Prior to invoking the submit_rule(X) query for a change, Gerrit initializes the Prolog engine with a set of facts (current data) about this change. The following table provides an overview of the provided facts.

Important
 All the terms listed below are defined in the gerrit package. To use any of them we must use a qualified name like gerrit:change_branch(X).
Table 1. Prolog facts about the current change
Fact Example Description

change_branch/1

change_branch('refs/heads/master').

Destination Branch for the change as string atom

change_owner/1

change_owner(user(1000000)).

Owner of the change as user(ID) term. ID is the numeric account ID

change_project/1

change_project('full/project/name').

Name of the project as string atom

change_topic/1

change_topic('plugins').

Topic name as string atom

commit_author/1

commit_author(user(100000)).

Author of the commit as user(ID) term. ID is the numeric account ID

commit_author/3

commit_author(user(100000), 'John Doe', 'john.doe@example.com').

ID, full name and the email of the commit author. The full name and the email are string atoms

commit_committer/1

commit_committer()

Committer of the commit as user(ID) term. ID is the numeric account ID

commit_committer/3

commit_committer()

ID, full name and the email of the commit committer. The full name and the email are string atoms

commit_label/2

commit_label(label('Code-Review', 2), user(1000000)).

Set of votes on the last patch-set

commit_label(label('Verified', -1), user(1000001)).

commit_message/1

commit_message('Fix bug X').

Commit message as string atom

current_user/1

current_user(user(1000000)).

Current user as one of the four given possibilities

current_user(user(anonymous)).

current_user(user(peer_daemon)).

current_user(user(replication)).

In addition Gerrit provides a set of built-in helper predicates that can be used when implementing the submit_rule predicate. The most common ones are listed in the following table.

Table 2. Built-in Prolog helper predicates
Predicate Example usage Description

commit_delta/1

commit_delta('\\.java$').

True if any file name from the last patch set matches the given regex.

commit_delta/3

commit_delta('\\.java$', T, P)

Returns the change type (via T) and path (via P), if the change type is rename, it also returns the old path. If the change type is rename, it returns a delete for old path and an add for new path. If the change type is copy, an add is returned along with new path.

Possible values for the change type are the following symbols: add, modify, delete, rename, copy

commit_delta/4

commit_delta('\\.java$', T, P, O)

Like commit_delta/3 plus the old path (via O) if applicable.

commit_edits/2

commit_edits('/pom.xml$', 'dependency')

True if any of the files matched by the file name regex (first parameter) have edited lines that match the regex in the second parameter. This example will be true if there is a modification of a pom.xml file such that an edited line contains or contained the string 'dependency'.

commit_message_matches/1

commit_message_matches('^Bug fix')

True if the commit message matches the given regex.
Note
 for a complete list of built-in helpers read the gerrit_common.pl and all Java classes whose name matches PRED_*.java from Gerrit’s source code.

Part of Gerrit Code Review