Merge lp:~jml/launchpad/more-services into lp:launchpad

[Jonathan Lange]

Move Twisted fault support and the base LaunchpadFault to lp.services. Move 'synchronize' helper to lp.services.

This branch extracts some drive-by-cleanups from my uber-branch lp:~jml/launchpad/ssh-key-auth.

Specifically:
  1. The higher-order function "synchronize" is moved to lp.services
  2. The "trap_fault" helper for XMLRPC Twisted code is moved to lp.services.twistedsupport
  3. The "LaunchpadFault" base class for all of our XMLRPC faults is moved to lp.services.xmlrpc
  4. A XXX comment from 2005 is deleted

I know it's a bit of a grab-bag of changes, but they are all conceptually quite simple, so I hope it's an easy enough branch to review.

[Abel Deuring (adeuring)]

review: Approve (code)

=== modified file 'lib/canonical/launchpad/scripts/__init__.py'
--- lib/canonical/launchpad/scripts/__init__.py	2010-03-18 21:30:51 +0000
+++ lib/canonical/launchpad/scripts/__init__.py	2010-04-10 13:58:26 +0000
@@ -46,9 +46,6 @@
 # We should probably split out all the stuff in this directory that
 # doesn't rely on Zope and migrate it to canonical/scripts.
 
-# XXX SteveAlexander 2005-04-11:
-# This is a total mess.  I need to work out what this all means.
-
 class NullItem:
     def __init__(self, context, handler, info, *argdata):
         newcontext = GroupingContextDecorator(context)

=== modified file 'lib/canonical/launchpad/xmlrpc/faults.py'
--- lib/canonical/launchpad/xmlrpc/faults.py	2010-03-14 20:15:34 +0000
+++ lib/canonical/launchpad/xmlrpc/faults.py	2010-04-10 13:58:26 +0000
@@ -15,7 +15,6 @@
     'BranchNameInUse',
     'BranchUniqueNameConflict',
     'CannotHaveLinkedBranch',
-    'check_fault',
     'FileBugGotProductAndDistro',
     'FileBugMissingProductOrDistribution',
     'InvalidBranchIdentifier',
@@ -42,41 +41,8 @@
     ]
 
 
-import xmlrpclib
-
-
 from lp.registry.interfaces.projectgroup import IProjectGroup
-
-
-def check_fault(fault, *fault_classes):
-    """Check if 'fault's faultCode matches any of 'fault_classes'.
-
-    :param fault: An instance of `xmlrpclib.Fault`.
-    :param fault_classes: Any number of `LaunchpadFault` subclasses.
-    """
-    for cls in fault_classes:
-        if fault.faultCode == cls.error_code:
-            return True
-    return False
-
-
-class LaunchpadFault(xmlrpclib.Fault):
-    """Base class for a Launchpad XMLRPC fault.
-
-    Subclasses should define a unique error_code and a msg_template,
-    which will be interpolated with the given keyword arguments.
-    """
-
-    error_code = None
-    msg_template = None
-
-    def __init__(self, **kw):
-        assert self.error_code is not None, (
-            "Subclasses must define error_code.")
-        assert self.msg_template is not None, (
-            "Subclasses must define msg_template.")
-        msg = self.msg_template % kw
-        xmlrpclib.Fault.__init__(self, self.error_code, msg)
+from lp.services.xmlrpc import LaunchpadFault
 
 
 class NoSuchProduct(LaunchpadFault):

=== modified file 'lib/canonical/launchpad/xmlrpc/tests/test_authserver.py'
--- lib/canonical/launchpad/xmlrpc/tests/test_authserver.py	2009-06-25 05:30:52 +0000
+++ lib/canonical/launchpad/xmlrpc/tests/test_authserver.py	2010-04-10 13:58:26 +0000
@@ -16,6 +16,7 @@
 from canonical.launchpad.xmlrpc.authserver import AuthServerAPIView
 from canonical.testing.layers import DatabaseFunctionalLayer
 
+
 class GetUserAndSSHKeysTests(TestCaseWithFactory):
     """Tests for the implementation of `IAuthServer.getUserAndSSHKeys`.
     """
@@ -28,17 +29,10 @@
         self.authserver = AuthServerAPIView(
             private_root.authserver, TestRequest())
 
