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Code Owners (STARTER)

Introduction

When contributing to a project, it can often be difficult to find out who should review or approve merge requests. Additionally, if you have a question over a specific file or code block, it may be difficult to know who to find the answer from.

GitLab Code Owners is a feature to define who owns specific files or paths in a repository, allowing other users to understand who is responsible for each file or path.

Why is this useful?

Code Owners allows for a version controlled, single source of truth file outlining the exact GitLab users or groups that own certain files or paths in a repository. Code Owners can be utilized in the merge request approval process which can streamline the process of finding the right reviewers and approvers for a given merge request.

In larger organizations or popular open source projects, Code Owners can also be useful to understand who to contact if you have a question that may not be related to code review or a merge request approval.

How to set up Code Owners

You can use a CODEOWNERS file to specify users or shared groups that are responsible for specific files and directories in a repository.

You can choose to add the CODEOWNERS file in three places:

  • To the root directory of the repository
  • Inside the .gitlab/ directory
  • Inside the docs/ directory

The CODEOWNERS file is scoped to a branch, which means that as new files are introduced, the user adding the new content can specify themselves as a code owner, all before the new changes get merged to the target branch.

When a file matches multiple entries in the CODEOWNERS file, the users from last pattern matching the file are displayed on the blob page of the given file. For example, you have the following CODEOWNERS file:

README.md @user1

# This line would also match the file README.md
*.md @user2

The user that would show for README.md would be @user2.

Approvals by Code Owners

Once you've added Code Owners to a project, you can configure it to be used for merge request approvals:

NOTE: Note: Developer or higher permissions are required in order to approve a merge request.

Once set, Code Owners are displayed in merge requests widgets:

MR widget - Code Owners

While the CODEOWNERS file can be used in addition to Merge Request Approval Rules, it can also be used as the sole driver of merge request approvals (without using Approval Rules). To do so, create the file in one of the three locations specified above and set the code owners as required approvers for protected branches. Use the syntax of Code Owners files to specify the actual owners and granular permissions.

Using Code Owners in conjunction with Protected Branches will prevent any user who is not specified in the CODEOWNERS file from pushing changes for the specified files/paths, even if their role is included in the Allowed to push column. This allows for a more inclusive push strategy, as administrators don't have to restrict developers from pushing directly to the protected branch, but can restrict pushing to certain files where a review by Code Owners is required.

The syntax of Code Owners files

Files can be specified using the same kind of patterns you would use in the .gitignore file followed by one or more of:

  • A user's @username.
  • A user's email address.
  • The @name of one or more groups that should be owners of the file.
  • Lines starting with # are escaped.

The order in which the paths are defined is significant: the last pattern that matches a given path will be used to find the code owners.

Groups as Code Owners

Groups and subgroups members are inherited as eligible Code Owners to a project, as long as the hierarchy is respected.

For example, consider a given group called "Group X" (slug group-x) and a "Subgroup Y" (slug group-x/subgroup-y) that belongs to the Group X, and suppose you have a project called "Project A" within the group and a "Project B" within the subgroup.

The eligible Code Owners to Project B are both the members of the Group X and the Subgroup Y. And the eligible Code Owners to the Project A are just the members of the Group X, given that Project A doesn't belong to the Subgroup Y:

Eligible Code Owners

But you have the option to invite the Subgroup Y to the Project A so that their members also become eligible Code Owners:

Invite subgroup members to become eligible Code Owners

Once invited, any member (@user) of the group or subgroup can be set as Code Owner to files of the Project A or B, as well as the entire Group X (@group-x) or Subgroup Y (@group-x/subgroup-y), as exemplified below:

# A member of the group or subgroup as Code Owner to a file
file.md @user

# All group members as Code Owners to a file
file.md @group-x

# All subgroup members as Code Owners to a file
file.md @group-x/subgroup-y

# All group and subgroup members as Code Owners to a file
file.md @group-x @group-x/subgroup-y

Code Owners Sections (PREMIUM)

Code Owner rules can be grouped into named sections. This allows for better organization of broader categories of Code Owner rules to be applied. Additionally, the usual guidance that only the last pattern matching the file is applied is expanded such that the last pattern matching for each section is applied.

