Scala changing parquet path in config (typesafe)

Currently I have a configuration file like this:

project {
  inputs {
    baseFile {
      paths = ["project/src/test/resources/inputs/parquet1/date=2020-11-01/"]
      type = parquet
      applyConversions = false
    }
  }
}

And I want to change the date "2020-11-01" to another one during run time. I read I need a new config object since it's immutable, I'm trying this but I'm not quite sure how to edit paths since it's a list and not a String and it definitely needs to be a list or else it's going to say I haven't configured a path for the parquet.

val newConfig = config.withValue("project.inputs.baseFile.paths"(0),
        ConfigValueFactory.fromAnyRef("project/src/test/resources/inputs/parquet1/date=2020-10-01/"))

But I'm getting a:

Error com.typesafe.config.ConfigException$BadPath: path parameter: Invalid path 'project.inputs.baseFile.': path has a leading, trailing, or two adjacent period '.' (use quoted "" empty string if you want an empty element)

What's the correct way to set the new path?

Solution

One option you have, is to override the entire array:

import scala.collection.JavaConverters._
val mergedConfig = config.withValue("project.inputs.baseFile.paths",
                      ConfigValueFactory.fromAnyRef(Seq("project/src/test/resources/inputs/parquet1/date=2020-10-01/").asJava))

But a more elegant way to do this (IMHO), is to create a new config, and to use the existing as a fallback.

For example, we can create a new config:

val newJsonString = """project {
                   |inputs {
                   |baseFile {
                   |  paths = ["project/src/test/resources/inputs/parquet1/date=2020-10-01/"]
                   |}}}""".stripMargin

val newConfig = ConfigFactory.parseString(newJsonString)

And now to merge them:

val mergedConfig = newConfig.withFallback(config)

The output of:

println(mergedConfig.getList("project.inputs.baseFile.paths"))
println(mergedConfig.getString("project.inputs.baseFile.type"))

is:

SimpleConfigList(["project/src/test/resources/inputs/parquet1/date=2020-10-01/"])
parquet

As expected.

You can read more about Merging config trees. Code run at Scastie.

I didn't find any way to replace one element of the array with withValue.