Redmine

Patches for Redmine 5.0 or later (Rails 6.1 or later) are available here(tested in r22282).

Making plugins as gems allows you to install all plugins at once by listing them in the Gemfile.extension and running bundle install.
This can be especially useful in a Docker environment where you don't need to create a separate script to install plugins.
On the other hand, plugins placed under plugins/ directory will still work. I will refer to current plugins as "filesystem plugin" and gemified plugins as "gem plugin".

If there's a "filesystem plugin" and a "gem plugin" with the same ID, the "filesystem plugin" takes priority
To install a "gem plugin", add its name to Gemfile.extension. Note that the reason why Gemfile.extension is not named Gemfile.plugin is that we assume that themes will also be gemmed in the future.

For a "gem plugin", the plugin information is divided into two files: init.rb and gemspec. Basic information like plugin name and author goes in gemspec, while Redmine-specific information like menus and settings stays in init.rb.

As a trial, I converted redmine-view-customize into a "gem plugin". It works well. https://github.com/tohosaku/redmine-view-customize/tree/rubygems
The gem name, Redmine plugin ID, git repository name, and class names under the lib directory do not need to match. However, you can match all of them.

On the other hand, if you try to register a plugin with a different gem name and the same plugin id, an error will occur.

Differences from the previous version¶

"filesystem plugin" allowed adding a gem to Redmine itself by adding the gem in the plugin's Gemfile. This is because Redmine was reading each plugin's Gemfile and requiring it as a dependent gem of redmine itself. gem plugin requires an add_runtime_dependency to be listed in each gemspec. The dependencies are automatically loaded when the plugin is registered with Redmine.

Creating a new plugin¶

bin/rails g redmine_plugin_gem foo

Notes on gemspec for "gem plugin"¶

• In the gemspec file, Do not use variables, constants, etc. defined by gem (eg. Foo::VERSION). gemspec is evaluated before rails initialization is completed. redmine plugin variables and constants are supposed to be managed by the zeitwerk autoloader after rails is started, so using them at initialization time will cause errors.
• Redmine plugin dependencies can also be described in gemspec using "add_runtime_dependency".
• The spec.metadata["redmine_plugin_id"] = "plugin id" is required as metadata in gemspec.
• The following attributes that were previously listed in init.rb will be overwritten by the corresponding attributes in gemspec.

UI Changes¶

Added the ability to distinguish "gem plugin" or not in the list of plugins.

How to develop “filesystem plugin” and “gem plugin” in one development branch¶

• Place the gem plugin directory in the plugins directory, and enter the gem information required by the "filesystem plugin" for Redmine 4.2 and Redmine 5.0 in the PluginGemfile. Gemfile is ignored. Dependent gem information must be included in both the PluginGemfile and gemspec.
• To create a plugin that works with both Redmine 4.2 and Redmine 5.0 or later, the init.rb must look like this

if Rails.version > '6.0' && Rails.autoloaders.zeitwerk_enabled?
    # for Redmine5.0 or later
else
  Rails.configuration.to_prepare do
    # for Redmine4.*
  end
end

Updated patch 0001, can be applied to r22583