BuildUtilities.RegisterShouldIncludeInBuildCallback unclear

Dear Community,

PackageManager Api docs specify 2 options to include or exclude package content from a Project / Build.

BuildUtilities.RegisterShouldIncludeInBuildCallback https://docs.unity3d.com/ScriptRefe...ies.RegisterShouldIncludeInBuildCallback.html
IShouldIncludeInBuildCallback https://docs.unity3d.com/ScriptReference/PackageManager.IShouldIncludeInBuildCallback.html

I wanted to see if this is allowing us to include or exclude packages from a Build based on some custom configurations we create. Thats at least what I expected is possible reading the documentation.
Now all my tries to get this configuration somehow going are miserably failing. The ShouldIncludeInBuild Method is never invoked.

Here is a quick and ugly implementation that should register an instance of PackageManagerBuildConfiguration per package and should be invoked at some point of project or build creation.

Now Listing of Packages works.
PackageName getter is called 3 times per package.
ShouldIncludeInBuild is never invoked. Any ideas?

We do have a project that is configured and compiled slightly different to multiple platforms.
So we would for example love to add the AR Foundation package in one case, but not the other.
With assemblys and scripting define symbol restriction for assemblies we can handle our code and inclusion pretty well.
But what is the way to go with the package manager?
How do we include / exclude packages by scripting or by scripting define symbols?

Any help appreciated, thank you.

Code (CSharp):

1. using UnityEngine;
2. using UnityEditor;
3. using UnityEditor.PackageManager;
4.  
5. public class PackageManagerBuildConfiguration : IShouldIncludeInBuildCallback
6. {
7.     private static UnityEditor.PackageManager.Requests.ListRequest request;
8.  
9.     [MenuItem("Tools/PackageManager/HookIntoBuild")][InitializeOnLoadMethod]
10.     public static void HoockIntoPackageManager()
11.     {
12.         Debug.Log("PackageManagerBuildConfiguration -- Scripting Environment launched");
13.  
14.         request = Client.List(false);
15.  
16.         EditorApplication.update += Update;
17.     }
18.  
19.     static void Update()
20.     {
21.         if (request == null)
22.             return;
23.  
24.  
25.         if(request.IsCompleted)
26.         {
27.             using (System.IO.StringWriter writer = new System.IO.StringWriter())
28.             {
29.                 foreach (UnityEditor.PackageManager.PackageInfo r in request.Result)
30.                 {
31.                     writer.WriteLine(string.Format(
32.                         "packageId: {0}, " +
33.                         "status: {1}, " +
34.                         "version: {2}, " +
35.                         "assetPath: {3}, " +
36.                         "author_ {4}, " +
37.                         "category: {5}, " +
38.                         "description: {6}, " +
39.                         "name: {7}",
40.                         r.packageId,
41.                         r.status,
42.                         r.assetPath,
43.                         r.author,
44.                         r.category,
45.                         r.description,
46.                         r.version,
47.                         r.name));
48.  
49.  
50.                     writer.WriteLine("\n");
51.  
52.                     BuildUtilities.RegisterShouldIncludeInBuildCallback(new PackageManagerBuildConfiguration(r.name));
53.                 }
54.  
55.                 Debug.Log(writer);
56.             }
57.  
58.             request = null;
59.             EditorApplication.update -= Update;
60.         }
61.     }
62.  
63.     public string PackageName
64.     {
65.         get
66.         {
67.  
68.             Debug.Log(_packageName);
69.  
70.             return _packageName;
71.         }
72.     }
73.  
74.     private string _packageName;
75.  
76.     public PackageManagerBuildConfiguration(string packageName)
77.     {
78.         _packageName = packageName;
79.     }
80.  
81.     public bool ShouldIncludeInBuild(string path)
82.     {
83.         Debug.Log("ShouldIncludeInBuild: " + path);
84.  
85.         return false;
86.     }
87. }

 

Thank you for clarifying this with the *.dll
I actually expected it to be triggered at Build time, but didn't get anything since I didn't have any dll packages included, so I was not sure anymore.

Thing with not linked packages is, that C# is stripped is true, except for native plugins.
Native Plugins are also exported even if the C# wrapper linking it is not referenced. So using ARFoundation in our case would bring stuff from ARKit and ARCore along with it. Bloating our non AR version of the App.

Question to adding and removing packages is then, How do I know which packages are imported or not?
In the List Request I only see the status : Available, but there is no imported/included whatsoever state indicating that a package is included in the Project.
Do I just trigger a best guess add or remove and if its included it wont be added again, or removal would fail?

PS:
For Recompilation, I'm already past this barrier, I'm writing a lockflag to tmp/ then changing ScriptingDefineSymbols and other PlayerSettings that come with a recompile. Then recover at [InitializeOnLoadAttribute] from the lockflag. So package changes is a doable.