UI + Fetching - Be more helpful when a filter contains no text, suggest ways to deal with images in filters (#1819)

changedetectionio/update_worker.py

@@ -3,7 +3,7 @@ import threading
 import queue
 import time
 
-from changedetectionio import content_fetcher
+from changedetectionio import content_fetcher, html_tools
 from .processors.text_json_diff import FilterNotFoundInResponse
 from .processors.restock_diff import UnableToExtractRestockData
 
@@ -251,7 +251,20 @@ class update_worker(threading.Thread):
                         # Totally fine, it's by choice - just continue on, nothing more to care about
                         # Page had elements/content but no renderable text
                         # Backend (not filters) gave zero output
-                        self.datastore.update_watch(uuid=uuid, update_obj={'last_error': "Got HTML content but no text found (With {} reply code).".format(e.status_code)})
+                        extra_help = ""
+                        if e.has_filters:
+                            # Maybe it contains an image? offer a more helpful link
+                            has_img = html_tools.include_filters(include_filters='img',
+                                                                 html_content=e.html_content)
+                            if has_img:
+                                extra_help = ", it's possible that the filters you have give an empty result or contain only an image <a href=\"https://github.com/dgtlmoon/changedetection.io/wiki/Detecting-changes-in-images\">more help here</a>."
+                            else:
+                                extra_help = ", it's possible that the filters were found, but contained no usable text."
+
+                        self.datastore.update_watch(uuid=uuid, update_obj={
+                            'last_error': f"Got HTML content but no text found (With {e.status_code} reply code){extra_help}"
+                        })
+
                         if e.screenshot:
                             self.datastore.save_screenshot(watch_uuid=uuid, screenshot=e.screenshot)
                         process_changedetection_results = False