-    def assertFaultEqual(self, expected_fault, observed_fault):
-        """Assert that `expected_fault` equals `observed_fault`."""
-        self.assertIsInstance(observed_fault, faults.LaunchpadFault)
-        self.assertEqual(expected_fault.faultCode, observed_fault.faultCode)
-        self.assertEqual(
-            expected_fault.faultString, observed_fault.faultString)
-
     def test_user_not_found(self):
         # getUserAndSSHKeys returns the NoSuchPersonWithName fault if there is
         # no Person of the given name.
-        self.assertFaultEqual(
+        self.assertEqual(
             faults.NoSuchPersonWithName('no-one'),
             self.authserver.getUserAndSSHKeys('no-one'))
 

=== removed file 'lib/canonical/launchpad/xmlrpc/tests/test_faults.py'
--- lib/canonical/launchpad/xmlrpc/tests/test_faults.py	2009-06-25 05:30:52 +0000
+++ lib/canonical/launchpad/xmlrpc/tests/test_faults.py	1970-01-01 00:00:00 +0000
@@ -1,65 +0,0 @@
-# Copyright 2009 Canonical Ltd.  This software is licensed under the
-# GNU Affero General Public License version 3 (see the file LICENSE).
-
-"""Tests for `canonical.launchpad.xmlrpc.faults`."""
-
-__metaclass__ = type
-
-import unittest
-
-from lp.testing import TestCase
-from canonical.launchpad.xmlrpc import faults
-
-
-class TestFaultOne(faults.LaunchpadFault):
-    """An arbitrary subclass of `LaunchpadFault`.
-
-    This class and `TestFaultTwo` are a pair of distinct `LaunchpadFault`
-    subclasses to use in tests.
-    """
-
-    error_code = 1001
-    msg_template = "Fault one."
-
-
-class TestFaultTwo(faults.LaunchpadFault):
-    """Another arbitrary subclass of `LaunchpadFault`.
-
-    This class and `TestFaultOne` are a pair of distinct `LaunchpadFault`
-    subclasses to use in tests.
-    """
-
-    error_code = 1002
-    msg_template = "Fault two."
-
-
-class TestTrapFault(TestCase):
-    """Tests for `check_fault`."""
-
-    def test_wrong_fault(self):
-        # check_fault returns False if the passed fault does not have the code
-        # of one of the passed classes.
-        self.assertFalse(
-            faults.check_fault(TestFaultOne(), TestFaultTwo))
-
-    def test_no_fault_classes(self):
-        # check_fault returns False if there are no passed classes.
-        self.assertFalse(
-            faults.check_fault(TestFaultOne()))
-
-    def test_matches(self):
-        # check_fault returns True if the passed fault has the code of the
-        # passed class.
-        self.assertTrue(
-            faults.check_fault(TestFaultOne(), TestFaultOne))
-
-    def test_matches_one_of_set(self):
-        # check_fault returns True if the passed fault has the code of one of
-        # the passed classes.
-        self.assertTrue(faults.check_fault(
-            TestFaultOne(), TestFaultOne, TestFaultTwo))
-
-
-def test_suite():
-    return unittest.TestLoader().loadTestsFromName(__name__)
-

=== modified file 'lib/lp/code/xmlrpc/tests/test_branch.py'
--- lib/lp/code/xmlrpc/tests/test_branch.py	2010-02-22 06:16:47 +0000
+++ lib/lp/code/xmlrpc/tests/test_branch.py	2010-04-10 13:58:26 +0000
@@ -21,6 +21,7 @@
 from lp.testing import TestCaseWithFactory
 from lazr.uri import URI
 from lp.code.xmlrpc.branch import PublicCodehostingAPI
+from lp.services.xmlrpc import LaunchpadFault
 from canonical.launchpad.xmlrpc import faults
 from canonical.testing import DatabaseFunctionalLayer
 
@@ -62,7 +63,7 @@
         """Assert that `lp_url_path` path expands to `unique_name`."""
         results = self.api.resolve_lp_path(lp_url_path)
         # This improves the error message if results happens to be a fault.
-        if isinstance(results, faults.LaunchpadFault):
+        if isinstance(results, LaunchpadFault):
             raise results
         for url in results['urls']:
             self.assertEqual('/' + unique_name, URI(url).path)

