How to do Slick configuration via application.conf from within custom sbt task? - scala

Question

I want to create an set task which creates a database schema with slick. For that, I have a task object like the following in my project:
object CreateSchema {
val instance = Database.forConfig("localDb")
def main(args: Array[String]) {
val createFuture = instance.run(createActions)
...
Await.ready(createFuture, Duration.Inf)
}
}
and in my build.sbt I define a task:
lazy val createSchema = taskKey[Unit]("CREATE database schema")
fullRunTask(createSchema, Runtime, "sbt.CreateSchema")
which gets executed as expected when I run sbt createSchema from the command line.
However, the problem is that application.conf doesn't seem to get taken into account (I've also tried different scopes like Compile or Test). As a result, the task fails due to com.typesafe.config.ConfigException$Missing: No configuration setting found for key 'localDb'.
How can I fix this so the configuration is available?
I found a lot of questions here that deal with using the application.conf inside the build.sbt itself, but that is not what I need.

Answer 1

I have setup a little demo using SBT 0.13.8 and Slick 3.0.0, which is working as expected. (And even without modifying "-Dconfig.resource".)
Files
./build.sbt
name := "SO_20150915"
version := "1.0"
scalaVersion := "2.11.7"
libraryDependencies ++= Seq(
"com.typesafe" % "config" % "1.3.0" withSources() withJavadoc(),
"com.typesafe.slick" %% "slick" % "3.0.0",
"org.slf4j" % "slf4j-nop" % "1.6.4",
"com.h2database" % "h2" % "1.3.175"
)
lazy val createSchema = taskKey[Unit]("CREATE database schema")
fullRunTask(createSchema, Runtime, "somefun.CallMe")
./project/build.properties
sbt.version = 0.13.8
./src/main/resources/reference.conf
hello {
world = "buuh."
}
h2mem1 = {
url = "jdbc:h2:mem:test1"
driver = org.h2.Driver
connectionPool = disabled
keepAliveConnection = true
}
./src/main/scala/somefun/CallMe.scala
package somefun
import com.typesafe.config.Config
import com.typesafe.config.ConfigFactory
import slick.driver.H2Driver.api._
/**
* SO_20150915
* Created by martin on 15.09.15.
*/
object CallMe {
def main(args: Array[String]) : Unit = {
println("Hello")
val settings = new Settings()
println(s"Settings read from hello.world: ${settings.hw}" )
val db = Database.forConfig("h2mem1")
try {
// ...
println("Do something with your database.")
} finally db.close
}
}
class Settings(val config: Config) {
// This verifies that the Config is sane and has our
// reference config. Importantly, we specify the "di3"
// path so we only validate settings that belong to this
// library. Otherwise, we might throw mistaken errors about
// settings we know nothing about.
config.checkValid(ConfigFactory.defaultReference(), "hello")
// This uses the standard default Config, if none is provided,
// which simplifies apps willing to use the defaults
def this() {
this(ConfigFactory.load())
}
val hw = config.getString("hello.world")
}
Result
If running sbt createSchema from Console I obtain the output
[info] Loading project definition from /home/.../SO_20150915/project
[info] Set current project to SO_20150915 (in build file:/home/.../SO_20150915/)
[info] Running somefun.CallMe
Hello
Settings read from hello.world: buuh.
Do something with your database.
[success] Total time: 1 s, completed 15.09.2015 10:42:20
Ideas
Please verify that this unmodified demo project also works for you.
Then try changing SBT version in the demo project and see if that changes something.
Alternatively, recheck your project setup and try to use a higher version of SBT.

Answer 2

Answer
So, even if your code resides in your src-folder, it is called from within SBT. That means, you are trying to load your application.conf from within the classpath context of SBT.
Slick uses Typesafe Config internally. (So the approach below (described in background) is not applicable, as you can not modify the Config loading mechanism itself).
Instead try the set the path to your application.conf explicitly via config.resource, see typesafe config docu (search for config.resource)
Option 1
Either set config.resource (via -Dconfig.resource=...) before starting sbt
Option 2
Or from within build.sbt as Scala code
sys.props("config.resource") = "./src/main/resources/application.conf"
Option 3
Or create a Task in SBT via
lazy val configPath = TaskKey[Unit]("configPath", "Set path for application.conf")
and add
configPath := Def.task {
sys.props("config.resource") = "./src/main/resources/application.conf"
}
to your sequence of settings.
Please let me know, if that worked.
Background information
Recently, I was writing a custom plugin for SBT, where I also tried to access a reference.conf as well. Unfortunately, I was not able to access any of .conf placed within project-subfolder using the default ClassLoader.
In the end I created a testenvironment.conf in project folder and used the following code to load the (typesafe) config:
def getConfig: Config = {
val classLoader = new java.net.URLClassLoader( Array( new File("./project/").toURI.toURL ) )
ConfigFactory.load(classLoader, "testenvironment")
}
or for loading a genereal application.conf from ./src/main/resources:
def getConfig: Config = {
val classLoader = new java.net.URLClassLoader( Array( new File("./src/main/resources/").toURI.toURL ) )
// no .conf basename given, so look for reference.conf and application.conf
// use specific classLoader
ConfigFactory.load(classLoader)
}