= Gerrit Code Review - Building with Buck


== Installation

There is currently no binary distribution of Buck, so it has to be manually
built and installed.  Apache Ant is required.  Currently only Linux and Mac
OS are supported.  Gerrit's buck wrappers require Python version 2.6 or higher.

Clone the git and build it:

----
  git clone https://gerrit.googlesource.com/buck
  cd buck
  ant
----

If you don't have a `bin/` directory in your home directory, create one:

----
  mkdir ~/bin
----

Add the `~/bin` folder to the path:

----
  PATH=~/bin:$PATH
----

Note that the buck executable needs to be available in all shell sessions,
so also make sure it is appended to the path globally.

Add a symbolic link in `~/bin` to the buck executable:

----
  ln -s `pwd`/bin/buck ~/bin/
----

Verify that `buck` is accessible:

----
  which buck
----

If you plan to use the link:#buck-daemon[Buck daemon] add a symbolic
link in `~/bin` to the buckd executable:

----
  ln -s `pwd`/bin/buckd ~/bin/
----

To enable autocompletion of buck commands, install the autocompletion
script from `./scripts/bash_completion` in the buck project.  Refer to
the script's header comments for installation instructions.


[[eclipse]]
== Eclipse Integration


=== Generating the Eclipse Project

Create the Eclipse project:

----
  tools/eclipse/project.py
----

In Eclipse, choose 'Import existing project' and select the `gerrit` project
from the current working directory.

Expand the `gerrit` project, right-click on the `buck-out` folder, select
'Properties', and then under 'Attributes' check 'Derived'.

Note that if you make any changes in the project configuration
that get saved to the `.project` file, for example adding Resource
Filters on a folder, they will be overwritten the next time you run
`tools/eclipse/project.py`.


=== Refreshing the Classpath

If an updated classpath is needed, the Eclipse project can be
refreshed and missing dependency JARs can be downloaded:

----
  tools/eclipse/project.py
----


=== Attaching Sources

To save time and bandwidth source JARs are only downloaded by the buck
build where necessary to compile Java source into JavaScript using the
GWT compiler.  Additional sources may be obtained, allowing Eclipse to
show documentation or dive into the implementation of a library JAR:

----
  tools/eclipse/project.py --src
----


[[build]]
== Building on the Command Line


=== Gerrit Development WAR File

To build the Gerrit web application:

----
  buck build gerrit
----

The output executable WAR will be placed in:

----
  buck-out/gen/gerrit.war
----


=== Extension and Plugin API JAR Files

To build the extension, plugin and GWT API JAR files:

----
  buck build api
----

Java binaries, Java sources and Java docs are generated into corresponding
project directories in `buck-out/gen`, here as example for plugin API:

----
  buck-out/gen/gerrit-plugin-api/plugin-api.jar
  buck-out/gen/gerrit-plugin-api/plugin-api-src.jar
  buck-out/gen/gerrit-plugin-api/plugin-api-javadoc.jar
----

Install {extension,plugin,gwt}-api to the local maven repository:

----
  buck build api_install
----

Install gerrit.war to the local maven repository:

----
  buck build war_install
----

=== Plugins

To build all core plugins:

----
  buck build plugins:core
----

The output JAR files for individual plugins will be placed in:

----
  buck-out/gen/plugins/<name>/<name>.jar
----

The JAR files will also be packaged in:

----
  buck-out/gen/plugins/core.zip
----

To build a specific plugin:

----
  buck build plugins/<name>:<name>
----

The output JAR file will be be placed in:

----
  buck-out/gen/plugins/<name>/<name>.jar
----

Note that when building an individual plugin, the `core.zip` package
is not regenerated.

