Implementation details: https://docs.flutter.dev/testing/errors
A new page.on_error event handler has been added. It could be used to detect such errors like failed image downloads and other "unhandled" exceptions.
import flet
from flet import Image, Page, Row
def main(page: Page):
img = Image(
src=f"/icons1/icon-512.png" # image has an invalid URL
)
page.on_error = lambda e: print("Page error:", e.data)
page.add(img)
flet.app(target=main)