For example, in a large organization, independent teams may have a common interest in parts of the application, for instance, a payment processing company may have "development", "security", and "compliance" teams looking after common parts of the codebase. All three teams may need to approve changes. Although approval rules make this possible, they apply to every merge request. Also, while Code Owners are applied based on which files are changed, only one CODEOWNERS pattern can match per file path.

Using CODEOWNERS sections allows multiple teams that only need to approve certain changes, to set their own independent patterns by specifying discrete sections in the CODEOWNERS file. The section rules may be used for shared paths so that multiple teams can be added as reviewers.

Sections can be added to CODEOWNERS files as a new line with the name of the section inside square brackets. Every entry following it is assigned to that section. The following example would create 2 Code Owner rules for the "README Owners" section:

[README Owners]
README.md @user1 @user2
internal/README.md @user2

Multiple sections can be used, even with matching file or directory patterns. Reusing the same section name will group the results together under the same section, with the most specific rule or last matching pattern being used. For example, consider the following entries in a CODEOWNERS file:

[Documentation]
ee/docs    @gl-docs
docs       @gl-docs

[Database]
README.md  @gl-database
model/db   @gl-database

[DOCUMENTATION]
README.md  @gl-docs

This will result in 3 entries under the "Documentation" section header, and 2 entries under "Database". Case is not considered when combining sections, so in this example, entries defined under the sections "Documentation" and "DOCUMENTATION" would be combined into one, using the case of the first instance of the section encountered in the file.

When assigned to a section, each code owner rule displayed in merge requests widget is sorted under a "section" label. In the screenshot below, we can see the rules for "Groups" and "Documentation" sections:

MR widget - Sectional Code Owners

Example CODEOWNERS file

# This is an example of a code owners file
# lines starting with a `#` will be ignored.

# app/ @commented-rule

# We can specify a default match using wildcards:
* @default-codeowner

# We can also specify "multiple tab or space" separated codeowners:
* @multiple @code @owners

# Rules defined later in the file take precedence over the rules
# defined before.
# This will match all files for which the file name ends in `.rb`
*.rb @ruby-owner

# Files with a `#` can still be accessed by escaping the pound sign
\#file_with_pound.rb @owner-file-with-pound

# Multiple codeowners can be specified, separated by spaces or tabs
# In the following case the CODEOWNERS file from the root of the repo
# has 3 code owners (@multiple @code @owners)
CODEOWNERS @multiple @code @owners

# Both usernames or email addresses can be used to match
# users. Everything else will be ignored. For example this will
# specify `@legal` and a user with email `janedoe@gitlab.com` as the
# owner for the LICENSE file
LICENSE @legal this_does_not_match janedoe@gitlab.com

# Group names can be used to match groups and nested groups to specify
# them as owners for a file
README @group @group/with-nested/subgroup

# Ending a path in a `/` will specify the code owners for every file
# nested in that directory, on any level
/docs/ @all-docs

# Ending a path in `/*` will specify code owners for every file in
# that directory, but not nested deeper. This will match
# `docs/index.md` but not `docs/projects/index.md`
/docs/* @root-docs

# This will make a `lib` directory nested anywhere in the repository
# match
lib/ @lib-owner

# This will only match a `config` directory in the root of the
# repository
/config/ @config-owner

# If the path contains spaces, these need to be escaped like this:
path\ with\ spaces/ @space-owner

# Code Owners section:
[Documentation]
ee/docs    @gl-docs
docs       @gl-docs

[Database]
README.md  @gl-database
model/db   @gl-database

# This section will be joined with the [Documentation] section previously defined:
[DOCUMENTATION]
README.md  @gl-docs