Additional plugins with BUCK files can be added to the build
environment by cloning the source repository into the plugins
subdirectory:

----
  git clone https://gerrit.googlesource.com/plugins/<name> plugins/<name>
  echo /plugins/<name> >>.git/info/exclude
----

Additional plugin sources will be automatically added to Eclipse the
next time project.py is run:

----
  tools/eclipse/project.py
----


[[documentation]]
=== Documentation

To build only the documentation:

----
  buck build docs
----

The generated html files will be placed in:

----
  buck-out/gen/Documentation/html__tmp/Documentation
----

The html files will also be bundled into `html.zip` in this location:

----
  buck-out/gen/Documentation/html.zip
----

To build the executable WAR with the documentation included:

----
  buck build withdocs
----

The WAR file will be placed in:

----
  buck-out/gen/withdocs.war
----

[[release]]
=== Gerrit Release WAR File

To build the release of the Gerrit web application, including documentation and
all core plugins:

----
  buck build release
----

The output release WAR will be placed in:

----
  buck-out/gen/release.war
----

[[tests]]
== Running Unit Tests

To run all tests including acceptance tests:

----
  buck test --all
----

To exclude slow tests:

----
  buck test --all --exclude slow
----

To run a specific test, e.g. the acceptance test
`com.google.gerrit.acceptance.git.HttpPushForReviewIT`:

----
  buck test //gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/git:HttpPushForReviewIT
----


== Dependencies

Dependency JARs are normally downloaded automatically, but Buck can inspect
its graph and download any missing JAR files.  This is useful to enable
subsequent builds to run without network access:

----
  tools/download_all.py
----

When downloading from behind a proxy (which is common in some corporate
environments), it might be necessary to explicitly specify the proxy that
is then used by `curl`:

----
  export http_proxy=http://<proxy_user_id>:<proxy_password>@<proxy_server>:<proxy_port>
----

Redirection to local mirrors of Maven Central and the Gerrit storage
bucket is supported by defining specific properties in
`local.properties`, a file that is not tracked by Git:

----
  echo download.GERRIT = http://nexus.my-company.com/ >>local.properties
  echo download.MAVEN_CENTRAL = http://nexus.my-company.com/ >>local.properties
----

The `local.properties` file may be placed in the root of the gerrit repository
being built, or in `~/.gerritcodereview/`.  The file in the root of the gerrit
repository has precedence.

== Building against unpublished Maven JARs

To build against unpublished Maven JARs, like gwtorm or PrologCafe, the custom
JARs must be installed in the local Maven repository (`mvn clean install`) and
`maven_jar()` must be updated to point to the `MAVEN_LOCAL` Maven repository for
that artifact:

[source,python]
----
 maven_jar(
   name = 'gwtorm',
   id = 'gwtorm:gwtorm:42',
   license = 'Apache2.0',
   repository = MAVEN_LOCAL,
 )
----

== Building against unpublished JARs, that change frequently

If a dependent Gerrit library is undergoing active development it must be
recompiled and the change must be reflected in the Buck build process. For
example testing Gerrit against changed JGit snapshot version. After building
JGit library, the artifacts are created in local Maven build directory, e. g.:

----
  mvn package
  /home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT.jar
  /home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT-sources.jar
----

If as usual, installation of the build artifacts takes place in local maven
repository, then the Buck build must fetch them from there with normal
`download_file.py` process. Disadvantage of this approach is that Buck cache
invalidation must occur to refresh the artifacts after next
change-compile-install round trip.

To shorten that workflow and take the installation of the artifacts to the
local Maven repository and fetching it again from there out of the picture,
`local_jar()` method is used instead of `maven_jar()`:

[source,python]
----
 local_jar(
   name = 'jgit',
   jar = '/home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT.jar',
   src = '/home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT-sources.jar',
   deps = [':ewah']
 )
----

This creates a symlink to the Buck targets direct against artifacts in
another project's Maven target directory:

----
  buck-out/gen/lib/jgit/jgit.jar ->
  /home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT.jar
----

== Building against artifacts from custom Maven repositories

To build against custom Maven repositories, two modes of operations are
supported: with rewrite in local.properties and without.

