MSbuild of VS solution under target clean is just plain wrong

One of our solutions has been bothering us for a long time so I finally decided to make a simple demo of the problem.

In my demo solution I have three library type C# projects Level0, Level1 and Level2. Adding and removing a (project) reference from Level1 to Level0 and building with both default and clean targets using MSBuild illustrates the problem. Beneath is the ouput of the clean build without the reference in place:

C:\Test\BuildDependencies>msbuild C:\Test\BuildDependencies\BuildDependencies.sln /t:clean
Microsoft (R) Build Engine Version 3.5.30729.1[Microsoft .NET Framework, Version 2.0.50727.3053]Copyright (C) Microsoft Corporation 2007. All rights reserved.
Build started 12/29/2008 4:01:39 PM.Project "C:\Test\BuildDependencies\BuildDependencies.sln" on node 0 (clean target(s)). Building solution configuration "DebugAny CPU".Project "C:\Test\BuildDependencies\BuildDependencies.sln" (1) is building "C:\Test\BuildDependencies\Level0\Level0.csproj" (2) on node 0 (Clean target(s)). Deleting file "C:\Test\BuildDependencies\Level0\bin\Debug\Level0.dll". Deleting file "C:\Test\BuildDependencies\Level0\bin\Debug\Level0.pdb". Deleting file "C:\Test\BuildDependencies\Level0\obj\Debug\Level0.dll". Deleting file "C:\Test\BuildDependencies\Level0\obj\Debug\Level0.pdb".EntityClean: Successfully cleaned the output for 0 EDMX files.Done Building Project "C:\Test\BuildDependencies\Level0\Level0.csproj" (Clean target(s)).
Project "C:\Test\BuildDependencies\BuildDependencies.sln" (1) is building "C:\Test\BuildDependencies\Level1\Level1.csproj" (3) on node 0 (Clean target(s)). Deleting file "C:\Test\BuildDependencies\Level1\bin\Debug\Level1.dll". Deleting file "C:\Test\BuildDependencies\Level1\bin\Debug\Level1.pdb". Deleting file "C:\Test\BuildDependencies\Level1\bin\Debug\Level1.tlb". Deleting file "C:\Test\BuildDependencies\Level1\obj\Debug\Level1.dll". Deleting file "C:\Test\BuildDependencies\Level1\obj\Debug\Level1.pdb".EntityClean: Successfully cleaned the output for 0 EDMX files.Done Building Project "C:\Test\BuildDependencies\Level1\Level1.csproj" (Clean target(s)).
Project "C:\Test\BuildDependencies\BuildDependencies.sln" (1) is building "C:\Test\BuildDependencies\Level2\Level2.csproj" (4) on node 0 (Clean target(s)). Deleting file "C:\Test\BuildDependencies\Level2\bin\Debug\Level2.dll". Deleting file "C:\Test\BuildDependencies\Level2\bin\Debug\Level2.pdb". Deleting file "C:\Test\BuildDependencies\Level2\obj\Debug\Level2.dll". Deleting file "C:\Test\BuildDependencies\Level2\obj\Debug\Level2.pdb".EntityClean: Successfully cleaned the output for 0 EDMX files.Done Building Project "C:\Test\BuildDependencies\Level2\Level2.csproj" (Clean target(s)).
Done Building Project "C:\Test\BuildDependencies\BuildDependencies.sln" (clean target(s)).
Build succeeded. 0 Warning(s) 0 Error(s)

Here is the output with the reference (Level1 -> Level0) in place:

C:\Test\BuildDependencies>msbuild C:\Test\BuildDependencies\BuildDependencies.sln /t:clean
Microsoft (R) Build Engine Version 3.5.30729.1[Microsoft .NET Framework, Version 2.0.50727.3053]Copyright (C) Microsoft Corporation 2007. All rights reserved.
Build started 12/29/2008 4:02:14 PM.Project "C:\Test\BuildDependencies\BuildDependencies.sln" on node 0 (clean target(s)). Building solution configuration "DebugAny CPU".Project "C:\Test\BuildDependencies\BuildDependencies.sln" (1) is building "C:\Test\BuildDependencies\Level0\Level0.csproj" (2) on node 0 (Clean target(s)). Deleting file "C:\Test\BuildDependencies\Level0\bin\Debug\Level0.dll". Deleting file "C:\Test\BuildDependencies\Level0\bin\Debug\Level0.pdb". Deleting file "C:\Test\BuildDependencies\Level0\obj\Debug\Level0.dll". Deleting file "C:\Test\BuildDependencies\Level0\obj\Debug\Level0.pdb".EntityClean: Successfully cleaned the output for 0 EDMX files.Done Building Project "C:\Test\BuildDependencies\Level0\Level0.csproj" (Clean target(s)).
Project "C:\Test\BuildDependencies\BuildDependencies.sln" (1) is building "C:\Test\BuildDependencies\Level2\Level2.csproj" (3) on node 0 (Clean target(s)). Deleting file "C:\Test\BuildDependencies\Level2\bin\Debug\Level2.dll". Deleting file "C:\Test\BuildDependencies\Level2\bin\Debug\Level2.pdb". Deleting file "C:\Test\BuildDependencies\Level2\obj\Debug\Level2.dll". Deleting file "C:\Test\BuildDependencies\Level2\obj\Debug\Level2.pdb".EntityClean: Successfully cleaned the output for 0 EDMX files.Done Building Project "C:\Test\BuildDependencies\Level2\Level2.csproj" (Clean target(s)).
Project "C:\Test\BuildDependencies\BuildDependencies.sln" (1) is building "C:\Test\BuildDependencies\Level1\Level1.csproj" (4) on node 0 (Clean target(s)). Deleting file "C:\Test\BuildDependencies\Level1\bin\Debug\Level1.dll". Deleting file "C:\Test\BuildDependencies\Level1\bin\Debug\Level1.pdb". Deleting file "C:\Test\BuildDependencies\Level1\bin\Debug\Level1.tlb". Deleting file "C:\Test\BuildDependencies\Level1\bin\Debug\Level0.dll". Deleting file "C:\Test\BuildDependencies\Level1\bin\Debug\Level0.pdb". Deleting file "C:\Test\BuildDependencies\Level1\obj\Debug\ResolveAssemblyReference.cache". Deleting file "C:\Test\BuildDependencies\Level1\obj\Debug\Level1.dll". Deleting file "C:\Test\BuildDependencies\Level1\obj\Debug\Level1.pdb".EntityClean: Successfully cleaned the output for 0 EDMX files.Done Building Project "C:\Test\BuildDependencies\Level1\Level1.csproj" (Clean target(s)).
Done Building Project "C:\Test\BuildDependencies\BuildDependencies.sln" (clean target(s)).

Now, the point is that allthough adding the reference alters the build order MSBuild does not build the clean targets in the correct order.

If you don't beleive me have a look at the .sln.cache that gets generated (if you use MSBuild V3 and VS2008). Compare the Clean and the Build targets and you will see that the build order is the same (BuildLevel0 is done before BuildLevel1 etc.).

Cleaning a referer after the referee (is that the right term?) will fail in some cases. Specifically it will fail if you need the refered assembly to clean the current assembly.

When do you need the referred assembly to clean the current one? Well our build breaks during clean with the "MSB3395: Cannot unregister assembly" error. It seems our referring assembly needs some type in the referred assembly to properly unregister. I am currently investigating why this is the case but the result doesn't change the fact that MSBuild has an issue here.

It's obvious if you think about it. If you have access to dependency information you should always clean in the opposite order of the way you normally build. Am I the only one getting this?!? Shouldn't this be obvious to the guys in redmond too?!?