Change ConfigFactory/SimpleConfigObject def to no paren

[mdedetrich]

While working on apache/pekko#2187, as part of doing this migration I noticed that I had to change ConfigFactory.empty to ConfigFactory.empty(). In Scala its idiomatic to have empty parens only on methods that create side effects and ConfigFactor.empty has no side effects (its a pure value). Other parts of sconfig already do this (i.e. see ValueType which is correctly missing parens) so I think that having the parens on ConfigFactory/SimpleConfigObject may have been an oversight.

This change may be source breaking (newer versions of Scala have deprecated the ability to automatically remove empty parens if the method definition has empty parens and vice versa depending on deprecation flags) but its not breaking binary compatibility in any way. The worst that users may have to experience is they would have to remove the parens from ConfigFactory.empty() in their Scala source code when updating sconfig to a release that his this fix. Java users are entirely unaffected (in Java you always have these parens for functions, regardless of how its defined in Scala).

[ekrich]

This looks good. It may be possible that we missed other sites as well. Do you mind adding a scalafix rule for this as well?

[mdedetrich]

This looks good. It may be possible that we missed other sites as well. Do you mind adding a scalafix rule for this as well?

So the ScalaFix rule is actually correct, it translated com.typesafe.config.ConfigObject.empty() to the parenless org.ekrich.config.ConfigObject.empty (see https://github.com/mdedetrich/sconfig/blob/be3e46adf497298b0bfa7c603d4fd924f2543d4a/scalafix/rules/src/main/scala/org/ekrich/sconfig/fix/ReplaceTypesafeConfig.scala#L44-L52). When I ran the migration tool on Pekko, I actually had to manually afterwards change org.ekrich.config.ConfigObject.empty to org.ekrich.config.ConfigObject.empty() because the actual definition had parens (which this PR fixes).

Given this I don't think there is anything that needs to be done unless I misunderstood something?

[ekrich]

I didn't think to look. Thanks.

[ekrich]

LGTM

[He-Pin]

There are some pending pr in the lightbend configuration, can we have them.here？