Multiple SBT Configurations should be exclusive, but they all activate at the same time - why? - scala

Question

I have defined a minimal build.sbt with two custom profiles ‘dev’ and ‘staging’ (what SBT seems to call Configurations). However, when I run SBT with the Configuration that was defined first in the file (dev), both Configuration blocks are executed - and if both modify the same setting, the last one wins (staging).
This seems to break any notion of conditional activation, so what am I doing wrong with SBT?
For reference, I want to emulate the conditionally activated Profiles concept of Maven e.g. mvn test -P staging.
SBT version: 1.2.1
build.sbt:
name := "example-project"
scalaVersion := "2.12.6"
...
fork := true
// Environment-independent JVM property (always works)
javaOptions += "-Da=b"
// Environment-specific JVM property (doesn’t work)
lazy val Dev = config("dev") extend Test
lazy val Staging = config("staging") extend Test
val root = (project in file("."))
.configs(Dev, Staging)
.settings(inConfig(Dev)(Seq(javaOptions in Test += "-Dfoo=bar")))
.settings(inConfig(Staging)(Seq(javaOptions in Test += "-Dfoo=qux")))
Command:
# Bad
sbt test
=> foo=qux
a=b
# Bad
sbt clean dev:test
=> foo=qux
a=b
# Good
sbt clean staging:test
=> foo=qux
a=b

Answer 1

Notice that despite of the inConfig usage you're still setting javaOptions in Test, i.e. in the Test config. If you remove in Test, it works as expected:
...
.settings(inConfig(Dev)(javaOptions += "-Dfoo=bar"))
.settings(inConfig(Staging)(javaOptions += "-Dfoo=qux"))
(also Seq(...) wrapping is unnecessary)
Now in sbt:
> show Test/javaOptions
[info] *
> show Dev/javaOptions
[info] * -Dfoo=bar
> show Staging/javaOptions
[info] * -Dfoo=qux
You can achieve the same result by scoping each setting explicitly (without inConfig wrapping):
.settings(
Dev/javaOptions += "-Dfoo=bar",
Staging/javaOptions += "-Dfoo=qux",
...
)
(here Conf/javaOptions is the same as javaOptions in Conf)