Package Manager packages support references to outside project

I was surprised to find out that it is possible to have a package managed by Package Manager with references to the game project.

I was moving some files from one project into a package to be used in a new project, using the Package Manager. I was following https://docs.unity3d.com/Manual/CustomPackages.html

Some of these files have references to a plugin, so I had the idea to #ifdef the lines that use the plugin so if in the future someone decides to use the same plugin they can add a compilation directive to enable the code in the package. But then I thought it wouldn't work, because:

1. maybe compilation directives from Player Preferences are not used when compiling packages;
2. maybe packages are compiled before everyone else;
3. the package has its own asmdef which doesn't point to the plugin.

But it did work!

Something doesn't look right here. What is happening?




Example
In my package I have a .cs file with the following:

Code (CSharp):

1. #if USE_ODIN_INSPECTOR
2. using Sirenix.OdinInspector;
3. #endif

If I add the package using the Package Manager, set USE_ODIN_INSPECTOR in PlayerPreferences and add the plugin to my project everything works fine.

This is probably the first post where someone is complaining because something is working.

 

I assume this works because you made your package expect to reference the plugin in the project. This wouldn't otherwise work if those scripts were loosely contained in the project space.