Default to png file type for screenshots if type is not provided and path does not include extension.

Author: Kyle McGonagle

playwright/_impl/_element_handle.py

@@ -457,7 +457,7 @@ def convert_select_option_values(
 
 def determine_screenshot_type(path: Union[str, Path]) -> Literal["jpeg", "png"]:
     mime_type, _ = mimetypes.guess_type(path)
-    if mime_type == "image/png":
+    if mime_type == "image/png" or mime_type is None:
         return "png"
     if mime_type == "image/jpeg":
         return "jpeg"

tests/async/test_screenshot.py

@@ -68,6 +68,10 @@ async def test_should_infer_screenshot_type_from_path(
     await page.screenshot(path=output_jpg_file)
     assert_image_file_format(output_jpg_file, "JPEG")
 
+    output_png_file = tmp_path / "foo"
+    await page.screenshot(path=output_png_file)
+    assert_image_file_format(output_png_file, "PNG")
+    
 
 async def test_should_screenshot_with_type_argument(page: Page, tmp_path: Path) -> None:
     output_jpeg_with_png_extension = tmp_path / "foo_jpeg.png"