SOLR-15421 ConfigSetService.checkConfigExists accepts empty configs

[asalamon74]

Description

Both FileSystemConfigSetService and ZkConfigSetService only checks the existence of the directory only in checkConfigExists.

Solution

Create a new method to also check for solrconfig.xml checkConfigExistsWithSolrConfigXml

Tests

Checklist

Please review the following and check all that apply:

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• I have created a Jira issue and added the issue ID to my pull request title.
• I have given Solr maintainers access to contribute to my PR branch. (optional but recommended)
• I have developed this patch against the main branch.
• I have run ./gradlew check.
• I have added tests for my changes.
• I have added documentation for the Reference Guide

[HoustonPutman]

If there is a existsConfig == null check above, there should be one here as well, otherwise there will be a NPE.

[asalamon74]

Good point, fixed.

[dsmiley]

I'm missing something; why two calls to ZK just to check that a config exists? If solrconfig.xml is now necessary, then why check the parent?

[asalamon74]

Fxied

[dsmiley]

I'm missing something; why two calls to ZK just to check that a config exists? If solrconfig.xml is now necessary, then why check the parent?

[dsmiley]

Why the isDirectory check; why not just check for solrconfig.xml?

[asalamon74]

Fixed

[dsmiley]

LGTM. Can you add a CHANGES.txt entry please? Under 9.0 Improvements. Try to explain briefly in a way a user would understand.

[asalamon74]

Thanks @dsmiley I added the CHANGES.txt entry and also changed the commit message to match it. Feel free to suggest a new text if necessary.