MP-Config 1.2.1: getPropertyNames() implementation question

[Laird Nelson]

The specification says only this little bit about mutable data (https://github.com/eclipse/microprofile-config/blob/master/spec/src/main/asciidoc/configsources.asciidoc#configsource-and-mutable-data):

A Config instance provides no caching [1] but iterates over all ConfigSources for each getValue(String) operation. A ConfigSource is allowed to cache the underlying values itself.

This ([1]) suggests to me, but does not specify, that Config.getPropertyNames() must not cache the results of its ConfigSource#getPropertyNames() invocations.

In other words, must my implementation of Config#getPropertyNames() look like this (pseudocode, typed without checking):

Set<String> allPropertyNames = new HashSet<>();

for (final ConfigSource myConfigSource : myConfigSources) {

  allPropertyNames.addAll(myConfigSource.getPropertyNames());

}

return allPropertyNames;

The javadoc for Config#getPropertyNames() (https://static.javadoc.io/org.eclipse.microprofile.config/microprofile-config-api/1.2.1/org/eclipse/microprofile/config/Config.html#getPropertyNames--) says nothing on this subject.

Is this entire area undefined?

Thanks,

Best,

Laird

[Laird Nelson]

I filed an issue and commented on it: https://github.com/eclipse/microprofile-config/issues/370#issuecomment-395843292