=== modified file 'lib/lp/code/xmlrpc/tests/test_codehosting.py'
--- lib/lp/code/xmlrpc/tests/test_codehosting.py	2010-02-24 19:01:25 +0000
+++ lib/lp/code/xmlrpc/tests/test_codehosting.py	2010-04-10 13:58:26 +0000
@@ -137,13 +137,6 @@
         self.branch_lookup = frontend.getBranchLookup()
         self.getLastActivity = frontend.getLastActivity
 
-    def assertFaultEqual(self, expected_fault, observed_fault):
-        """Assert that `expected_fault` equals `observed_fault`."""
-        self.assertIsInstance(observed_fault, faults.LaunchpadFault)
-        self.assertEqual(expected_fault.faultCode, observed_fault.faultCode)
-        self.assertEqual(
-            expected_fault.faultString, observed_fault.faultString)
-
     def assertMirrorFailed(self, branch, failure_message, num_failures=1):
         """Assert that `branch` failed to mirror.
 
@@ -204,7 +197,7 @@
         # exist.
         invalid_id = self.getUnusedBranchID()
         fault = self.storage.startMirroring(invalid_id)
-        self.assertFaultEqual(faults.NoBranchWithID(invalid_id), fault)
+        self.assertEqual(faults.NoBranchWithID(invalid_id), fault)
 
     def test_mirrorFailed(self):
         branch = self.factory.makeAnyBranch()
@@ -220,7 +213,7 @@
         branch_id = self.getUnusedBranchID()
         failure_message = self.factory.getUniqueString()
         fault = self.storage.mirrorFailed(branch_id, failure_message)
-        self.assertFaultEqual(faults.NoBranchWithID(branch_id), fault)
+        self.assertEqual(faults.NoBranchWithID(branch_id), fault)
 
     def test_mirrorComplete(self):
         # mirrorComplete marks the branch as having been successfully
@@ -240,7 +233,7 @@
         branch_id = self.getUnusedBranchID()
         fault = self.storage.mirrorComplete(
             branch_id, self.factory.getUniqueString())
-        self.assertFaultEqual(faults.NoBranchWithID(branch_id), fault)
+        self.assertEqual(faults.NoBranchWithID(branch_id), fault)
 
     def test_mirrorComplete_resets_failure_count(self):
         # mirrorComplete marks the branch as successfully mirrored and removes
@@ -388,7 +381,7 @@
         stacked_branch = self.factory.makeAnyBranch()
         url = self.factory.getUniqueURL()
         fault = self.storage.setStackedOn(stacked_branch.id, url)
-        self.assertFaultEqual(faults.NoSuchBranch(url), fault)
+        self.assertEqual(faults.NoSuchBranch(url), fault)
 
     def test_setStackedOnNoBranchWithID(self):
         # If setStackedOn is called for a branch that doesn't exist, it will
@@ -397,7 +390,7 @@
             branch_type=BranchType.MIRRORED)
         branch_id = self.getUnusedBranchID()
         fault = self.storage.setStackedOn(branch_id, stacked_on_branch.url)
-        self.assertFaultEqual(faults.NoBranchWithID(branch_id), fault)
+        self.assertEqual(faults.NoBranchWithID(branch_id), fault)
 
 
 class AcquireBranchToPullTestsViaEndpoint(TestCaseWithFactory,
@@ -499,13 +492,6 @@
         self.factory = frontend.getLaunchpadObjectFactory()
         self.branch_lookup = frontend.getBranchLookup()
 
-    def assertFaultEqual(self, expected_fault, observed_fault):
-        """Assert that `expected_fault` equals `observed_fault`."""
-        self.assertIsInstance(observed_fault, faults.LaunchpadFault)
-        self.assertEqual(expected_fault.faultCode, observed_fault.faultCode)
-        self.assertEqual(
-            expected_fault.faultString, observed_fault.faultString)
-
     def test_createBranch(self):
         # createBranch creates a branch with the supplied details and the
         # caller as registrant.
@@ -527,7 +513,7 @@
         path = escape(u'invalid')
         fault = self.branchfs.createBranch(requester.id, path)
         login(ANONYMOUS)
-        self.assertFaultEqual(faults.InvalidPath(path), fault)
+        self.assertEqual(faults.InvalidPath(path), fault)
 
     def test_createBranch_junk(self):
         # createBranch can create +junk branches.
@@ -565,7 +551,7 @@
         message = "Project 'no-such-product' does not exist."
         fault = self.branchfs.createBranch(
             owner.id, escape('/~%s/no-such-product/%s' % (owner.name, name)))
-        self.assertFaultEqual(faults.NotFound(message), fault)
+        self.assertEqual(faults.NotFound(message), fault)
 
