Can't activate packrat if not in the packrat project

packrat::on() has a project argument that should allow to activate a project from another working directory. My use case to find this error is using packrat with docker and shiny server.

When I am in let's say the user home and I want to activate packrat with packrat::on() after unbundling, I run

Rscript -e "packrat::on('/srv/shiny-server/app_folder')" 

I get this error message

Error in read.dcf(...) : cannot open the connection
Calls: <Anonymous> ... getPackageDependencies -> readLockFilePackages -> readDcf -> read.dcf
In addition: Warning message:
In read.dcf(...) :
  cannot open compressed file '//packrat/packrat.lock', probable reason 'No such file or directory'
Execution halted

This is because somewhere getPackageDependencies is called without any project argument and readLockFilePackages(file = lockFilePath()) is run searching for packrat.lock in the current working directory.

Before investigating further, is this an intended use of the project argument from packrat::on ?

Thanks.

Start with packrat::on and trace how its project argument reaches getPackageDependencies, readLockFilePackages, readDcf, and lockFilePath. Reproduce the Rscript command from another working directory and inspect how packrat.lock is resolved. Done means activating the target project uses its lock file instead of searching the current directory.