Merge lp:~jderose/microfiber/db.update into lp:microfiber

[Jason Gerard DeRose]

For details, see this bug:

  https://bugs.launchpad.net/microfiber/+bug/1160107

Changes:

 * Adds method Database.update(doc, func, *args)

 * Adds test for same

[David Jordan (dmj726)]

Looks good. Approved!

review: Approve

=== modified file 'microfiber/__init__.py'
--- microfiber/__init__.py	2013-03-25 17:00:26 +0000
+++ microfiber/__init__.py	2013-03-26 00:33:21 +0000
@@ -58,6 +58,7 @@
 import math
 import platform
 from collections import namedtuple
+import logging
 
 from dbase32 import RANDOM_BITS, RANDOM_BYTES, RANDOM_B32LEN
 from dbase32.rfc3548 import random_id
@@ -86,6 +87,7 @@
 )
 
 __version__ = '13.04.0'
+log = logging.getLogger()
 USER_AGENT = 'Microfiber/{} ({} {}; {})'.format(__version__, 
     platform.dist()[0], platform.dist()[1], platform.machine()
 )
@@ -1156,3 +1158,17 @@
             separators=(',', ': '),
         )
 
+    def update(self, doc, func, *args):
+        """
+        Update *doc* with *func*, then save, with one retry after a conflict.
+        """
+        func(doc, *args)
+        try:
+            self.save(doc)
+            return doc
+        except Conflict:
+            log.warning('Conflict saving %s', doc['_id'])
+        doc = self.get(doc['_id'])
+        func(doc, *args)
+        self.save(doc)
+        return doc

=== modified file 'microfiber/tests/__init__.py'
--- microfiber/tests/__init__.py	2013-03-24 21:06:04 +0000
+++ microfiber/tests/__init__.py	2013-03-26 00:33:21 +0000
@@ -1838,6 +1838,99 @@
             {'reduce': True, 'include_docs': True},
         ))
 
+    def test_update(self):
+        class DummyConflict(microfiber.Conflict):
+            def __init__(self):
+                pass
+
+        class DummyDatabase(microfiber.Database):
+            def __init__(self, doc, newrev):
+                self._calls = []
+                self._id = doc['_id']
+                self._rev = doc['_rev']
+                self._doc = deepcopy(doc)
+                self._newrev = newrev
+
+            def save(self, doc):
+                self._calls.append(('save', deepcopy(doc)))
+                if doc['_rev'] != self._rev:
+                    raise DummyConflict()
+                doc['_rev'] = self._newrev
+                return doc
+
+            def get(self, _id):
+                assert _id == self._id
+                self._calls.append(('get', _id))
+                return deepcopy(self._doc)
+
+            def _func(self, doc, key, value):
+                self._calls.append(('func', deepcopy(doc), key, value))
+                doc[key] = value
+
+        _id = random_id()
+        rev1 = random_id()
+        rev2 = random_id()
+        rev3 = random_id()
+        key = random_id()
+        value = random_id()
+        doc1 = {
+            '_id': _id,
+            '_rev': rev1,
+            'hello': 'world',
+        }
+        doc1a = {
+            '_id': _id,
+            '_rev': rev1,
+            'hello': 'world',
+            key: value,
+        }
+        doc2 = {
+            '_id': _id,
+            '_rev': rev2,
+            'stuff': 'junk',
+        }
+        doc2a = {
+            '_id': _id,
+            '_rev': rev2,
+            'stuff': 'junk',
+            key: value,
+        }
+
+        # Test when there is a mid-flight collision:
+        db = DummyDatabase(deepcopy(doc2), rev3)
+        self.assertEqual(
+            db.update(deepcopy(doc1), db._func, key, value),
+            {
+                '_id': _id,
+                '_rev': rev3,
+                'stuff': 'junk',
+                key: value,
+            }
+        )
+        self.assertEqual(db._calls, [
+            ('func', doc1, key, value),
+            ('save', doc1a),
+            ('get', _id),
+            ('func', doc2, key, value),
+            ('save', doc2a),
+        ])
+
+        # Test when there is no conflict:
+        db = DummyDatabase(deepcopy(doc1), rev3)
+        self.assertEqual(
+            db.update(deepcopy(doc1), db._func, key, value),
+            {
+                '_id': _id,
+                '_rev': rev3,
+                'hello': 'world',
+                key: value,
+            }
+        )
+        self.assertEqual(db._calls, [
+            ('func', doc1, key, value),
+            ('save', doc1a),
+        ])
+
 
 class LiveTestCase(TestCase):
     """