Trigger owners-autoassign processing for change readyForReview

The owners-autoassign plugin has historically ignored
all refs/changes/*/meta ref-updates, because they are related
to modifications on the change meta-data.

There is one moment, though, where the evaluation make a lot
of sense, and it is a meta-data only change, triggering only
the ref-update of the refs/changes/*/meta: a WIP change is
set ready for review.

Very often, the user that is working on a WIP change does not
like to have lots of reviewers and therefore tends to remove
them from the reviewers' list. Also, WIP changes do not generate
any attention-set action because the change isn't supposed to
be ready for review.

When the change is later set ready for review *without any
further updates*, the owners-autoassign must process the change
and, if there aren't already the expected owners added,
should add all the owners retrieved from the processing
of the OWNERS files as reviewers.
The detection of the diff cannot rely though on the new SHA1
of the event but rather get the latest patch-set SHA1 and
compute the diff against its change-base.

Bug: Issue 14679
Change-Id: I6b2b6f9b947615f96e331709aa257d54b9c52f07
3 files changed
tree: 7813ca371ee86f6f22e39996da76441ab935158c
  1. .settings/
  2. lib/
  3. owners/
  4. owners-autoassign/
  5. owners-common/
  6. tools/
  7. .bazelignore
  8. .bazelrc
  9. .gitignore
  10. bazlets.bzl
  11. BUILD
  14. external_plugin_deps.bzl
  15. external_plugin_deps_standalone.bzl

Gerrit OWNERS Plugin

This plugin provides some Prolog predicates that can be used to add customized validation checks based on the approval of ‘path owners’ of a particular folder in the project.

That allows creating a single big project including multiple components and users have different roles depending on the particular path where changes are being proposed. A user can be “owner” in a specific directory, and thus influencing the approvals of changes there, but cannot do the same in others paths, so assuring a kind of dynamic subproject access rights.

How it works

There are currently two main prolog public verbs:

add_owner_approval/3 (UserList, InList, OutList) appends label('Owner-Approval', need(_)) to InList building OutList if UserList has no users contained in the defined owners of this path change.

In other words, the predicate just copies InList to OutList if at least one of the elements in UserList is an owner.

add_owner_approval/2 (InList, OutList) appends label('Owner-Approval', need(_)) to InList building OutList if no owners has given a Code-Review +2 to this path change.

This predicate is similar to the first one but generates a UserList with an hardcoded policy.

Since add_owner_approval/3 is not using hard coded policies, it can be suitable for complex customizations.

Auto assigner

There is a second plugin, gerrit-owners-autoassign which depends on gerrit-owners. It will automatically assign all of the owners to review a change when it's created or updated.

How to build

This plugin is built with Bazel and two build modes are supported:

  • Standalone
  • In Gerrit tree

Build standalone

To build the plugin, issue the following command:

  bazel build :all

The output is created in


To execute the tests run:

  bazel test //...

This project can be imported into the Eclipse IDE:


Build in Gerrit tree

Create symbolic links of the owners and owners-autoassign folders and of the external_plugin_deps.bzl file to the Gerrit source code /plugins directory.

Create a symbolic link of the owners-common plugin to the Gerrit source code directory.

Then build the owners and owners-autoassign plugins with the usual Gerrit plugin compile command.


   $ git clone
   $ git clone
   $ cd gerrit/plugins
   $ ln -s ../../owners/owners .
   $ ln -s ../../owners/owners-autoassign .
   $ ln -sf ../../owners/external_plugin_deps.bzl .
   $ cd ..
   $ ln -s ../owners/owners-common .
   $ bazel build plugins/owners plugins/owners-autoassign

NOTE: the owners-common folder is producing shared artifacts for the two plugins and does not need to be built separately being a direct dependency of the build process. Its resulting .jar must not be installed in gerrit plugins directory.

The output is created in


To execute the tests run:

  bazel test owners-common:test

This project can be imported into the Eclipse IDE:

Add the plugin name to the CUSTOM_PLUGINS in Gerrit core in tools/bzl/plugins.bzl file and run: