Clone the source code from the git repo.
In the VSCode:
- "File"=>"Preferences"=>"Settings" =>"Node Debug"=>"Auto Attach=On"
- "File"=>"Preferences"=>"Settings" =>"Node Debug"=>"Use Preview Auto Attach=Off"
Set necessary break points in the .ts files of the project.
To start debugging the source code just add --dev-suspend flag to each CLI command that runs the SFDMU Plugin.
Starting from the latest node.js versions the --dev-suspend flag might stop to work. In this case you have the alternative way to start debugging. Run the sfdx:run command as following (without sfdx sfdmu:run): ./debug.cmd --sourceusername firstname.lastname@example.org --targetusername email@example.com -- other sfdmu flags...
This command will start a debug session.
Note, that if you are working with MacOS, you probably will need first to update the access rights to the file debug.cmd by running the command: chmod 777 ./debug.cmd