Option to control if pages with no renderable content are a change (example: JS webapps that dont render any text sometimes) (#608)

changedetectionio/content_fetcher.py

@@ -3,17 +3,22 @@ import chardet
 import os
 import requests
 import time
-import urllib3.exceptions
 import sys
 
-
 class EmptyReply(Exception):
     def __init__(self, status_code, url):
         # Set this so we can use it in other parts of the app
         self.status_code = status_code
         self.url = url
         return
+    pass
 
+class ReplyWithContentButNoText(Exception):
+    def __init__(self, status_code, url):
+        # Set this so we can use it in other parts of the app
+        self.status_code = status_code
+        self.url = url
+        return
     pass
 
 

changedetectionio/fetch_site_status.py

@@ -184,6 +184,11 @@ class perform_site_check():
         # Re #340 - return the content before the 'ignore text' was applied
         text_content_before_ignored_filter = stripped_text_from_html.encode('utf-8')
 
+        # Treat pages with no renderable text content as a change? No by default
+        empty_pages_are_a_change = self.datastore.data['settings']['application'].get('empty_pages_are_a_change', False)
+        if not is_json and not empty_pages_are_a_change and len(stripped_text_from_html.strip()) == 0:
+            raise content_fetcher.ReplyWithContentButNoText(url=url, status_code=200)
+
         # We rely on the actual text in the html output.. many sites have random script vars etc,
         # in the future we'll implement other mechanisms.
 

changedetectionio/forms.py

@@ -371,6 +371,7 @@ class globalSettingsApplicationForm(commonSettingsForm):
     ignore_whitespace = BooleanField('Ignore whitespace')
     real_browser_save_screenshot = BooleanField('Save last screenshot when using Chrome?')
     removepassword_button = SubmitField('Remove password', render_kw={"class": "pure-button pure-button-primary"})
+    empty_pages_are_a_change =  BooleanField('Treat empty pages as a change?', default=False)
     render_anchor_tag_content = BooleanField('Render anchor tag content', default=False)
     fetch_backend = RadioField('Fetch Method', default="html_requests", choices=content_fetcher.available_fetchers(), validators=[ValidateContentFetcherIsReady()])
     password = SaltyPasswordField()

changedetectionio/model/App.py

@@ -30,6 +30,7 @@ class model(dict):
                     'password': False,
                     'base_url' : None,
                     'extract_title_as_title': False,
+                    'empty_pages_are_a_change': False,
                     'fetch_backend': os.getenv("DEFAULT_FETCH_BACKEND", "html_requests"),
                     'global_ignore_text': [], # List of text to ignore when calculating the comparison checksum
                     'global_subtractive_selectors': [],

changedetectionio/templates/settings.html

@@ -61,6 +61,11 @@
                         {{ render_checkbox_field(form.application.form.real_browser_save_screenshot) }}
                         <span class="pure-form-message-inline">When using a Chrome browser, a screenshot from the last check will be available on the Diff page</span>
                     </div>
+
+                    <div class="pure-control-group">
+                        {{ render_checkbox_field(form.application.form.empty_pages_are_a_change) }}
+                        <span class="pure-form-message-inline">When a page contains HTML, but no renderable text appears (empty page), is this considered a change?</span>
+                    </div>
                 {% if form.requests.proxy %}
                     <div class="pure-control-group inline-radio">
                         {{ render_field(form.requests.form.proxy, class="fetch-backend-proxy") }}

changedetectionio/tests/test_nonrenderable_pages.py

@@ -0,0 +1,102 @@
+#!/usr/bin/python3
+
+import time
+from flask import url_for
+from urllib.request import urlopen
+from .util import set_original_response, set_modified_response, live_server_setup
+
+sleep_time_for_fetch_thread = 3
+
+
+def set_nonrenderable_response():
+    test_return_data = """<html>
+    <head><title>modified head title</title></head>
+    <!-- like when some angular app was broken and doesnt render or whatever -->
+    <body>
+     </body>
+     </html>
+    """
+
+    with open("test-datastore/endpoint-content.txt", "w") as f:
+        f.write(test_return_data)
+
+    return None
+
+def test_check_basic_change_detection_functionality(client, live_server):
+    set_original_response()
+    live_server_setup(live_server)
+
+    # Add our URL to the import page
+    res = client.post(
+        url_for("import_page"),
+        data={"urls": url_for('test_endpoint', _external=True)},
+        follow_redirects=True
+    )
+
+    assert b"1 Imported" in res.data
+
+    time.sleep(sleep_time_for_fetch_thread)
+
+    # Do this a few times.. ensures we dont accidently set the status
+    for n in range(3):
+        client.get(url_for("api_watch_checknow"), follow_redirects=True)
+
+        # Give the thread time to pick it up
+        time.sleep(sleep_time_for_fetch_thread)
+
+        # It should report nothing found (no new 'unviewed' class)
+        res = client.get(url_for("index"))
+        assert b'unviewed' not in res.data
+
+
+    #####################
+    client.post(
+        url_for("settings_page"),
+        data={"application-empty_pages_are_a_change": "",
+              "requests-time_between_check-minutes": 180,
+              'application-fetch_backend': "html_requests"},
+        follow_redirects=True
+    )
+
+    # this should not trigger a change, because no good text could be converted from the HTML
+    set_nonrenderable_response()
+
+    client.get(url_for("api_watch_checknow"), follow_redirects=True)
+
+    # Give the thread time to pick it up
+    time.sleep(sleep_time_for_fetch_thread)
+
+    # It should report nothing found (no new 'unviewed' class)
+    res = client.get(url_for("index"))
+    assert b'unviewed' not in res.data
+
+
+    # ok now do the opposite
+
+    client.post(
+        url_for("settings_page"),
+        data={"application-empty_pages_are_a_change": "y",
+              "requests-time_between_check-minutes": 180,
+              'application-fetch_backend': "html_requests"},
+        follow_redirects=True
+    )
+    set_modified_response()
+
+
+    client.get(url_for("api_watch_checknow"), follow_redirects=True)
+
+    # Give the thread time to pick it up
+    time.sleep(sleep_time_for_fetch_thread)
+
+    # It should report nothing found (no new 'unviewed' class)
+    res = client.get(url_for("index"))
+    assert b'unviewed' in res.data
+
+
+
+
+    #
+    # Cleanup everything
+    res = client.get(url_for("api_delete", uuid="all"), follow_redirects=True)
+    assert b'Deleted' in res.data
+

changedetectionio/update_worker.py

@@ -52,6 +52,10 @@ class update_worker(threading.Thread):
                             raise Exception("Error - returned data from the fetch handler SHOULD be bytes")
                     except PermissionError as e:
                         self.app.logger.error("File permission error updating", uuid, str(e))
+                    except content_fetcher.ReplyWithContentButNoText as e:
+                        # Totally fine, it's by choice - just continue on, nothing more to care about
+                        # Page had elements/content but no renderable text
+                        pass
                     except content_fetcher.EmptyReply as e:
                         # Some kind of custom to-str handler in the exception handler that does this?
                         err_text = "EmptyReply: Status Code {}".format(e.status_code)