delete(): improved multiple-id code and tests

Received all feedback as of PR#151 comment:

  <#151 (comment)>

In particular, better idiomatic python code for the multiple id cases, and
an improved test that will delete all documents except one, rather than deleting
all in one go.

Author: Cosimo Streppone

pysolr.py

@@ -825,15 +825,12 @@ def delete(self, id=None, q=None, commit=True, waitFlush=None, waitSearcher=None
         elif id is not None and q is not None:
             raise ValueError('You many only specify "id" OR "q", not both.')
         elif id is not None:
-            if type(id) not in (list, set):
-                id = [ id ]
+            if not isinstance(id, (list, set, tuple)):
+                id = [id]
             else:
-                id = filter(lambda x: x is not None, id)
-            if len(id) > 0:
-                m = '<delete>'
-                for i in id:
-                    m += '<id>%s</id>' % i
-                m += '</delete>'
+                id = filter(None, id)
+            if id:
+                m = '<delete>%s</delete>' % ''.join('<id>%s</id>' % i for i in id)
             else:
                 raise ValueError('The list of documents to delete was empty.')
         elif q is not None:

tests/client.py

@@ -2,6 +2,7 @@
 from __future__ import unicode_literals
 
 import datetime
+import random
 
 from pysolr import (Solr, Results, SolrError, unescape_html, safe_urlencode,
                     force_unicode, force_bytes, sanitize, json, ET, IS_PY3,
@@ -460,7 +461,14 @@ def test_delete(self):
         self.solr.commit()
         self.assertEqual(len(self.solr.search('*:*')), len(self.docs))
         to_delete = [doc['id'] for doc in self.docs]
+        # Extract a random document from the list, to later check it wasn't deleted
+        graced_doc_id = to_delete.pop(random.randint(0, len(to_delete) - 1))
         self.solr.delete(id=to_delete)
+        # There should be only one left, our graced id
+        self.assertEqual(len(self.solr.search('*:*')), 1)
+        self.assertEqual(len(self.solr.search('id:%s' % graced_doc_id)), 1)
+        # Now we can wipe the graced document too. None should be left.
+        self.solr.delete(id=graced_doc_id)
         self.assertEqual(len(self.solr.search('*:*')), 0)
 
         # Can't delete when the list of documents is empty