     def test_createBranch_other_user(self):
         # Creating a branch under another user's directory fails.
@@ -578,7 +564,7 @@
         fault = self.branchfs.createBranch(
             creator.id,
             escape('/~%s/%s/%s' % (other_person.name, product.name, name)))
-        self.assertFaultEqual(faults.PermissionDenied(message), fault)
+        self.assertEqual(faults.PermissionDenied(message), fault)
 
     def test_createBranch_bad_name(self):
         # Creating a branch with an invalid name fails.
@@ -590,7 +576,7 @@
         fault = self.branchfs.createBranch(
             owner.id, escape(
                 '/~%s/%s/%s' % (owner.name, product.name, invalid_name)))
-        self.assertFaultEqual(faults.PermissionDenied(message), fault)
+        self.assertEqual(faults.PermissionDenied(message), fault)
 
     def test_createBranch_unicode_name(self):
         # Creating a branch with an invalid name fails.
@@ -603,7 +589,7 @@
         fault = self.branchfs.createBranch(
             owner.id, escape(
                 '/~%s/%s/%s' % (owner.name, product.name, invalid_name)))
-        self.assertFaultEqual(
+        self.assertEqual(
             faults.PermissionDenied(message), fault)
 
     def test_createBranch_bad_user(self):
@@ -614,7 +600,7 @@
         message = "User/team 'no-one' does not exist."
         fault = self.branchfs.createBranch(
             owner.id, escape('/~no-one/%s/%s' % (product.name, name)))
-        self.assertFaultEqual(faults.NotFound(message), fault)
+        self.assertEqual(faults.NotFound(message), fault)
 
     def test_createBranch_bad_user_bad_product(self):
         # If both the user and the product are not found, then the missing
@@ -625,7 +611,7 @@
         message = "User/team 'no-one' does not exist."
         fault = self.branchfs.createBranch(
             owner.id, escape('/~no-one/no-product/%s' % (name,)))
-        self.assertFaultEqual(faults.NotFound(message), fault)
+        self.assertEqual(faults.NotFound(message), fault)
 
     def test_createBranch_not_branch(self):
         # Trying to create a branch at a path that's not valid for branches
@@ -634,7 +620,7 @@
         path = escape('/~%s' % owner.name)
         fault = self.branchfs.createBranch(owner.id, path)
         message = "Cannot create branch at '%s'" % path
-        self.assertFaultEqual(faults.PermissionDenied(message), fault)
+        self.assertEqual(faults.PermissionDenied(message), fault)
 
     def test_createBranch_source_package(self):
         # createBranch can take the path to a source package branch and create
@@ -671,7 +657,7 @@
             branch_name)
         fault = self.branchfs.createBranch(owner.id, escape(unique_name))
         message = "No such distribution: 'ningnangnong'."
-        self.assertFaultEqual(faults.NotFound(message), fault)
+        self.assertEqual(faults.NotFound(message), fault)
 
     def test_createBranch_invalid_distroseries(self):
         # If createBranch is called with the path to a non-existent
@@ -685,7 +671,7 @@
             branch_name)
         fault = self.branchfs.createBranch(owner.id, escape(unique_name))
         message = "No such distribution series: 'ningnangnong'."
-        self.assertFaultEqual(faults.NotFound(message), fault)
+        self.assertEqual(faults.NotFound(message), fault)
 
     def test_createBranch_invalid_sourcepackagename(self):
         # If createBranch is called with the path to an invalid source
@@ -698,7 +684,7 @@
             branch_name)
         fault = self.branchfs.createBranch(owner.id, escape(unique_name))
         message = "No such source package: 'ningnangnong'."
-        self.assertFaultEqual(faults.NotFound(message), fault)
+        self.assertEqual(faults.NotFound(message), fault)
 
     def test_initialMirrorRequest(self):
         # The default 'next_mirror_time' for a newly created hosted branch
@@ -727,21 +713,21 @@
     def assertCannotTranslate(self, requester, path):
         """Assert that we cannot translate 'path'."""
         fault = self.branchfs.translatePath(requester.id, path)
-        self.assertFaultEqual(faults.PathTranslationError(path), fault)
+        self.assertEqual(faults.PathTranslationError(path), fault)
 
