use None instead of empty string for missing digests and thumbs

superset-frontend/src/components/ListViewCard/index.tsx

@@ -153,7 +153,7 @@ interface CardProps {
   subtitle?: ReactNode;
   url?: string;
   linkComponent?: ComponentType<LinkProps>;
-  imgURL?: string;
+  imgURL?: string | null;
   imgFallbackURL?: string;
   imgPosition?: BackgroundPosition;
   description: string;

superset-frontend/src/dashboard/components/AddSliceCard/AddSliceCard.tsx

@@ -174,7 +174,7 @@ const AddSliceCard: FC<{
   lastModified?: string;
   sliceName: string;
   style?: CSSProperties;
-  thumbnailUrl?: string;
+  thumbnailUrl?: string | null;
   visType: string;
 }> = ({
   datasourceUrl,

superset-frontend/src/types/Dashboard.ts

@@ -24,7 +24,7 @@ export interface Dashboard {
   slug?: string | null;
   url: string;
   dashboard_title: string;
-  thumbnail_url: string;
+  thumbnail_url: string | null;
   published: boolean;
   css?: string | null;
   json_metadata?: string | null;

superset/charts/schemas.py

@@ -162,6 +162,7 @@ class ChartEntityResponseSchema(Schema):
     certification_details = fields.String(
         metadata={"description": certification_details_description}
     )
+    thumbnail_url = fields.String(allow_none=True)
 
 
 class ChartPostSchema(Schema):

superset/dashboards/schemas.py

@@ -212,7 +212,7 @@ class DashboardGetResponseSchema(Schema):
     dashboard_title = fields.String(
         metadata={"description": dashboard_title_description}
     )
-    thumbnail_url = fields.String()
+    thumbnail_url = fields.String(allow_none=True)
     published = fields.Boolean()
     css = fields.String(metadata={"description": css_description})
     json_metadata = fields.String(metadata={"description": json_metadata_description})

superset/models/dashboard.py

@@ -225,19 +225,19 @@ def dashboard_link(self) -> Markup:
         return Markup(f'<a href="{self.url}">{title}</a>')
 
     @property
-    def digest(self) -> str:
+    def digest(self) -> str | None:
         return get_dashboard_digest(self)
 
     @property
-    def thumbnail_url(self) -> str:
+    def thumbnail_url(self) -> str | None:
         """
         Returns a thumbnail URL with a HEX digest. We want to avoid browser cache
         if the dashboard has changed
         """
         if digest := self.digest:
             return f"/api/v1/dashboard/{self.id}/thumbnail/{digest}/"
 
-        return ""
+        return None
 
     @property
     def changed_by_name(self) -> str:

superset/models/slice.py

@@ -247,19 +247,19 @@ def data(self) -> dict[str, Any]:
         }
 
     @property
-    def digest(self) -> str:
+    def digest(self) -> str | None:
         return get_chart_digest(self)
 
     @property
-    def thumbnail_url(self) -> str:
+    def thumbnail_url(self) -> str | None:
         """
         Returns a thumbnail URL with a HEX digest. We want to avoid browser cache
         if the dashboard has changed
         """
         if digest := self.digest:
             return f"/api/v1/chart/{self.id}/thumbnail/{digest}/"
 
-        return ""
+        return None
 
     @property
     def json_data(self) -> str:

superset/thumbnails/digest.py

@@ -90,17 +90,16 @@ def _adjust_string_with_rls(
     return unique_string
 
 
-def get_dashboard_digest(dashboard: Dashboard) -> str:
+def get_dashboard_digest(dashboard: Dashboard) -> str | None:
     config = current_app.config
-    datasources = dashboard.datasources
     try:
         executor_type, executor = get_executor(
             executors=config["THUMBNAIL_EXECUTORS"],
             model=dashboard,
             current_user=get_current_user(),
         )
     except ExecutorNotFoundError:
-        return ""
+        return None
 
     if func := config["THUMBNAIL_DASHBOARD_DIGEST_FUNC"]:
         return func(dashboard, executor_type, executor)
@@ -111,28 +110,29 @@ def get_dashboard_digest(dashboard: Dashboard) -> str:
     )
 
     unique_string = _adjust_string_for_executor(unique_string, executor_type, executor)
-    unique_string = _adjust_string_with_rls(unique_string, datasources, executor)
+    unique_string = _adjust_string_with_rls(
+        unique_string, dashboard.datasources, executor
+    )
 
     return md5_sha_from_str(unique_string)
 
 
-def get_chart_digest(chart: Slice) -> str:
+def get_chart_digest(chart: Slice) -> str | None:
     config = current_app.config
-    datasource = chart.datasource
     try:
         executor_type, executor = get_executor(
             executors=config["THUMBNAIL_EXECUTORS"],
             model=chart,
             current_user=get_current_user(),
         )
     except ExecutorNotFoundError:
-        return ""
+        return None
 
     if func := config["THUMBNAIL_CHART_DIGEST_FUNC"]:
         return func(chart, executor_type, executor)
 
     unique_string = f"{chart.params or ''}.{executor}"
     unique_string = _adjust_string_for_executor(unique_string, executor_type, executor)
-    unique_string = _adjust_string_with_rls(unique_string, [datasource], executor)
+    unique_string = _adjust_string_with_rls(unique_string, [chart.datasource], executor)
 
     return md5_sha_from_str(unique_string)

superset/utils/screenshots.py

@@ -56,15 +56,18 @@
 
 class BaseScreenshot:
     driver_type = current_app.config["WEBDRIVER_TYPE"]
+    url: str
+    digest: str | None
+    screenshot: bytes | None
     thumbnail_type: str = ""
     element: str = ""
     window_size: WindowSize = DEFAULT_SCREENSHOT_WINDOW_SIZE
     thumb_size: WindowSize = DEFAULT_SCREENSHOT_THUMBNAIL_SIZE
 
-    def __init__(self, url: str, digest: str):
-        self.digest: str = digest
+    def __init__(self, url: str, digest: str | None):
+        self.digest = digest
         self.url = url
-        self.screenshot: bytes | None = None
+        self.screenshot = None
 
     def driver(self, window_size: WindowSize | None = None) -> WebDriver:
         window_size = window_size or self.window_size
@@ -227,7 +230,7 @@ class ChartScreenshot(BaseScreenshot):
     def __init__(
         self,
         url: str,
-        digest: str,
+        digest: str | None,
         window_size: WindowSize | None = None,
         thumb_size: WindowSize | None = None,
     ):
@@ -248,7 +251,7 @@ class DashboardScreenshot(BaseScreenshot):
     def __init__(
         self,
         url: str,
-        digest: str,
+        digest: str | None,
         window_size: WindowSize | None = None,
         thumb_size: WindowSize | None = None,
     ):

tests/unit_tests/thumbnails/test_digest.py

@@ -214,7 +214,7 @@ def prepare_datasource_mock(
             False,
             False,
             [],
-            "",
+            None,
         ),
         (
             None,
@@ -353,7 +353,7 @@ def test_dashboard_digest(
             False,
             False,
             None,
-            "",
+            None,
         ),
         (
             None,