Fixed #28795 -- Removed 'not in' checks and used dict.setdefault().

13 files changed, 27 insertions, 60 deletions

diff --git a/django/contrib/gis/apps.py b/django/contrib/gis/apps.py
index ffbbe63273..662ae43d8d 100644
--- a/django/contrib/gis/apps.py
+++ b/django/contrib/gis/apps.py
@@ -8,5 +8,4 @@ class GISConfig(AppConfig):
     verbose_name = _("GIS")
 
     def ready(self):
-        if 'geojson' not in serializers.BUILTIN_SERIALIZERS:
-            serializers.BUILTIN_SERIALIZERS['geojson'] = "django.contrib.gis.serializers.geojson"
+        serializers.BUILTIN_SERIALIZERS.setdefault('geojson', 'django.contrib.gis.serializers.geojson')
diff --git a/django/contrib/gis/db/models/fields.py b/django/contrib/gis/db/models/fields.py
index f0329b2ec1..fea3cfc260 100644
--- a/django/contrib/gis/db/models/fields.py
+++ b/django/contrib/gis/db/models/fields.py
@@ -255,9 +255,8 @@ class GeometryField(BaseSpatialField):
                     'srid': self.srid,
                     }
         defaults.update(kwargs)
-        if (self.dim > 2 and 'widget' not in kwargs and
-                not getattr(defaults['form_class'].widget, 'supports_3d', False)):
-            defaults['widget'] = forms.Textarea
+        if self.dim > 2 and not getattr(defaults['form_class'].widget, 'supports_3d', False):
+            defaults.setdefault('widget', forms.Textarea)
         return super().formfield(**defaults)
 
     def select_format(self, compiler, sql, params):
diff --git a/django/contrib/gis/gdal/raster/source.py b/django/contrib/gis/gdal/raster/source.py
index bf84eeef1a..8c35b45cb5 100644
--- a/django/contrib/gis/gdal/raster/source.py
+++ b/django/contrib/gis/gdal/raster/source.py
@@ -381,27 +381,14 @@ class GDALRaster(GDALRasterBase):
         consult the GDAL_RESAMPLE_ALGORITHMS constant.
         """
         # Get the parameters defining the geotransform, srid, and size of the raster
-        if 'width' not in ds_input:
-            ds_input['width'] = self.width
-
-        if 'height' not in ds_input:
-            ds_input['height'] = self.height
-
-        if 'srid' not in ds_input:
-            ds_input['srid'] = self.srs.srid
-
-        if 'origin' not in ds_input:
-            ds_input['origin'] = self.origin
-
-        if 'scale' not in ds_input:
-            ds_input['scale'] = self.scale
-
-        if 'skew' not in ds_input:
-            ds_input['skew'] = self.skew
-
+        ds_input.setdefault('width', self.width)
+        ds_input.setdefault('height', self.height)
+        ds_input.setdefault('srid', self.srs.srid)
+        ds_input.setdefault('origin', self.origin)
+        ds_input.setdefault('scale', self.scale)
+        ds_input.setdefault('skew', self.skew)
         # Get the driver, name, and datatype of the target raster
-        if 'driver' not in ds_input:
-            ds_input['driver'] = self.driver.name
+        ds_input.setdefault('driver', self.driver.name)
 
         if 'name' not in ds_input:
             ds_input['name'] = self.name + '_copy.' + self.driver.name
diff --git a/django/db/migrations/operations/models.py b/django/db/migrations/operations/models.py
index 9754181e84..a1ff594602 100644
--- a/django/db/migrations/operations/models.py
+++ b/django/db/migrations/operations/models.py
@@ -693,8 +693,8 @@ class AlterModelOptions(ModelOptionOperation):
         model_state.options = dict(model_state.options)
         model_state.options.update(self.options)
         for key in self.ALTER_OPTION_KEYS:
-            if key not in self.options and key in model_state.options:
-                del model_state.options[key]
+            if key not in self.options:
+                model_state.options.pop(key, False)
         state.reload_model(app_label, self.name_lower, delay=True)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 57da2fe68b..e7456de037 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -692,8 +692,7 @@ class Query:
             # in the parent list. Again, it must be mentioned to ensure that
             # only "must include" fields are pulled in.
             for model in orig_opts.get_parent_list():
-                if model not in seen:
-                    seen[model] = set()
+                seen.setdefault(model, set())
             for model, values in seen.items():
                 callback(target, model, values)
 
diff --git a/django/forms/boundfield.py b/django/forms/boundfield.py
index 6acae1c59b..dba54e588a 100644
--- a/django/forms/boundfield.py
+++ b/django/forms/boundfield.py
@@ -87,20 +87,10 @@ class BoundField:
 