     def assertNotFound(self, requester, path):
         """Assert that the given path cannot be found."""
         if requester not in [LAUNCHPAD_ANONYMOUS, LAUNCHPAD_SERVICES]:
             requester = requester.id
         fault = self.branchfs.translatePath(requester, path)
-        self.assertFaultEqual(faults.PathTranslationError(path), fault)
+        self.assertEqual(faults.PathTranslationError(path), fault)
 
     def assertPermissionDenied(self, requester, path):
         """Assert that looking at the given path gives permission denied."""
         if requester not in [LAUNCHPAD_ANONYMOUS, LAUNCHPAD_SERVICES]:
             requester = requester.id
         fault = self.branchfs.translatePath(requester, path)
-        self.assertFaultEqual(faults.PermissionDenied(), fault)
+        self.assertEqual(faults.PermissionDenied(), fault)
 
     def _makeProductWithDevFocus(self, private=False):
         """Make a stacking-enabled product with a development focus.
@@ -769,7 +755,7 @@
         requester = self.factory.makePerson()
         path = escape(u'invalid')
         fault = self.branchfs.translatePath(requester.id, path)
-        self.assertFaultEqual(faults.InvalidPath(path), fault)
+        self.assertEqual(faults.InvalidPath(path), fault)
 
     def test_translatePath_branch(self):
         requester = self.factory.makePerson()

=== modified file 'lib/lp/codehosting/sshserver/accesslog.py'
--- lib/lp/codehosting/sshserver/accesslog.py	2010-03-19 10:43:51 +0000
+++ lib/lp/codehosting/sshserver/accesslog.py	2010-04-10 13:58:26 +0000
@@ -29,24 +29,10 @@
 
 from canonical.config import config
 from canonical.launchpad.scripts import WatchedFileHandler
+from lp.services.utils import synchronize
 from lp.services.twistedsupport.loggingsupport import set_up_oops_reporting
 
 
-def synchronize(source, target, add, remove):
-    """Update 'source' to match 'target' using 'add' and 'remove'.
-
-    Changes the container 'source' so that it equals 'target', calling 'add'
-    with any object in 'target' not in 'source' and 'remove' with any object
-    not in 'target' but in 'source'.
-    """
-    need_to_add = [obj for obj in target if obj not in source]
-    need_to_remove = [obj for obj in source if obj not in target]
-    for obj in need_to_add:
-        add(obj)
-    for obj in need_to_remove:
-        remove(obj)
-
-
 class LoggingManager:
     """Class for managing codehosting logging."""
 

=== modified file 'lib/lp/codehosting/sshserver/auth.py'
--- lib/lp/codehosting/sshserver/auth.py	2009-06-25 04:06:00 +0000
+++ lib/lp/codehosting/sshserver/auth.py	2010-04-10 13:58:26 +0000
@@ -42,7 +42,7 @@
 from lp.codehosting.sshserver import accesslog
 from lp.codehosting.sshserver.session import (
     launch_smart_server, PatchedSSHSession)
-from lp.codehosting.vfs.branchfsclient import trap_fault
+from lp.services.twistedsupport.xmlrpc import trap_fault
 from canonical.config import config
 from canonical.launchpad.xmlrpc import faults
 

=== modified file 'lib/lp/codehosting/vfs/branchfs.py'
--- lib/lp/codehosting/vfs/branchfs.py	2010-03-23 03:35:13 +0000
+++ lib/lp/codehosting/vfs/branchfs.py	2010-04-10 13:58:26 +0000
@@ -83,16 +83,17 @@
 from zope.interface import implements, Interface
 
 from lp.codehosting.vfs.branchfsclient import (
-    BlockingProxy, BranchFileSystemClient, trap_fault)
+    BlockingProxy, BranchFileSystemClient)
 from lp.codehosting.vfs.transport import (
     AsyncVirtualServer, AsyncVirtualTransport, _MultiServer,
     get_chrooted_transport, get_readonly_transport, TranslationError)
 from canonical.config import config
+from canonical.launchpad.xmlrpc import faults
 from lp.code.enums import BranchType
 from lp.code.interfaces.branchlookup import IBranchLookup
 from lp.code.interfaces.codehosting import (
     BRANCH_TRANSPORT, CONTROL_TRANSPORT, LAUNCHPAD_SERVICES)
-from canonical.launchpad.xmlrpc import faults
+from lp.services.twistedsupport.xmlrpc import trap_fault
 
 
 class BadUrl(Exception):

