Improve plugin directory structure to handle multiple different versions of a package

[yacchin1205]

To resolve Issue #3, I propose to improve the structure of the plugin_packages directory and implement a manager to manage it. (I use live-plugin-manager for etherpad-lite and it would be great to improve it! https://github.com/ether/etherpad-lite/issues/6330 )

Directory structure

Currently, the file placement would look like the following.

• plugin_packages/
  • (plugin_name)/

Therefore, I understand that if plugin-b and plugin-c each depend on a different version of plugin-a, one of the versions will be overwritten.

• plugin_packages/
  • plugin-a/
  • plugin-b/
  • plugin-c/

So, I considered creating a node_modules in the dependent source directory, like https://stackoverflow.com/questions/42147243/how-does-npm-handle-version-conflicts, and placing the dependencies packages in it.

• plugin_packages/
  • (plugin_name) -symlink-> ./.versions/(plugin_name)@(plugin_version)
  • .versions/
  • (plugin_name)@(plugin_version)
    • node_modules
    • (dep_plugin_name) -symlink->(dep_plugin_name)@(dep_plugin_version)

To prevent multiple copies of the same package, symlink is used. The example of plugin-b and plugin-c is shown below.

• plugin_packges/
  • plugin-a -> .versions/plugin-a@v2.0.0
  • plugin-b -> .versions/plugin-b@v1.0.0
  • plugin-c -> .versions/plugin-c@v1.0.0
  • .versions/
  • plugin-a@v1.0.0/
  • plugin-a@v2.0.0/
  • plugin-b@v1.0.0/
    • node_modules
    • plugin-a -> plugin-a@v1.0.0
  • plugin-c@v1.0.0/
    • node_modules
    • plugin-a -> plugin-a@v2.0.0

For compatibility with current behavior, a symlink also will be created under plugin_packages for plugin-a, which is a dependency of plugin-b or plugin-c. Which version is linked depends on whether plugin-b or plugin-c is installed later.

Changes to code

The following changes were made to achieve the directory placement.

• Added VersionManager to manage packages in the .versions directory
• Modified PluginManager to ask VersionManager to determine package location and management
• Modified PluginVm to allow plugins to resolve their own local dependencies
• Modified and added tests

[davideicardi]

Thank you @yacchin1205 ! This is a great improvement! :rocket: Give me some time to review it, but I will try to do that in a couple of days.

[davideicardi]

Thank you again @yacchin1205 ! 👏

[yacchin1205]

Thanks for your review and merge, too! 😄

[davideicardi]

I will publish a new release soon (just waiting for another PR rebase).