Debugging database deployments with MSDeploy and SqlPackage

I recently had problems deploying a database to Azure, and thanks to this article, I now know why. The best part of this experience is that I've learned to debug this in a much easier manner than relying on the unhelpful error message:

*** An error occurred during deployment plan generation. Deployment cannot continue.
Failed to import target model my-database-name. Detailed message Value cannot be null.
Parameter name: conn
Value cannot be null.
Parameter name: conn

The short of it is that:

1) you need to enable a log trace with these commands for dbDacFx and SSDT:

logman create trace -n DacFxDebug -p "Microsoft-SQLServerDataTools" 0x800 -o "%LOCALAPPDATA%\DacFxDebug.etl" -ets

logman create trace -n SSDTDebug -p "Microsoft-SQLServerDataToolsVS" 0x800 -o "%LOCALAPPDATA%\SSDTDebug.etl" -ets

2) Go execute the command that's causing you grief
3) Execute the following commands to stop the logging trace:

logman stop DacFxDebug -ets

logman stop SSDTDebug -ets

4) Open 'eventvwr' in the Run dialog available from the Start Menu
5) Go to the right side 'Actions' pane, and click on 'Open Saved Log'.
6) When prompted to convert the log, click 'No'.

The logs will display under the 'Saved Logs' folder in the left hand navigation tree, and you'll be able to inspect the errors that occurred. Good luck with deployment!