Without rewrite the URL of custom Maven repository can be directly passed
to the maven_jar() function:

[source,python]
----
  GERRIT_FORGE = 'http://gerritforge.com/snapshot'

  maven_jar(
    name = 'gitblit',
    id = 'com.gitblit:gitblit:1.4.0',
    sha1 = '1b130dbf5578ace37507430a4a523f6594bf34fa',
    license = 'Apache2.0',
    repository = GERRIT_FORGE,
 )
----

When the custom URL has to be rewritten, then the same logic as with Gerrit
known Maven repository is used: Repo name must be defined that matches an entry
in local.properties file:

----
  download.GERRIT_FORGE = http://my.company.mirror/gerrit-forge
----

And corresponding BUCK excerpt:

[source,python]
----
  GERRIT_FORGE = 'GERRIT_FORGE:'

  maven_jar(
    name = 'gitblit',
    id = 'com.gitblit:gitblit:1.4.0',
    sha1 = '1b130dbf5578ace37507430a4a523f6594bf34fa',
    license = 'Apache2.0',
    repository = GERRIT_FORGE,
 )
----

=== Caching Build Results

Build results can be locally cached, saving rebuild time when
switching between Git branches. Buck's documentation covers
caching in link:http://facebook.github.io/buck/concept/buckconfig.html[buckconfig].
The trivial case using a local directory is:

----
  cat >.buckconfig.local <<EOF
  [cache]
    mode = dir
    dir = buck-cache
  EOF
----

[[buck-daemon]]
=== Using Buck daemon

Buck ships with a daemon command `buckd`, which uses the
link:https://github.com/martylamb/nailgun[Nailgun] protocol for running
Java programs from the command line without incurring the JVM startup
overhead.

Using a Buck daemon can save significant amounts of time as it avoids the
overhead of starting a Java virtual machine, loading the buck class files
and parsing the build files for each command.

It is safe to run several buck daemons started from different project
directories and they will not interfere with each other. Buck's documentation
covers daemon in http://facebook.github.io/buck/command/buckd.html[buckd].

The trivial use case is to run `buckd` from the project's root directory and
run `buck` as usual:

----
  buckd
  buck build gerrit
  Using buckd.
  [-] PARSING BUILD FILES...FINISHED 0.6s
  [-] BUILDING...FINISHED 0.2s
----

=== Override Buck's settings

Additional JVM args for Buck can be set in `.buckjavaargs` in the
project root directory. For example to override Buck's default 1GB
heap size:

----
  cat > .buckjavaargs <<EOF
  -XX:MaxPermSize=512m -Xms8000m -Xmx16000m
  EOF
----

== Rerun unit tests

If for some reasons tests, that were already run must be repeated, unit test
cache must be removed fist. That's because the test execution results are
cached by Buck:

----
  $ rm -rf buck-out/bin/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/group/.AddRemoveGroupMembersIT/
----

After clearing the cache test can be rerun again:

----
  $ buck test //gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/group:AddRemoveGroupMembersIT
  TESTING //gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/group:AddRemoveGroupMembersIT
  PASS  14,9s  8 Passed   0 Failed   com.google.gerrit.acceptance.rest.group.AddRemoveGroupMembersIT
  TESTS PASSED
----

An alternative approach is to use a Buck feature:
--test-selectors (-filters, -f) option:

----
  buck test --all -f 'com.google.gerrit.acceptance.rest.change.SubmitByMergeAlwaysIT'
  TESTING SELECTED TESTS
  PASS  14,5s  6 Passed   0 Failed   com.google.gerrit.acceptance.rest.change.SubmitByMergeAlwaysIT
  TESTS PASSED
----

When this option is used, cache is disabled per design and doesn't need to be deleted.
Note: when -f option is used, the whole unit test cache is dropped. As a consequence,
repeating the

----
buck test --all
----

would re-execute all tests again.

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