=== modified file 'lib/lp/codehosting/vfs/branchfsclient.py'
--- lib/lp/codehosting/vfs/branchfsclient.py	2010-03-23 02:34:35 +0000
+++ lib/lp/codehosting/vfs/branchfsclient.py	2010-04-10 13:58:26 +0000
@@ -11,13 +11,11 @@
     'BlockingProxy',
     'BranchFileSystemClient',
     'NotInCache',
-    'trap_fault',
     ]
 
 import time
 
 from twisted.internet import defer
-from twisted.web.xmlrpc import Fault
 
 from lp.code.interfaces.codehosting import BRANCH_TRANSPORT
 
@@ -136,19 +134,3 @@
                 'translatePath', self._user_id, path)
             deferred.addCallback(self._addToCache, path)
             return deferred
-
-
-def trap_fault(failure, *fault_classes):
-    """Trap a fault, based on fault code.
-
-    :param failure: A Twisted L{Failure}.
-    :param *fault_codes: `LaunchpadFault` subclasses.
-    :raise Failure: if 'failure' is not a Fault failure, or if the fault code
-        does not match the given codes.
-    :return: The Fault if it matches one of the codes.
-    """
-    failure.trap(Fault)
-    fault = failure.value
-    if fault.faultCode in [cls.error_code for cls in fault_classes]:
-        return fault
-    raise failure

=== modified file 'lib/lp/codehosting/vfs/tests/test_branchfsclient.py'
--- lib/lp/codehosting/vfs/tests/test_branchfsclient.py	2010-03-23 02:34:35 +0000
+++ lib/lp/codehosting/vfs/tests/test_branchfsclient.py	2010-04-10 13:58:26 +0000
@@ -9,16 +9,13 @@
 
 import unittest
 
-from twisted.python.failure import Failure
 from twisted.trial.unittest import TestCase
 
 from lp.codehosting.vfs.branchfsclient import (
-    BranchFileSystemClient, NotInCache, trap_fault)
+    BranchFileSystemClient, NotInCache)
 from lp.codehosting.inmemory import InMemoryFrontend, XMLRPCWrapper
 from lp.code.interfaces.codehosting import BRANCH_TRANSPORT
 from lp.testing import FakeTime
-from canonical.launchpad.xmlrpc.tests.test_faults import (
-    TestFaultOne, TestFaultTwo)
 
 
 class TestBranchFileSystemClient(TestCase):
@@ -250,56 +247,6 @@
             [branch1.unique_name, branch2.unique_name], seen_branches)
 
 
-class TestTrapFault(TestCase):
-    """Tests for `trap_fault`."""
-
-    def makeFailure(self, exception_factory, *args, **kwargs):
-        """Make a `Failure` from the given exception factory."""
-        try:
-            raise exception_factory(*args, **kwargs)
-        except:
-            return Failure()
-
-    def assertRaisesFailure(self, failure, function, *args, **kwargs):
-        try:
-            function(*args, **kwargs)
-        except Failure, raised_failure:
-            self.assertEqual(failure, raised_failure)
-
-    def test_raises_non_faults(self):
-        # trap_fault re-raises any failures it gets that aren't faults.
-        failure = self.makeFailure(RuntimeError, 'example failure')
-        self.assertRaisesFailure(failure, trap_fault, failure, TestFaultOne)
-
-    def test_raises_faults_with_wrong_code(self):
-        # trap_fault re-raises any failures it gets that are faults but have
-        # the wrong fault code.
-        failure = self.makeFailure(TestFaultOne)
-        self.assertRaisesFailure(failure, trap_fault, failure, TestFaultTwo)
-
-    def test_raises_faults_if_no_codes_given(self):
-        # If trap_fault is not given any fault codes, it re-raises the fault
-        # failure.
-        failure = self.makeFailure(TestFaultOne)
-        self.assertRaisesFailure(failure, trap_fault, failure)
-
-    def test_returns_fault_if_code_matches(self):
-        # trap_fault returns the Fault inside the Failure if the fault code
-        # matches what's given.
-        failure = self.makeFailure(TestFaultOne)
-        fault = trap_fault(failure, TestFaultOne)
-        self.assertEqual(TestFaultOne.error_code, fault.faultCode)
-        self.assertEqual(TestFaultOne.msg_template, fault.faultString)
-
-    def test_returns_fault_if_code_matches_one_of_set(self):
-        # trap_fault returns the Fault inside the Failure if the fault code
-        # matches even one of the given fault codes.
-        failure = self.makeFailure(TestFaultOne)
-        fault = trap_fault(failure, TestFaultOne, TestFaultTwo)
-        self.assertEqual(TestFaultOne.error_code, fault.faultCode)
-        self.assertEqual(TestFaultOne.msg_template, fault.faultString)
-
-
 def test_suite():
     return unittest.TestLoader().loadTestsFromName(__name__)
 

