*Reproducible on:*
* VS version: 1.7.6
* Unity version: 2021.2.2f1

*Case 1:*
*Note:* This bug came from the forum: https://forum.unity.com/threads/additional-editor-assemblies-are-not-detected-correctly.1197328/

If my editor assembly (created using an assembly definition) is not one of the special names Assembly-CSharp-Editor or Assembly-CSharp-Editor-firstpass, I have to have an [assembly: AssemblyIsEditorAssembly] somewhere in it. But when I do that, watch what happens in the function above: _editorAssemblyCache.TryGetValue returns false and sets isEditor to default (false), then Attribute.IsDefined returns true, and a key value pair of (assembly, false) is added to _editorAssemblyCache. Thereafter, _editorAssemblyCache keeps serving the wrong false value.

* Consider this function in Codebase.cs (package version 1.7.6):
{code:java}
Code (CSharp):
private static bool IsEditorAssembly(Assembly assembly)
{
// assembly.GetName() is surprisingly expensive, keep a cache
if (_editorAssemblyCache.TryGetValue(assembly, out var isEditor))
return isEditor;
if (Attribute.IsDefined(assembly, typeof(AssemblyIsEditorAssembly)))
{
_editorAssemblyCache.Add(assembly, isEditor); // <== isEditor is always false!
return true;
}

var isEditorAssembly = IsEditorAssembly(assembly.GetName());
_editorAssemblyCache.Add(assembly, isEditorAssembly);
return isEditorAssembly;
}
{code}

* Workaround from the user: make sure your editor assembly uses something from UnityEditor.CoreModule, for example:

{code:java}
Code (CSharp):
internal class DummyEditorDependency : UnityEditor.Editor { }
{code}

*Case 2:*

Small bug in Codebase.IsEditorAssembly() (1.7.5, also 1.7.6): l.330 _editorAssemblyCache.Add(assembly, isEditor); should be _editorAssemblyCache.Add(assembly, true); At the moment it's not possible to add visual scripting editor extensions in separate Assemblies because of this. (edited)