redmine_acts_as_taggable_on

redmine_acts_as_taggable_on is a gem which allows multiple Redmine plugins to use the tables provided by acts_as_taggable_on without stepping on each others' toes.

How it works

The problem we ran into when we discovered that both redmine_tags and redmine_knowledgebase want to use the acts_as_taggable_on gem is that after either is installed, the migration for the other fails, since the database tables already exist.

Additionally, the plugins must choose between two less than ideal options when uninstalling:

• Drop the tables, destroying data which may still be in use by another plugin
• Leave the tables there, violating the user's expectation that the database should be back to how it was before the plugin was installed

redmine_acts_as_taggable_on solves this issue by giving Redmine plugins a mechanism to declare that they require these tables, and providing intelligent migrations which only drop the tables when no other plugins are using them.

redmine_acts_as_taggable_on also provides a limited defence against plugins which directly depend on acts-as-taggable-on by grepping through their Gemfiles for the string acts-as-taggable-on, and treating them the same way as plugins which use this gem, together with a gentle(-ish) suggestion to use this gem instead.

Status

Believed to be stable; not extensively tested in the wild.

Limitations

This plugin cannot currently protect against situations where a plugin directly using acts-as-taggable-on has put the generated migration into its db/migrate, and the Redmine admin tries to uninstall it.

I'm in two minds about whether to fix this: one the one hand, it would require some nasty hackery, and it's no worse than the current situation. On the other, losing one's data is not fun.

Setup

Add it to your plugin's Gemfile:

gem 'redmine_acts_as_taggable_on', '~> 0.1'

Add the migration:

echo 'class AddTagsAndTaggings < RedmineActsAsTaggableOn::Migration; end' \
    > db/migrate/001_add_tags_and_taggings.rb

Declare that your plugin needs redmine_acts_as_taggable_on inside init.rb:

require 'redmine_acts_as_taggable_on/initialize'

Redmine::Plugin.register :my_plugin do
  requires_acts_as_taggable_on
  ...

That's it. Your plugin should now migrate up and down intelligently.