=== added file 'lib/lp/services/twistedsupport/tests/test_xmlrpc.py'
--- lib/lp/services/twistedsupport/tests/test_xmlrpc.py	1970-01-01 00:00:00 +0000
+++ lib/lp/services/twistedsupport/tests/test_xmlrpc.py	2010-04-10 13:58:26 +0000
@@ -0,0 +1,90 @@
+# Copyright 2010 Canonical Ltd.  This software is licensed under the
+# GNU Affero General Public License version 3 (see the file LICENSE).
+
+"""Tests for Twisted XML-RPC support."""
+
+__metaclass__ = type
+
+import unittest
+
+from twisted.python.failure import Failure
+from twisted.trial.unittest import TestCase
+
+from lp.services.xmlrpc import LaunchpadFault
+from lp.services.twistedsupport.xmlrpc import trap_fault
+
+
+class TestFaultOne(LaunchpadFault):
+    """An arbitrary subclass of `LaunchpadFault`.
+
+    This class and `TestFaultTwo` are a pair of distinct `LaunchpadFault`
+    subclasses to use in tests.
+    """
+
+    error_code = 1001
+    msg_template = "Fault one."
+
+
+class TestFaultTwo(LaunchpadFault):
+    """Another arbitrary subclass of `LaunchpadFault`.
+
+    This class and `TestFaultOne` are a pair of distinct `LaunchpadFault`
+    subclasses to use in tests.
+    """
+
+    error_code = 1002
+    msg_template = "Fault two."
+
+
+class TestTrapFault(TestCase):
+    """Tests for `trap_fault`."""
+
+    def makeFailure(self, exception_factory, *args, **kwargs):
+        """Make a `Failure` from the given exception factory."""
+        try:
+            raise exception_factory(*args, **kwargs)
+        except:
+            return Failure()
+
+    def assertRaisesFailure(self, failure, function, *args, **kwargs):
+        try:
+            function(*args, **kwargs)
+        except Failure, raised_failure:
+            self.assertEqual(failure, raised_failure)
+
+    def test_raises_non_faults(self):
+        # trap_fault re-raises any failures it gets that aren't faults.
+        failure = self.makeFailure(RuntimeError, 'example failure')
+        self.assertRaisesFailure(failure, trap_fault, failure, TestFaultOne)
+
+    def test_raises_faults_with_wrong_code(self):
+        # trap_fault re-raises any failures it gets that are faults but have
+        # the wrong fault code.
+        failure = self.makeFailure(TestFaultOne)
+        self.assertRaisesFailure(failure, trap_fault, failure, TestFaultTwo)
+
+    def test_raises_faults_if_no_codes_given(self):
+        # If trap_fault is not given any fault codes, it re-raises the fault
+        # failure.
+        failure = self.makeFailure(TestFaultOne)
+        self.assertRaisesFailure(failure, trap_fault, failure)
+
+    def test_returns_fault_if_code_matches(self):
+        # trap_fault returns the Fault inside the Failure if the fault code
+        # matches what's given.
+        failure = self.makeFailure(TestFaultOne)
+        fault = trap_fault(failure, TestFaultOne)
+        self.assertEqual(TestFaultOne.error_code, fault.faultCode)
+        self.assertEqual(TestFaultOne.msg_template, fault.faultString)
+
+    def test_returns_fault_if_code_matches_one_of_set(self):
+        # trap_fault returns the Fault inside the Failure if the fault code
+        # matches even one of the given fault codes.
+        failure = self.makeFailure(TestFaultOne)
+        fault = trap_fault(failure, TestFaultOne, TestFaultTwo)
+        self.assertEqual(TestFaultOne.error_code, fault.faultCode)
+        self.assertEqual(TestFaultOne.msg_template, fault.faultString)
+
+
+def test_suite():
+    return unittest.TestLoader().loadTestsFromName(__name__)

