InternetDomainName.topPrivateDomain() throws exception for Amazonaws-Domain

[kindlerm1958]

Description

We just noticed that the method InternetDomainName.topPrivateDomain() throws an IllegalStateException for the host s3-eu-west-1.amazonaws.com. Strange: replacing the "s3" by something else works as expected.

Example

import com.google.common.net.InternetDomainName; 

public class GuavaTest {

	public static void main(String[] args) {
		final String host = "s3-eu-west-1.amazonaws.com"; //s4-eu-west-1.amazonaws.com works
		
		InternetDomainName domainName = InternetDomainName.from(host);
		if (domainName.hasPublicSuffix()) {
			System.out.println(host + " hasPublicSuffix");
            System.out.println("topPrivateDomain: " + domainName.topPrivateDomain().toString());
        }

	}

}

Expected Behavior

s3-eu-west-1.amazonaws.com hasPublicSuffix
topPrivateDomain: amazonaws.com

Actual Behavior

s3-eu-west-1.amazonaws.com hasPublicSuffix
Exception in thread "main" java.lang.IllegalStateException: Not under a public suffix: s3-eu-west-1.amazonaws.com
at com.google.common.base.Preconditions.checkState(Preconditions.java:604)
at com.google.common.net.InternetDomainName.topPrivateDomain(InternetDomainName.java:466)
at de.swr.online.GuavaTest.main(GuavaTest.java:13)

Packages

No response

Platforms

Java 8, Java 11, Java 17

Checklist

• I agree to follow the code of conduct.

[cpovirk]

s3-eu-west-1.amazonaws.com is itself a public suffix, so it does not have a private domain.

[kindlerm1958]

I see.
So it is not safe to do the following (as we currently do):
if (domainName.hasPublicSuffix()) {
return domainName.topPrivateDomain().toString();
}
?
We will have to check wheter domainName IS a pubic suffix not just whether it has one?

[cpovirk]

If you want to know whether topPrivateDomain() is safe to call, then the method to call is isUnderPublicSuffix(), rather than hasPublicSuffix().

[kindlerm1958]

Thanks a lot! Now it works as expected