fields
-        assert str(exc_info.value) == (
-            "It is redundant to specify `source='example_field'` on field "
-            "'CharField' in serializer 'ExampleSerializer', because it is the "
-            "same as the field name. Remove the `source` keyword argument."
-        )
-
 
 class TestReadOnly:
     def setup(self):
@@ -1078,16 +1067,3 @@ def get_example_field(self, obj):
         assert serializer.data == {
             'example_field': 'ran get_example_field(123)'
         }
-
-    def test_redundant_method_name(self):
-        class ExampleSerializer(serializers.Serializer):
-            example_field = serializers.SerializerMethodField('get_example_field')
-
-        with pytest.raises(AssertionError) as exc_info:
-            ExampleSerializer().fields
-        assert str(exc_info.value) == (
-            "It is redundant to specify `get_example_field` on "
-            "SerializerMethodField 'example_field' in serializer "
-            "'ExampleSerializer', because it is the same as the default "
-            "method name. Remove the `method_name` argument."
-        )