Substituting environment variables fails when merging objects

[yantonov]

From the first glance it's related to https://github.com/lightbend/config/issues/356 https://github.com/lightbend/config/issues/647 https://github.com/lightbend/config/issues/725

Here is an example of the config:

prod {
    catalog {
        aws-access-key-id = [ "1" ]
        aws-access-list-key-id = [ "1" ]
    }
}

dev = ${prod} {
    catalog {
        # doesn't work
        aws-access-key-id = "2"
        aws-access-key-id = ${?AWS_ACCESS_KEY_ID}
        # but this one works
        aws-access-list-key-id = [ "2", ${?AWS_ACCESS_KEY_ID} ]
    }
}

Error:

Stack:

com.typesafe.config.ConfigException$BugOrBroken: SimpleConfigObject.replaceChild did not find SimpleConfigObjec
    at com.typesafe.config.impl.SimpleConfigObject.replaceChild(SimpleConfigObject.java:216)
    at com.typesafe.config.impl.SimpleConfigObject.replaceChild(SimpleConfigObject.java:26)
    at com.typesafe.config.impl.ResolveSource.replace(ResolveSource.java:192)
    at com.typesafe.config.impl.ResolveSource.replace(ResolveSource.java:193)
    at com.typesafe.config.impl.ResolveSource.replaceCurrentParent(ResolveSource.java:209)
    at com.typesafe.config.impl.ResolveSource.replaceWithinCurrentParent(ResolveSource.java:240)
    at com.typesafe.config.impl.ConfigDelayedMerge.resolveSubstitutions(ConfigDelayedMerge.java:110)
    at com.typesafe.config.impl.ConfigDelayedMerge.resolveSubstitutions(ConfigDelayedMerge.java:59)
    at com.typesafe.config.impl.ResolveContext.realResolve(ResolveContext.java:183)
    at com.typesafe.config.impl.ResolveContext.resolve(ResolveContext.java:146)
    at com.typesafe.config.impl.SimpleConfigObject$ResolveModifier.modifyChildMayThrow(SimpleConfigObject.java:380)
    at com.typesafe.config.impl.SimpleConfigObject.modifyMayThrow(SimpleConfigObject.java:313)
    at com.typesafe.config.impl.SimpleConfigObject.resolveSubstitutions(SimpleConfigObject.java:399)
    at com.typesafe.config.impl.ResolveContext.realResolve(ResolveContext.java:183)
    at com.typesafe.config.impl.ResolveContext.resolve(ResolveContext.java:146)
    at com.typesafe.config.impl.SimpleConfigObject$ResolveModifier.modifyChildMayThrow(SimpleConfigObject.java:380)
    at com.typesafe.config.impl.SimpleConfigObject.modifyMayThrow(SimpleConfigObject.java:313)
    at com.typesafe.config.impl.SimpleConfigObject.resolveSubstitutions(SimpleConfigObject.java:399)
    at com.typesafe.config.impl.ResolveContext.realResolve(ResolveContext.java:183)
    at com.typesafe.config.impl.ResolveContext.resolve(ResolveContext.java:146)
    at com.typesafe.config.impl.ConfigConcatenation.resolveSubstitutions(ConfigConcatenation.java:205)
    at com.typesafe.config.impl.ResolveContext.realResolve(ResolveContext.java:183)
    at com.typesafe.config.impl.ResolveContext.resolve(ResolveContext.java:146)
    at com.typesafe.config.impl.SimpleConfigObject$ResolveModifier.modifyChildMayThrow(SimpleConfigObject.java:380)
    at com.typesafe.config.impl.SimpleConfigObject.modifyMayThrow(SimpleConfigObject.java:313)
    at com.typesafe.config.impl.SimpleConfigObject.resolveSubstitutions(SimpleConfigObject.java:399)
    at com.typesafe.config.impl.ResolveContext.realResolve(ResolveContext.java:183)
    at com.typesafe.config.impl.ResolveContext.resolve(ResolveContext.java:146)
    at com.typesafe.config.impl.ResolveContext.resolve(ResolveContext.java:235)
    at com.typesafe.config.impl.SimpleConfig.resolveWith(SimpleConfig.java:79)
    at com.typesafe.config.impl.SimpleConfig.resolve(SimpleConfig.java:69)
    at com.typesafe.config.impl.SimpleConfig.resolve(SimpleConfig.java:42)
    at com.typesafe.config.ConfigFactory.load(ConfigFactory.java:219)
    at com.typesafe.config.ConfigFactory.load(ConfigFactory.java:119)
    at com.typesafe.config.ConfigFactory.load(ConfigFactory.java:79)
    at com.typesafe.config.impl.ConfigTest.overrideUsingEnvVarAtChildLevel(ConfigTest.scala:1367)

[lightbend-cla-validator]

Hi @yantonov,

Thank you for your contribution! We really value the time you've taken to put this together.

Before we proceed with reviewing this pull request, please sign the Lightbend Contributors License Agreement:

https://www.lightbend.com/contribute/cla

[ennru]

We do not intend to extend the functionality of "Typesafe Config" further. See https://github.com/lightbend/config#maintained-by