NPE in DefaultClientFactory.newClient

[mauhiz]

Version : 1.11

Caused by: java.lang.NullPointerException
        at com.linecorp.armeria.client.DefaultClientFactory.newClient(DefaultClientFactory.java:174)
        at com.linecorp.armeria.client.ClientBuilder.build(ClientBuilder.java:112)

I'm seeing this NPE trying to connect to the scheme gproto+h2c. It works locally and fails only on a uber jar.
Definitely something is missing or mis-configured, but the error is just too cryptic...

Investigation results

The actual factory is a UnaryGrpcClientFactory (added in #3773) and its condition to accept a clientType is clientType == UnaryGrpcClient.class. Why is the other factory (GrpcClientFactory) not present?

It's reference via a ServiceLoader config file, which is present in the uber jar;
Actually both service loader config files are present (duplicate entries).
Fixing the jar building process to merge the service properties into a single com.linecorp.armeria.client.ClientFactoryProvider jar entry fixed the concrete issue.

Finally

• It would have saved me time if I knew that a factory is missing : making the error more explicit in #3867 Make explicit the failure to find a suitable ClientFactory #3868
• My failing to build an uber jar is not related to how Armeria is built, so won't fix anything related, but keeping it here for reference