importsource: Catch importer crash when skipping; Fix original changelog entry; Add new tests (#6203)

Prevents a crash when "skip" is selected in the importer and
`task.imported_items()` runs into a condition branch that supposedly
should never be reached:

```
  File "beets/beets/importer/tasks.py", line 254, in imported_items
    assert False
           ^^^^^
AssertionError
```

- Since for items/albums that should be skipped, looping through
`task.imported_items()` is not required anyway, the fix here is to exit
early from the function that calls it.
- Additionally this PR fixes the original changelog entry which was
located at an older releases "new features list". Also now it briefly
explains to changelog readers what the plugin actually does.
- Two new tests were added that proof that "skip doesn't crash" and
reimports never "suggest removal of source files"

---------

Co-authored-by: Doron Behar <doron.behar@gmail.com>

beetsplug/importsource.py

@@ -39,6 +39,8 @@ class ImportSourcePlugin(BeetsPlugin):
         )
 
     def prevent_suggest_removal(self, session, task):
+        if task.skip:
+            return
         for item in task.imported_items():
             if "mb_albumid" in item:
                 self.stop_suggestions_for_albums.add(item.mb_albumid)

docs/changelog.rst

@@ -24,6 +24,9 @@ New features:
       to receive extra verbose logging around last.fm results and how they are
       resolved. The ``extended_debug`` config setting and ``--debug`` option
       have been removed.
+- :doc:`plugins/importsource`: Added new plugin that tracks original import
+  paths and optionally suggests removing source files when items are removed
+  from the library.
 - :doc:`plugins/mbpseudo`: Add a new `mbpseudo` plugin to proactively receive
       MusicBrainz pseudo-releases as recommendations during import.
 - Added support for Python 3.13.
@@ -491,7 +494,6 @@ New features:
   ``beet list -a title:something`` or ``beet list artpath:cover``. Consequently
   album queries involving ``path`` field have been sped up, like ``beet list -a
   path:/path/``.
-- :doc:`plugins/importsource`: Added plugin
 - :doc:`plugins/ftintitle`: New ``keep_in_artist`` option for the plugin, which
   allows keeping the "feat." part in the artist metadata while still changing
   the title.

test/plugins/test_importsource.py

@@ -18,7 +18,7 @@
 import os
 import time
 
-from beets import importer
+from beets import importer, plugins
 from beets.test.helper import AutotagImportTestCase, PluginMixin, control_stdin
 from beets.util import syspath
 from beetsplug.importsource import ImportSourcePlugin
@@ -113,3 +113,34 @@ class ImportSourceTest(PluginMixin, AutotagImportTestCase):
             assert current_mtime == original_mtime, (
                 f"Source file timestamp changed: {path}"
             )
+
+    def test_prevent_suggest_removal_on_reimport(self):
+        """Test that removal suggestions are prevented during reimport."""
+        album = self.lib.albums().get()
+        mb_albumid = album.mb_albumid
+
+        # Reimport from library
+        reimporter = self.setup_importer(import_dir=self.libdir)
+        reimporter.add_choice(importer.Action.APPLY)
+        reimporter.run()
+
+        plugin = plugins._instances[0]
+        assert mb_albumid in plugin.stop_suggestions_for_albums
+
+        # Calling suggest_removal should exit early without prompting
+        item = self.lib.items().get()
+        plugin.suggest_removal(item)
+        assert os.path.exists(item.source_path)
+
+    def test_prevent_suggest_removal_handles_skipped_task(self):
+        """Test that skipped tasks don't crash prevent_suggest_removal."""
+
+        class MockTask:
+            skip = True
+
+            def imported_items(self):
+                return "whatever"
+
+        plugin = plugins._instances[0]
+        mock_task = MockTask()
+        plugin.prevent_suggest_removal(None, mock_task)