Uninstalled add-ins aren't properly removed

[cameronwhite]

After an add-in is uninstalled, e.g. the Night Vision add-in, on the next launch the add-in is still registered even though some files are missing:

Pinta: Failed to initialize add-in
System.IO.FileNotFoundException: Could not load file or assembly 'NightVisionAddin, Version=1.3.1.0, Culture=neutral, PublicKeyToken=null'. The system cannot find the file specified.

File name: 'NightVisionAddin, Version=1.3.1.0, Culture=neutral, PublicKeyToken=null'
 ---> System.IO.FileNotFoundException: Could not load file or assembly '/Users/cameron/Library/Application Support/Pinta/addins/addins/NightVisionEffect.1.3.2/NightVisionAddin.dll'. The system cannot find the file specified.

File name: '/Users/cameron/Library/Application Support/Pinta/addins/addins/NightVisionEffect.1.3.2/NightVisionAddin.dll'
   at System.Runtime.Loader.AssemblyLoadContext.LoadFromAssemblyPath(String assemblyPath)
   at System.Reflection.Assembly.LoadFrom(String assemblyFile)
   at Mono.Addins.AddinEngine.CurrentDomainAssemblyResolve(Object sender, ResolveEventArgs args) in /Users/cameron/code/mono-addins/Mono.Addins/Mono.Addins/AddinEngine.cs:line 324
   at System.Runtime.Loader.AssemblyLoadContext.InvokeResolveEvent(ResolveEventHandler eventHandler, RuntimeAssembly assembly, String name)
   at System.Reflection.RuntimeAssembly.InternalLoad(AssemblyName assemblyName, StackCrawlMark& stackMark, AssemblyLoadContext assemblyLoadContext, RuntimeAssembly requestingAssembly, Boolean throwOnFileNotFound)
   at System.Reflection.TypeNameParser.ResolveAssembly(String assemblyName)
   at System.Reflection.TypeNameParser.GetType(String typeName, ReadOnlySpan`1 nestedTypeNames, String assemblyNameIfAny)
   at System.Reflection.TypeNameParser.Parse()
   at System.Reflection.TypeNameParser.GetType(String typeName, Func`2 assemblyResolver, Func`4 typeResolver, Assembly requestingAssembly, Boolean throwOnError, Boolean ignoreCase, Boolean extensibleParser)
   at System.Type.GetType(String typeName, Boolean throwOnError)
   at Mono.Addins.RuntimeAddin.GetType(String typeName, Boolean throwIfNotFound) in /Users/cameron/code/mono-addins/Mono.Addins/Mono.Addins/RuntimeAddin.cs:line 338
   at Mono.Addins.TypeExtensionNode.get_Type() in /Users/cameron/code/mono-addins/Mono.Addins/Mono.Addins/TypeExtensionNode.cs:line 104
   at Mono.Addins.TypeExtensionNode.CreateInstance() in /Users/cameron/code/mono-addins/Mono.Addins/Mono.Addins/TypeExtensionNode.cs:line 93
   at Mono.Addins.InstanceExtensionNode.GetInstance() in /Users/cameron/code/mono-addins/Mono.Addins/Mono.Addins/InstanceExtensionNode.cs:line 76
   at Mono.Addins.ExtensionNodeEventArgs.get_ExtensionObject() in /Users/cameron/code/mono-addins/Mono.Addins/Mono.Addins/ExtensionContext.cs:line 1331
   at Pinta.MainWindow.OnExtensionChanged(Object s, ExtensionNodeEventArgs args) in /Users/cameron/code/Pinta/Pinta/MainWindow.cs:line 273

[cameronwhite]

From my investigation there are a couple issues here:

• The satellite assemblies from translations are automatically packaged by mautil but aren't listed as file dependencies of the add-in. The uninstall action leaves these files behind, which causes it to fail to remove the add-in directory. The add-in file scanning then thinks an add-in is present since the folders still exist
• The add-in removal also doesn't go through the normal process if the assemblies are loaded - in this case the add-in files are flagged for removal on the next run. This code path only removes the files and doesn't clear out the add-in folder, also causing the same issue with the add-in not being removed properly. This is somewhat related to RunPendingUninstalls not cleaning up empty directories mono/mono-addins#56

[cameronwhite]

The first issue should be fixable by explicitly listing the satellite assemblies in the add-in manifest, but the second issue may require forking Mono.Addins, since the upstream repository now seems to be archived / read-only ...