Add an option to force the load of shelf plugins

Closes gsi-upm/senpy#34

docs/plugins.rst

@@ -183,7 +183,11 @@ Training a classifier can be time time consuming. To avoid running the training
               def deactivate(self):
                   self.close()
 
-You can speficy a 'shelf_file' in your .senpy file. By default the ShelfMixin creates a file based on the plugin name and stores it in that plugin's folder.
+You can specify a 'shelf_file' in your .senpy file. By default the ShelfMixin creates a file based on the plugin name and stores it in that plugin's folder.
+
+Shelves may get corrupted if the plugin exists unexpectedly.
+A corrupt shelf prevents the plugin from loading.
+If you do not care about the pickle, you can force your plugin to remove the corrupted file and load anyway, set the  'force_shelf' to True in your .senpy file.
 
 I want to implement my service as a plugin, How i can do it?
 ????????????????????????????????????????????????????????????

senpy/models.py

@@ -237,6 +237,9 @@ class BaseModel(SenpyMixin, dict):
         self.__setitem__(self._get_key(key), value)
 
     def __delattr__(self, key):
+        try:
+            object.__delattr__(self, key)
+        except AttributeError:
             self.__delitem__(self._get_key(key))
 
     def _plain_dict(self):

senpy/plugins/__init__.py

@@ -98,8 +98,10 @@ class ShelfMixin(object):
             if os.path.isfile(self.shelf_file):
                 try:
                     self.__dict__['_sh'] = pickle.load(open(self.shelf_file, 'rb'))
-                except EOFError:
-                    logger.warning('corrupted shelf file!')
+                except (EOFError, pickle.UnpicklingError):
+                    logger.warning('{} has a corrupted shelf file!'.format(self.id))
+                    if not self.get('force_shelf', False):
+                        raise
         return self._sh
 
     @sh.deleter

tests/test_plugins.py

@@ -83,7 +83,40 @@ class PluginsTest(TestCase):
         res2 = a.analyse(input=1)
         assert res2.entries[0].nif__isString == 2
 
-    def test_two(self):
+    def test_corrupt_shelf(self):
+        ''' Reusing the values of a previous shelf '''
+
+        emptyfile = os.path.join(self.shelf_dir, "emptyfile")
+        invalidfile = os.path.join(self.shelf_dir, "invalid_file")
+        with open(emptyfile, 'w+b'), open(invalidfile, 'w+b') as inf:
+            inf.write(b'ohno')
+
+        files = {emptyfile: ['empty file', EOFError],
+                 invalidfile: ['invalid file', pickle.UnpicklingError]}
+
+        for fn in files:
+            with open(fn, 'rb') as f:
+                msg, error = files[fn]
+                a = ShelfDummyPlugin(info={
+                    'name': 'shelve',
+                    'version': 'test',
+                    'shelf_file': f.name
+                })
+                assert os.path.isfile(a.shelf_file)
+                print('Shelf file: %s' % a.shelf_file)
+                with self.assertRaises(error):
+                    # By default, raise an error
+                    a.sh['a'] = 'fromA'
+                    a.save()
+                del a._sh
+                assert os.path.isfile(a.shelf_file)
+                a.force_shelf = True
+                a.sh['a'] = 'fromA'
+                a.save()
+                b = pickle.load(f)
+                assert b['a'] == 'fromA'
+
+    def test_reuse_shelf(self):
         ''' Reusing the values of a previous shelf '''
         a = ShelfDummyPlugin(info={
             'name': 'shelve',