Is there a way to automatically extract an existing Assets folder structure into a UPM package?

Let's presume that you have a project in which you want to extract a folder structure that adheres to the UPM conventions, and has Assembly Definitions. Let's presume it also contains prefabs that you already have in your scenes. Is there a way to automagically convert this folder structure into a UPM package?

Currently, when I try to extract such a folder manually and re-add it using the package manifest.json, the meta files don't match up correctly.

 

2018.4.11f1

The main problem is when your package contains MonoBehaviour or ScriptableObject code, and you have already assigned these scripts to objects either in a scene or to a Prefab, or have an existing ScriptableObject.

1. Create an empty Unity project
2. In the Assets folder, create a folder called UPMPackage.
3. In the UPMPackage folder, create a Runtime folder
4. In the Runtime folder, create a MonoBehaviour subclass named MyCode with any namespace you like.
5. In the Runtime folder, create your asmdef
6. In UPMPackage folder, create your package.json.
7. Add MyCode to a GameObject in your scene.

Observe: you have a game object with the desired script attached.

Next:

1. Export UPMPackage as a Unity package file
2. Create another new Unity project
3. Import your Unitypackage’s contents Into the new project. Verify that the code complies and is intact.

Next

1. In your original project, add the location of your package folder to manifest.json

Observe : your new package has conflicting guids and conflicting code definitions Unity makes new guids for the imported package.

Next

1. Delete the original UPMPackage folder from the first project
2. Click the GameObject to which you’d attached the original MyCode script

Observe : Missing MonoScript. This is because the GameObject is referencing the guid from the deleted version of the package.



This problem also happens if you delete the original package first and then later import the UPM package. Even though it doesn’t seem to need to generate new guids for the UPM package, there is still a mismatch.


This makes it impossible to externalize code that we would like to reuse, because we break all the gameobjects, prefabs, and ScriptableObjects that we’re created and depend on those original files with those original guids.

 

Note : I did manage to resolve that sample situation by re-re-importing the unitypackage file after adding the UPM package to the manifest. However, I’m uncertain if this is a viable solution for a larger project or a more complicated library.

This is why I feel like we need a tool that allows us to externalize an existing folder structure and ensures consistency of the guids inside the meta files, so that we don’t lose script references in the process.

 

don't do this.
instead:

1. setup your first project as before (code, asmdef, prefab etc...)
2. create an empty folder on disk, add a package.json and reference that in the manifest (Unity will see an empty package)
   • you can also create the folder inside Packages/ and you don't need to edit the manifest
3. from inside Unity, move the contents from Assets/ to Packages/your.package/
4. done

 

I’ll try that out later, as it does solve the immediate problem.

However, what that doesn’t do is give you a test project to ensure your package is complete and that you haven’t missed any hidden dependencies (eg: an asset store tool has littered the assets folder and you didn’t track down quite everything).

But your approach does sound promising, and I think I’ll try it out with some asset store packages.

 

after my steps, you can create a new empty project and add the package to the manifest.

the key part is that you never move asset files from outside unity (i.e. a single project), otherwise it can mess with the import

e.g. in your previous step, when you added the package from the new project to inside the main project, all of the assets are present twice in the project, with the same GUIDs. this will cause Unity to assign new GUIDs to those assets, breaking all the references.

if you need to do it (e.g. when updating an AS version of a package to it's newer, existing UPM version) you delete the assets first, then you add the package to the manifest. this way you don't have duplicate GUIDs at any given time, and Unity will not mess with them.
just remember to NOT save the project between those 2 steps, as Unity (or some custom inspector/editor code) can set missing references to null. restart Unity to be safer

 

Just wanted to report back : This works perfectly. Still wish Unity could create a tool to ease this process, but it's a start.