=== added file 'lib/lp/services/twistedsupport/xmlrpc.py'
--- lib/lp/services/twistedsupport/xmlrpc.py	1970-01-01 00:00:00 +0000
+++ lib/lp/services/twistedsupport/xmlrpc.py	2010-04-10 13:58:26 +0000
@@ -0,0 +1,27 @@
+# Copyright 2010 Canonical Ltd.  This software is licensed under the
+# GNU Affero General Public License version 3 (see the file LICENSE).
+
+"""Support for XML-RPC stuff with Twisted."""
+
+__metaclass__ = type
+__all__ = [
+    'trap_fault',
+    ]
+
+from twisted.web.xmlrpc import Fault
+
+
+def trap_fault(failure, *fault_classes):
+    """Trap a fault, based on fault code.
+
+    :param failure: A Twisted L{Failure}.
+    :param *fault_codes: `LaunchpadFault` subclasses.
+    :raise Failure: if 'failure' is not a Fault failure, or if the fault code
+        does not match the given codes.
+    :return: The Fault if it matches one of the codes.
+    """
+    failure.trap(Fault)
+    fault = failure.value
+    if fault.faultCode in [cls.error_code for cls in fault_classes]:
+        return fault
+    raise failure

=== modified file 'lib/lp/services/utils.py'
--- lib/lp/services/utils.py	2010-03-18 22:53:50 +0000
+++ lib/lp/services/utils.py	2010-04-10 13:58:26 +0000
@@ -1,12 +1,16 @@
 # Copyright 2009 Canonical Ltd.  This software is licensed under the
 # GNU Affero General Public License version 3 (see the file LICENSE).
 
+"""Generic Python utilities.
 
-"""Implementations of the XML-RPC APIs for codehosting."""
+Functions, lists and so forth. Nothing here that does system calls or network
+stuff.
+"""
 
 __metaclass__ = type
 __all__ = [
     'iter_split',
+    'synchronize',
     'text_delta',
     'value_string',
     ]
@@ -35,6 +39,21 @@
         yield splitter.join(tokens[:i]), splitter.join(tokens[i:])
 
 
+def synchronize(source, target, add, remove):
+    """Update 'source' to match 'target' using 'add' and 'remove'.
+
+    Changes the container 'source' so that it equals 'target', calling 'add'
+    with any object in 'target' not in 'source' and 'remove' with any object
+    not in 'target' but in 'source'.
+    """
+    need_to_add = [obj for obj in target if obj not in source]
+    need_to_remove = [obj for obj in source if obj not in target]
+    for obj in need_to_add:
+        add(obj)
+    for obj in need_to_remove:
+        remove(obj)
+
+
 def value_string(item):
     """Return a unicode string representing value.
 

=== added file 'lib/lp/services/xmlrpc.py'
--- lib/lp/services/xmlrpc.py	1970-01-01 00:00:00 +0000
+++ lib/lp/services/xmlrpc.py	2010-04-10 13:58:26 +0000
@@ -0,0 +1,40 @@
+# Copyright 2010 Canonical Ltd.  This software is licensed under the
+# GNU Affero General Public License version 3 (see the file LICENSE).
+
+"""Generic code for XML-RPC in Launchpad."""
+
+__metaclass__ = type
+__all__ = [
+    'LaunchpadFault',
+    ]
+
+import xmlrpclib
+
+
+class LaunchpadFault(xmlrpclib.Fault):
+    """Base class for a Launchpad XMLRPC fault.
+
+    Subclasses should define a unique error_code and a msg_template,
+    which will be interpolated with the given keyword arguments.
+    """
+
+    error_code = None
+    msg_template = None
+
+    def __init__(self, **kw):
+        assert self.error_code is not None, (
+            "Subclasses must define error_code.")
+        assert self.msg_template is not None, (
+            "Subclasses must define msg_template.")
+        msg = self.msg_template % kw
+        xmlrpclib.Fault.__init__(self, self.error_code, msg)
+
+    def __eq__(self, other):
+        if not isinstance(other, LaunchpadFault):
+            return False
+        return (
+            self.faultCode == other.faultCode
+            and self.faultString == other.faultString)
+
+    def __ne__(self, other):
+        return not (self == other)