fix: invalidate favicon cache when clearing watch history (#4286)

Co-authored-by: snowyukitty <270071858+snowyukitty@users.noreply.github.com>

changedetectionio/model/Watch.py

@@ -45,7 +45,7 @@ BROTLI_COMPRESS_SIZE_THRESHOLD = int(os.getenv('SNAPSHOT_BROTLI_COMPRESSION_THRE
 
 # Module-level favicon filename cache: data_dir → basename (or None)
 # Keyed by data_dir so it survives Watch object recreation, deepcopy, and concurrent requests.
-# Invalidated explicitly in bump_favicon() when a new favicon is saved.
+# Invalidated explicitly when the favicon is saved or the watch history is cleared.
 _FAVICON_FILENAME_CACHE: dict = {}
 
 minimum_seconds_recheck_time = int(os.getenv('MINIMUM_SECONDS_RECHECK_TIME', 3))
@@ -334,6 +334,8 @@ class model(EntityPersistenceMixin, watch_base):
                 continue
             os.unlink(item)
 
+        _FAVICON_FILENAME_CACHE.pop(self.data_dir, None)
+
         # Force the attr to recalculate
         bump = self.history
 
@@ -896,7 +898,7 @@ class model(EntityPersistenceMixin, watch_base):
 
         Uses a module-level cache keyed by data_dir to survive Watch object recreation,
         deepcopy (which drops instance attrs), and concurrent request races.
-        Invalidated by bump_favicon() when a new favicon is saved.
+        Invalidated when a favicon is saved or the watch history is cleared.
 
         Returns:
             str: Basename of the favicon file, or None if not found.

changedetectionio/tests/unit/test_watch_model.py

@@ -6,6 +6,7 @@
 import unittest
 import os
 import pickle
+import tempfile
 from copy import deepcopy
 
 from changedetectionio.model import Watch, Tag
@@ -249,6 +250,35 @@ class TestDiffBuilder(unittest.TestCase):
         self.assertLess(elapsed, 0.5,
                        f"Deepcopy too slow ({elapsed:.3f}s for 10 copies) - might be copying datastore")
 
+
+class TestFaviconFilenameCache(unittest.TestCase):
+
+    def test_clear_watch_invalidates_cached_favicon_filename(self):
+        from changedetectionio.model.Watch import _FAVICON_FILENAME_CACHE
+
+        mock_datastore = {'settings': {'application': {}}, 'watching': {}}
+
+        with tempfile.TemporaryDirectory() as datastore_path:
+            watch = Watch.model(
+                datastore_path=datastore_path,
+                __datastore=mock_datastore,
+                default={'url': 'https://example.com'}
+            )
+            watch.ensure_data_dir_exists()
+            self.addCleanup(_FAVICON_FILENAME_CACHE.pop, watch.data_dir, None)
+
+            favicon_path = os.path.join(watch.data_dir, 'favicon.ico')
+            with open(favicon_path, 'wb') as favicon_file:
+                favicon_file.write(b'favicon')
+
+            self.assertEqual(watch.get_favicon_filename(), 'favicon.ico')
+
+            watch.clear_watch()
+
+            self.assertFalse(os.path.exists(favicon_path))
+            self.assertIsNone(watch.get_favicon_filename())
+
+
 class TestLLMDiffSummaryCache(unittest.TestCase):
     """Tests for get_llm_diff_summary / save_llm_diff_summary — version-pair + prompt-hash caching."""