From build process perspective there are three types of plugins:

  • Maven driven

  • Bazel tree driven

  • Bazel standalone

These types can be combined: if both files in plugin’s root directory exist:

  • BUILD

  • pom.xml

the plugin can be built with both Bazel and Maven.

Maven driven build

If plugin contains pom.xml file, it can be built with Maven as usually:

mvn clean package

Exceptions from the rule above:

Exception 1:

Plugin’s pom.xml references snapshot version of plugin API: 2.8-SNAPSHOT. In this case there are two possibilities:

  • switch to release API. Change plugin API version in pom.xml from 2.8-SNAPSHOT to 2.8.1 and repeat step 1 above.

  • build and install SNAPSHOT version of plugin API in local Maven repository:

./tools/maven/api.sh install

Exception 2:

Plugin’s pom.xml references other own or foreign (unpublished) libraries or even other Gerrit plugins. These libraries and/or plugins must be built and installed in local Maven repository. Clone the related projects and issue

mvn install

Repeat step 1. above.

Bazel in tree driven

The fact that plugin contains BUILD file doesn’t mean that building this plugin from the plugin directory works.

Bazel in tree driven means it can only be built from within Gerrit tree. Clone or link the plugin into gerrit/plugins directory:

cd gerrit
bazel build plugins/<plugin-name>:<plugin-name>

The output can be normally found in the following directory:

bazel-bin/plugins/<plugin-name>/<plugin-name>.jar

Some plugins describe their build process in src/main/resources/Documentation/build.md file. It may worth checking.

Error Prone checks

Error Prone checks are enabled by default for core Gerrit and all core plugins. To enable the checks for custom plugins, add it in the error_prone_packages group in tools/BUILD.

Plugins with external dependencies

If the plugin has external dependencies, then they must be included from Gerrit’s own WORKSPACE file. This can be achieved by including them in external_plugin_deps.bzl. During the build in Gerrit tree, this file must be copied over the dummy one in plugins directory.

Example for content of external_plugin_deps.bzl file:

load("//tools/bzl:maven_jar.bzl", "maven_jar")

def external_plugin_deps():
  maven_jar(
      name = 'org_apache_tika_tika_core',
      artifact = 'org.apache.tika:tika-core:1.12',
      sha1 = '5ab95580d22fe1dee79cffbcd98bb509a32da09b',
  )

Bundle custom plugin in release.war

To bundle custom plugin(s) in the release.war artifact, add them to the CUSTOM_PLUGINS list in tools/bzl/plugins.bzl.

Example of tools/bzl/plugins.bzl with custom plugin my-plugin:

CORE_PLUGINS = [
    "commit-message-length-validator",
    "download-commands",
    "hooks",
    "replication",
    "reviewnotes",
    "singleusergroup",
]

CUSTOM_PLUGINS = [
    "my-plugin",
]

CUSTOM_PLUGINS_TEST_DEPS = [
    # Add custom core plugins with tests deps here
]

If the plugin(s) being bundled in the release have external dependencies, include them in plugins/external_plugin_deps. Create symbolic link from plugin’s own external_plugin_deps() file in plugins directory and prefix the file with plugin name, e.g.:

  $ cd plugins
  $ ln -s oauth/external_plugin_deps.bzl oauth_external_plugin_deps.bzl
  $ ln -s uploadvalidator/external_plugin_deps.bzl uploadvalidator_external_plugin_deps.bzl

Now the plugin specific dependency files can be imported:

load(":oauth_external_plugin_deps.bzl", oauth_deps="external_plugin_deps")
load(":uploadvalidator_external_plugin_deps.bzl", uploadvalidator_deps="external_plugin_deps")

def external_plugin_deps():
  oauth_deps()
  uploadvalidator_deps()
Note
 Since tools/bzl/plugins.bzl and plugins/external_plugin_deps.bzl are part of Gerrit’s source code and the version of the war is based on the state of the git repository that is built; you should commit this change before building, otherwise the version will be marked as 'dirty'.

Bazel standalone driven

Only few plugins support that mode for now:

cd reviewers
bazel build reviewers

Part of Gerrit Code Review