         attrs = attrs or {}
         attrs = self.build_widget_attrs(attrs, widget)
-        auto_id = self.auto_id
-        if auto_id and 'id' not in attrs and 'id' not in widget.attrs:
-            if not only_initial:
-                attrs['id'] = auto_id
-            else:
-                attrs['id'] = self.html_initial_id
-
-        if not only_initial:
-            name = self.html_name
-        else:
-            name = self.html_initial_name
-
+        if self.auto_id and 'id' not in widget.attrs:
+            attrs.setdefault('id', self.html_initial_id if only_initial else self.auto_id)
         return widget.render(
-            name=name,
+            name=self.html_initial_name if only_initial else self.html_name,
             value=self.value(),
             attrs=attrs,
             renderer=self.form.renderer,
diff --git a/django/http/response.py b/django/http/response.py
index ae14333053..c07dc5b6e0 100644
--- a/django/http/response.py
+++ b/django/http/response.py
@@ -136,10 +136,7 @@ class HttpResponseBase:
         self._headers[header.lower()] = (header, value)
 
     def __delitem__(self, header):
-        try:
-            del self._headers[header.lower()]
-        except KeyError:
-            pass
+        self._headers.pop(header.lower(), False)
 
     def __getitem__(self, header):
         return self._headers[header.lower()][1]
diff --git a/django/middleware/locale.py b/django/middleware/locale.py
index ee057786ee..2399debf6e 100644
--- a/django/middleware/locale.py
+++ b/django/middleware/locale.py
@@ -57,6 +57,5 @@ class LocaleMiddleware(MiddlewareMixin):
 
         if not (i18n_patterns_used and language_from_path):
             patch_vary_headers(response, ('Accept-Language',))
-        if 'Content-Language' not in response:
-            response['Content-Language'] = language
+        response.setdefault('Content-Language', language)
         return response
diff --git a/django/middleware/security.py b/django/middleware/security.py
index 7bcb72738e..296567432f 100644
--- a/django/middleware/security.py
+++ b/django/middleware/security.py
@@ -37,10 +37,10 @@ class SecurityMiddleware(MiddlewareMixin):
                 sts_header = sts_header + "; preload"
             response["strict-transport-security"] = sts_header
 
-        if self.content_type_nosniff and 'x-content-type-options' not in response:
-            response["x-content-type-options"] = "nosniff"
+        if self.content_type_nosniff:
+            response.setdefault('x-content-type-options', 'nosniff')
 
-        if self.xss_filter and 'x-xss-protection' not in response:
-            response["x-xss-protection"] = "1; mode=block"
+        if self.xss_filter:
+            response.setdefault('x-xss-protection', '1; mode=block')
 
         return response
diff --git a/django/template/defaulttags.py b/django/template/defaulttags.py
index 212aa8987a..143082c47d 100644
--- a/django/template/defaulttags.py
+++ b/django/template/defaulttags.py
@@ -225,8 +225,7 @@ class IfChangedNode(Node):
     def render(self, context):
         # Init state storage
         state_frame = self._get_context_stack_frame(context)
-        if self not in state_frame:
-            state_frame[self] = None
+        state_frame.setdefault(self)
 
         nodelist_true_output = None
         if self._varlist:
diff --git a/django/views/decorators/http.py b/django/views/decorators/http.py
index 81355d7725..1c8502fb1e 100644
--- a/django/views/decorators/http.py
+++ b/django/views/decorators/http.py
@@ -103,8 +103,8 @@ def condition(etag_func=None, last_modified_func=None):
             if request.method in ('GET', 'HEAD'):
                 if res_last_modified and not response.has_header('Last-Modified'):
                     response['Last-Modified'] = http_date(res_last_modified)
-                if res_etag and not response.has_header('ETag'):
-                    response['ETag'] = res_etag
+                if res_etag:
+                    response.setdefault('ETag', res_etag)
 
             return response
 
diff --git a/django/views/generic/base.py b/django/views/generic/base.py
index 7938aeaebc..cea077c6d1 100644
--- a/django/views/generic/base.py
+++ b/django/views/generic/base.py
@@ -21,8 +21,7 @@ class ContextMixin:
     extra_context = None
 
     def get_context_data(self, **kwargs):
-        if 'view' not in kwargs:
-            kwargs['view'] = self
+        kwargs.setdefault('view', self)
         if self.extra_context is not None:
             kwargs.update(self.extra_context)
         return kwargs
diff --git a/tests/runtests.py b/tests/runtests.py
index 57b8a45404..ae2d693ac2 100755
--- a/tests/runtests.py
+++ b/tests/runtests.py
@@ -455,8 +455,7 @@ if __name__ == "__main__":
     if options.settings:
         os.environ['DJANGO_SETTINGS_MODULE'] = options.settings
     else:
-        if "DJANGO_SETTINGS_MODULE" not in os.environ:
-            os.environ['DJANGO_SETTINGS_MODULE'] = 'test_sqlite'
+        os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'test_sqlite')
         options.settings = os.environ['DJANGO_SETTINGS_MODULE']
 
     if options.selenium: