As part of the code review process, reviewers score each change with values for each label configured for the project. The label values that a given user is allowed to set are defined according to the access controls. Gerrit comes pre-configured with the Code-Review label that can be granted to groups within projects, enabling functionality for that group’s members. Project owners and admins might also need to configure rules which require labels to be voted before a change can be submittable. See the submit requirements documentation to configure such rules.

Sticky Votes

Whether votes are sticky when a new patch set is created depends on the copyCondition of the label. If an approval matches the configured condition it is copied from the old current patch set to the new current patch set. Votes that are not copied to the new patch set, are called outdated.

If votes get outdated due to pushing a new patch set the uploader is informed about this by a message in the git output. In addition, outdated votes are also listed in the email notification that is sent for the new patch set (unless this is disabled by a custom email template). Note, that the uploader only get this email notification if they have configured Every Comment for Email notifications in their user preferences. With any other email preference the email sender, the uploader in this case, is not included in the email recipients.

If votes get outdated due to creating a new patch set the user of the removed vote is added to the attention set of the change, as they need to re-review the change and renew their vote.

If a vote is applied on an outdated patch set (i.e. a patch set that is not the current patch set) the vote is copied forward to follow-up patch sets if possible. A newly added or updated vote on an outdated patch set is copied to follow-up patch sets if:

  • the vote is copyable (i.e. it matches the copyCondition of the label)

  • neither the follow-up patch set nor an intermediate patch set has a non-copied vote or a deletion vote (vote with value 0) that overrides the copy vote

If an approval on an outdated patch set is removed or updated to a value that is not copyable, existing copies of that approval on follow-up patch sets are removed.

Label: Code-Review

The Code-Review label is configured upon the creation of a Gerrit instance. It may have any meaning the project desires. It was originally invented by the Android Open Source Project to mean 'I read the code and it seems reasonably correct'.

The range of values is:

  • -2 This shall not be submitted

    The code is so horribly incorrect/buggy/broken that it must not be submitted to this project, or to this branch. This value is valid across all patch sets in the same change, i.e. the reviewer must actively change his/her review to something else before the change is submittable.

    Any -2 blocks submit.

  • -1 I would prefer this is not submitted as is

    The code doesn’t look right, or could be done differently, but the reviewer is willing to live with it as-is if another reviewer accepts it, perhaps because it is better than what is currently in the project. Often this is also used by contributors who don’t like the change, but also aren’t responsible for the project long-term and thus don’t have final say on change submission.

    Does not block submit.

  • 0 No score

    Didn’t try to perform the code review task, or glanced over it but don’t have an informed opinion yet.

  • +1 Looks good to me, but someone else must approve

    The code looks right to this reviewer, but the reviewer doesn’t have access to the +2 value for this category. Often this is used by contributors to a project who were able to review the change and like what it is doing, but don’t have final approval over what gets submitted.

  • +2 Looks good to me, approved

    Basically the same as +1, but for those who have final say over how the project will develop.

    Any +2 enables submit.

For a change to be submittable, the latest patch set must have a +2 Looks good to me, approved in this category, and no -2 This shall not be submitted. Thus -2 on any patch set can block a submit, while +2 on the latest patch set can enable it.

If a Gerrit installation does not wish to use this label in any project, the [label "Code-Review"] section can be deleted from project.config in All-Projects.

If a Gerrit installation or project wants to modify the description text associated with these label values, the text can be updated in the label.Code-Review.value fields in project.config.

Additional entries could be added to label.Code-Review.value to further extend the negative and positive range, but there is likely little value in doing so as this only expands the middle region. This label is a MaxWithBlock type, which means that the lowest negative value if present blocks a submit, while the highest positive value is required to enable submit.

Label: Verified

The Verified label was originally invented by the Android Open Source Project to mean 'compiles, passes basic unit tests'. Some CI tools expect to use the Verified label to vote on a change after running.

During site initialization the administrator may have chosen to configure the default Verified label for all projects. In case it is desired to configure it at a later time, administrators can do this by adding the following to project.config in All-Projects:

  [label "Verified"]
      function = MaxWithBlock
      value = -1 Fails
      value = 0 No score
      value = +1 Verified
      copyCondition = changekind:NO_CODE_CHANGE

The range of values is:

  • -1 Fails

    Tried to compile, but got a compile error, or tried to run tests, but one or more tests did not pass.

    Any -1 blocks submit.

  • 0 No score

    Didn’t try to perform the verification tasks.

  • +1 Verified

    Compiled (and ran tests) successfully.

    Any +1 enables submit.

For a change to be submittable, the change must have a +1 Verified in this label, and no -1 Fails. Thus, -1 Fails can block a submit, while +1 Verified enables a submit.

Additional values could also be added to this label, to allow it to behave more like Code-Review (below). Add -2 and +2 entries to the label.Verified.value fields in project.config to get the same behavior.

Customized Labels

Site administrators and project owners can define their own labels, or customize labels inherited from parent projects.

See above for descriptions of how Verified and Code-Review work, and add your own label to project.config to get the same behavior over your own range of values, for any label you desire.

Just like the built-in labels, users need to be given permissions to vote on custom labels. Permissions can either be added by manually editing project.config when adding the labels, or, once the labels are added, permission categories for those labels will show up in the permission editor web UI.

Labels may be added to any project’s project.config; the default labels are defined in All-Projects.

Inheritance

Labels are inherited from parent projects. A child project may add, override, or remove labels defined in its parents.

Overriding a label in a child project overrides all its properties and values. It is not possible to modify an inherited label by adding properties in the child project’s configuration; all properties from the parent definition must be redefined in the child.

To remove a label in a child project, add an empty label with a single "0" value, with the same name as in the parent. This will override the parent label with a label containing the defaults (function = NoBlock, defaultValue = 0 and no further allowed values)

Layout

Labels are laid out in alphabetical order.

label.Label-Name

The name for a label, consisting only of alphanumeric characters and -.

label.Label-Name.description

The label description. This field can provide extra information of what the label is supposed to do.

label.Label-Name.value

A multi-valued key whose values are of the form "<#> Value description text". The <#> may be any positive or negative number with an optional leading +.

label.Label-Name.defaultValue

The default value (or score) for the label. The defaultValue must be within the range of valid label values. It is an optional label setting, if not defined the defaultValue for the label will be 0. When a defaultValue is defined, that value will get set in the Reply dialog by default.

A defaultValue can be set to a score that is outside of the permissible range for a user. In that case the score that will get set in the Reply box will be either the lowest or highest score in the permissible range.

label.Label-Name.function (deprecated)

Label functions dictate the rules for requiring certain label votes before a change is allowed for submission. Label functions are deprecated and updates that set function to a blocking value {MaxWithBlock, MaxNoBlock, AnyWithBlock} will be rejected. Existing label function definitions can only be updated to {NoBlock, NoOp, PatchSetLock}. New label defintions should also explicitly set the function attribute to a non-blocking value since the default is MaxWithBlock.

If your project has a blocking label function, we highly encourage you to change it to NoBlock and add a submit-requirement for the same label. See the submit-requirements documentation for more details.

The name of a function for evaluating multiple votes for a label. This function is only applied if the default submit rule is used for a label. If you write a custom submit rule (and do not call the default rule), the function name is ignored and may be treated as optional.

Valid values are:

  • MaxWithBlock (default)

    The lowest possible negative value, if present, blocks a submit, while the highest possible positive value is required to enable submit. There must be at least one positive value, or else submit will never be enabled. To permit blocking submits, ensure a negative value is defined.

  • AnyWithBlock

    The label is not mandatory but the lowest possible negative value, if present, blocks a submit. To permit blocking submits, ensure that a negative value is defined.

  • MaxNoBlock

    The highest possible positive value is required to enable submit, but the lowest possible negative value will not block the change.

  • NoBlock/NoOp

    The label is purely informational and values are not considered when determining whether a change is submittable.

  • PatchSetLock

    The PatchSetLock function provides a locking mechanism for patch sets. This function’s values are not considered when determining whether a change is submittable. When set, no new patchsets can be created and rebase and abandon are blocked. This is useful to prevent updates to a change while (potentially expensive) CI validation is running.

    This function is designed to allow overlapping locks, so several lock accounts could lock the same change.

    Allowed range of values are 0 (Patch Set Unlocked) to 1 (Patch Set Locked).

label.Label-Name.allowPostSubmit

If true, the label may be voted on for changes that have already been submitted. If false, the label will not appear in the UI and will not be accepted when reviewing a closed change.

In either case, voting on a label after submission is only permitted if the new vote is at least as high as the old vote by that user. This avoids creating the false impression that a post-submit vote can change the past and affect submission somehow.

Defaults to true.

label.Label-Name.copyCondition

If set, Gerrit matches patch set approvals against the provided query string. If the query matches, the approval is copied from one patch set to the next. The query language is the same as for other queries.

This logic is triggered whenever a new patch set is uploaded.

Gerrit currently supports the following predicates:

changekind:{NO_CHANGE,NO_CODE_CHANGE,MERGE_FIRST_PARENT_UPDATE,REWORK,TRIVIAL_REBASE}

Matches if the diff between two patch sets was of a certain change kind:

  • NO_CHANGE:

    Matches when a new patch set is uploaded that has the same parent tree, code delta, and commit message as the previous patch set. This means that only the patch set SHA-1 is different. This can be used to enable sticky approvals, reducing turn-around for this special case.

    It is recommended to leave this enabled for both, the Code-Review and the Verified labels.

    NO_CHANGE is more trivial than a trivial rebase, no code change and a first parent update, hence this change kind is also matched by changekind:TRIVIAL_REBASE, changekind:NO_CODE_CHANGE and if it’s a merge commit by changekind:MERGE_FIRST_PARENT_UPDATE.

  • NO_CODE_CHANGE:

    Matches when a new patch set is uploaded that has the same parent tree as the previous patch set and the same code diff (including context lines) as the previous patch set. This means only the commit message may be different; the change hasn’t even been rebased. Also matches if the commit message is not different, which means this includes matching patch sets that have NO_CHANGE as the change kind.

    This predicate can be used to enable sticky approvals on labels that only depend on the code, reducing turn-around if only the commit message is changed prior to submitting a change.

    For the Verified label that is optionally installed by the init site program this predicate is used by default.

  • MERGE_FIRST_PARENT_UPDATE:

    Matches when a new patch set is uploaded that is a new merge commit which only differs from the merge commit in the previous patch set in its first parent, or has identical parents (aka the change kind of the merge commit is NO_CHANGE).

    The first parent of the merge commit is part of the change’s target branch, whereas the other parent(s) refer to the feature branch(es) to be merged.

    Matching this change kind is useful if you don’t want to trigger CI or human verification again if your target branch moved on but the feature branch(es) being merged into the target branch did not change.

    This predicate does not match if the patch set is not a merge commit.

  • TRIVIAL_REBASE:

    Matches when a new patch set is uploaded that is a trivial rebase. A new patch set is considered to be trivial rebase if the commit message is the same as in the previous patch set and if it has the same diff (including context lines) as the previous patch set. This is the case if the change was rebased onto a different parent and that rebase did not require git to perform any conflict resolution, or if the parent did not change at all (aka the change kind of the commit is NO_CHANGE).

    This predicate can be used to enable sticky approvals, reducing turn-around for trivial rebases prior to submitting a change.

    For the pre-installed Code-Review label this predicate is used by default.

  • REWORK:

    Matches all kind of change kinds because any other change kind is just a more trivial version of a rework. This means setting changekind:REWORK is equivalent to setting is:ANY.

is:{MIN,MAX,ANY}

Matches approvals that have a minimal, maximal or any score:

  • MIN:

    Matches approvals that have a minimal score, i.e. the lowest possible (negative) value for this label.

  • MAX:

    Matches approvals that a maximal score, i.e. the highest possible (positive) value for this label.

  • ANY:

    Matches any approval when a new patch set is uploaded.

is:'VALUE'

Matches approvals that have a voting value that is equal to 'VALUE'.

Negative values need to be quoted, e.g.: is:"-1"

approverin:{group-id}

Matches votes granted by a user who is a member of {group-id}.

uploaderin:{group-id}

Matches all votes if the new patch set was uploaded by a member of {group-id}.

has:unchanged-files

Matches when the new patch-set has the same list of files as the previous patch-set.

Votes are not copied in the following cases:

  • If one more files are renamed in the new patch set. These files are counted as a deletion of the file at the old path and an addition of the file at the new path. This means the list of files did change.

  • If one or more files are reverted to their original content, that is files that become same as in the base revision.

This predicate is useful if you don’t want to trigger CI or human verification again if the list of files didn’t change.

Note, "unchanged-files" is the only value that is supported for the "has" operator.

Group ID

Some predicates (approverin, uploaderin) expect a group ID as value. This group ID can be any of the group identifiers that are supported in the REST API: group UUID, group ID (for Gerrit internal groups only) and group name

It’s preferred to reference groups by UUID, rather than name. Referencing groups by name is not recommended because:

  • Groups may be renamed and then the group reference can no longer be resolved. If this happens another group with different members can take over the group name, so that exemptions which have been granted by this predicate apply to the other group. This is a security concern.

  • Group names that contain spaces are not supported.

  • Ambiguous group names cannot be resolved. This means if another group with the same name gets created at a later point in time, the group name can no longer be resolved and the predicate breaks.

Using the group UUID has a small drawback though, since it makes the condition less human-readable.

Example

copyCondition = is:MIN OR -change-kind:REWORK OR uploaderin:dead...beef

label.Label-Name.canOverride

If false, the label cannot be overridden by child projects. Any configuration for this label in child projects will be ignored. Defaults to true.

label.Label-Name.branch

By default a given project’s label applicable scope is all changes on all branches of this project and its child projects.

Label’s applicable scope can be branch specific via configuration. E.g. create a label Video-Qualify on parent project and configure the branch as:

  [label "Video-Qualify"]
      branch = refs/heads/video-1.0/*
      branch = refs/heads/video-1.1/Kino

Then only changes in above branch scope of parent project and child projects will be affected by Video-Qualify.

Note
 The branch is independent from the branch scope defined in access parts in project.config file. That means from the UI a user can always assign permissions for that label on a branch, but this permission is then ignored if the label doesn’t apply for that branch. Additionally, the branch modifier has no effect when the submit rule is customized in the rules.pl of the project or inherited from parent projects. Branch can be a ref pattern similar to what is documented here, but must not contain ${username} or ${shardeduserid}.

label.Label-Name.ignoreSelfApproval (deprecated)

If true, the label may be voted on by the uploader of the latest patch set, but their approval does not make a change submittable. Instead, a non-uploader who has the right to vote has to approve the change.

Defaults to false.

The ignoreSelfApproval attribute is deprecated, favour using submit requirements and define the submittableIf expression with the label operator and the user=non_uploader argument. See the Code Review submit requirement example.

Example

To define a new 3-valued category that behaves exactly like Verified, but has different names/labels:

  [label "Copyright-Check"]
      function = MaxWithBlock
      value = -1 Do not have copyright
      value = 0 No score
      value = +1 Copyright clear

The new column will appear at the end of the table, and -1 Do not have copyright will block submit, while +1 Copyright clear is required to enable submit.

Default Value Example

This example attempts to describe how a label default value works with the user permissions. Assume the configuration below.

  [access "refs/heads/*"]
      label-Snarky-Review = -3..+3 group Administrators
      label-Snarky-Review = -2..+2 group Project Owners
      label-Snarky-Review = -1..+1 group Registered Users
  [label "Snarky-Review"]
      value = -3 Ohh, hell no!
      value = -2 Hmm, I'm not a fan
      value = -1 I'm not sure I like this
      value = 0 No score
      value = +1 I like, but need another to like it as well
      value = +2 Hmm, this is pretty nice
      value = +3 Ohh, hell yes!
      defaultValue = -3

Upon clicking the Reply button:

  • Administrators have all scores (-3..+3) available, -3 is set as the default.

  • Project Owners have limited scores (-2..+2) available, -2 is set as the default.

  • Registered Users have limited scores (-1..+1) available, -1 is set as the default.

Patch Set Lock Example

This example shows how a label can be configured to have a standard patch set lock.

  [access "refs/heads/*"]
      label-Patch-Set-Lock = +0..+1 group Administrators
  [label "Patch-Set-Lock"]
      function = PatchSetLock
      value =  0 Patch Set Unlocked
      value = +1 Patch Set Locked
      defaultValue = 0

Part of Gerrit Code Review