Unless I'm doing something wrong (my searches didn't turn anything up) msdeploy extensibility does not apply to the Powershell snap-in, or to the Visual Studio task library.
I understand that in VS.Net, the workaround is to set the property:
<PropertyGroup>
...
<UseMsdeployExe>true</UseMsdeployExe>
</PropertyGroup>
which instead invokes the command line. In powershell, it means you are also stuck using the command line which, while usable, means you cannot leverage powershell goodness. For instance, I can't call 'Restore-WDPackage' with a package that uses my custom providers.
My question is if this something the msdeploy dev team plan to address? (Or is there something I am not doing?)
Could I also suggest that for something to be 'extensible' it requires documentation? :o) The samples were a good start, but trivial (given sparse API docs) It is quite difficult to provide a custom provider, I ended up needing to use ILSpy to inspect the msdeploy .dll in order to figure out what the various methods were for and how they are used (and I would say my understanding is still vague) Once you get up and running, leveraging msdeploy is great! I love that I can simply write some code to slurp in config details, and some more code to perform configuration on destination and msdeploy handles all the serialization, packing, recursion and so on, and it appears in IIS manager! :)
-troy