Guidelines for reviewing JiHu (JH) Edition related merge requests

We have two kinds of changes related to JH:

Inside jh/
- This is beyond EE repository and not the intention for this documentation.
Outside jh/
- These will have to sit in EE repository, so reviewers and maintainers for EE repository will have to review and maintain. This includes codes like Gitlab.jh?, and how it attempts to load codes under jh/ just like we have codes which will load codes under ee/.
- This documentation intended to guide how those codes should look like, so we'll have better understanding what are the changes needed for looking up codes under jh/.
- We will generalize this so both EE and JH can share the same mechanism, then we wouldn't have to treat them differently.
- Database migrations and database schema changes which are required to support running JH edition. See JiHu guidelines for database changes for details.

If needed, review the corresponding JH merge request located at JH repository.

When to merge files to the GitLab Inc. repository

Files that are added to the GitLab JH repository outside of jh/ must be mirrored in the GitLab Inc. repository.

If code that is added to the GitLab Inc. repository references (for example, render_if_exists) any GitLab JH file that does not exist in the GitLab Inc. codebase, add a comment with a link to the JiHu merge request or file. This is to prevent the reference from being misidentified as a missing partial and subsequently deleted in the gitlab codebase.

Process overview

Read the following process guides:

Act as EE when `jh/` does not exist or when `EE_ONLY=1`

In the case of EE repository, jh/ does not exist so it should just act like EE (or CE when the license is absent)
In the case of JH repository, jh/ does exist but EE_ONLY environment variable can be set to force it run under EE mode.

Act as FOSS when `FOSS_ONLY=1`

In the case of JH repository, jh/ does exist but FOSS_ONLY environment variable can be set to force it run under FOSS (CE) mode.

CI pipelines in a JH context

EE repository does not have jh/ directory therefore there is no way to run JH pipelines in the EE repository. All JH tests should go to JH repository.

The top-level JH CI configuration is located at jh/.gitlab-ci.yml (which does not exist in EE repository) and it'll include EE CI configurations accordingly. Sometimes it's needed to update the EE CI configurations for JH to customize more easily.

JH features based on CE or EE features

For features that build on existing CE/EE features, a module in the JH namespace injected in the CE/EE class/module is needed. This aligns with what we're doing with EE features.

See Extend CE features with EE backend code for more details.

For example, to prepend a module into the User class you would use the following approach:

class User < ActiveRecord::Base
  # ... lots of code here ...
end

User.prepend_mod

Under EE, User.prepend_mod will attempt to:

Load EE module

Under JH, User.prepend_mod will attempt to:

Load EE module, and:
Load JH module

Do not use methods such as prepend, extend, and include. Instead, use prepend_mod, extend_mod, or include_mod. These methods will try to find the relevant EE and JH modules by the name of the receiver module.

If reviewing the corresponding JH file is needed, it should be found at JH repository.

NOTE: In some cases, JH does need to override something we don't need, and in that case it is ok to also add prepend_mod for the modules. When we do this, also add a comment mentioning it, and a link to the JH module using it. This way we know where it's used and when we might not need it anymore, and we do not remove them only because we're not using it, accidentally breaking JH. An example of this:

# Added for JiHu
# Used in https://jihulab.com/gitlab-cn/gitlab/-/blob/main-jh/jh/lib/jh/api/integrations.rb
API::Integrations.prepend_mod

General guidance for writing JH extensions

See Guidelines for implementing Enterprise Edition features for general guidance.