Assert selected file exists

qutebrowser/browser/shared.py

@@ -434,5 +434,8 @@ def _execute_fileselect_command(
     if not qb_mode == FileSelectionMode.multiple_files:
         if len(selected_files) > 1:
             message.warning("More than one file/folder chosen, using only the first")
-            return selected_files[:1]
+            selected_files = selected_files[:1]
+    for selected_file in selected_files:
+        if not os.path.exists(selected_file):
+            message.warning(f"Selected non-existent file '{selected_file}'")
     return selected_files

tests/end2end/features/editor.feature

@@ -240,6 +240,16 @@ Feature: Opening external editors
         And the error "Failed to open tempfile *" should be shown
         And "Failed to delete tempfile *" should be logged with level error
 
+    ## Select non-existent file
+
+    Scenario: Select non-existent file
+        When I set fileselect.handler to external
+        When I setup a fake single_file fileselector selecting "tests/end2end/data/numbers/non-existent.txt" and writes to a temporary file
+        And I open data/fileselect.html
+        And I run :click-element id single_file
+        Then the javascript message "Files: non-existent.txt" should not be logged
+        And the warning "Selected non-existent file *tests/end2end/data/numbers/non-existent.txt'" should be shown
+
     ## Select folder
 
     @qtwebkit_skip