How to set system properties for runMain on command line? - sbt

Question

How can I set a system property for runMain upon executing it from command line on Windows?
I'd like to be able to run the following command:
sbt -Dconfig.resource=../application.conf "runMain akka.Main com.my.main.Actor"
Regardless of whether fork is true, whether I put it in SBT_OPTS, or how I pass it in I cannot accomplish this. I am familiar with both Setting value of setting on command line when no default value defined in build? and Setting system properties with "sbt run" but neither answer my question.
Other questions seem to indicate you can't even easily view the Java invocation arguments easily in SBT. Any help is appreciated.

Answer 1

This works:
sbt '; set javaOptions += "-Dconfig.resource=../application.conf" ; runMain akka.Main com.my.main.Actor'
If this isn't a "friendly" enough syntax, wrap it in a little shell script.
(Note this assumes you have fork set to true for running. If you don't, see akauppi's comment.)

Answer 2

You could use envVars setting. I'm unsure how idiomatic it is in SBT, though.
> help envVars
Environment variables used when forking a new JVM
The following (very minimalistic) build.sbt worked fine.
fork := true
envVars := Map("msg" -> "hello")
Once you get it running, setting envVars to any value with set does the trick.
> help set
set [every] <setting-expression>
Applies the given setting to the current project:
1) Constructs the expression provided as an argument by compiling and loading it.
2) Appends the new setting to the current project's settings.
3) Re-evaluates the build's settings.
This command does not rebuild the build definitions, plugins, or configurations.
It does not automatically persist the setting(s) either.
To persist the setting(s), run 'session save' or 'session save-all'.
If 'every' is specified, the setting is evaluated in the current context
and the resulting value is used in every scope. This overrides the value
bound to the key everywhere.
I've got a simple app to run.
$ sbt run
[info] Set current project to fork-testing (in build file:/C:/dev/sandbox/fork-testing/)
[info] Running Hello
[info] hello
With the envVars setting changed on the command line the output would change as follows:
$ sbt 'set envVars := Map("msg" -> "Hello, Chad")' run
[info] Set current project to fork-testing (in build file:/C:/dev/sandbox/fork-testing/)
[info] Defining *:envVars
[info] The new value will be used by *:runner, compile:run::runner and 1 others.
[info] Run `last` for details.
[info] Reapplying settings...
[info] Set current project to fork-testing (in build file:/C:/dev/sandbox/fork-testing/)
[info] Running Hello
[info] Hello, Chad
runMain is no different from run in this case.
$ sbt 'set envVars := Map("msg" -> "Hello, Chad")' 'runMain Hello'
[info] Set current project to fork-testing (in build file:/C:/dev/sandbox/fork-testing/)
[info] Defining *:envVars
[info] The new value will be used by *:runner, compile:run::runner and 1 others.
[info] Run `last` for details.
[info] Reapplying settings...
[info] Set current project to fork-testing (in build file:/C:/dev/sandbox/fork-testing/)
[info] Running Hello
[info] Hello, Chad

Answer 3

If you're trying to set SBT properties, like plugin settings, then the above won't work (AFAICT) as of 0.13+ in my experience. The following however did work, when trying to pass in Liquibase settings, like password, from our CI frameworks.
In your build.sbt
Ugly, but supplies defaults, and optionally grabs from System.properties. This way you've got your default and override cases covered.
def sysPropOrDefault(propName:String,default:String):String = Option(System.getProperty(propName)).getOrElse(default)
liquibaseUsername := sysPropOrDefault("liquibase.username","change_me")
liquibasePassword := sysPropOrDefault("liquibase.password","chuck(\)orris")
From the commandline
Now just override via -Dprop=value like you would with Maven or other JVM programs. Note props appear before SBT task.
sbt -Dliquibase.password="shh" -Dliquibase.username="bob" liquibase:liquibase-update