SOLR-17153: Resolve IndexOutOfBoundsException in HttpSolrCall.resolveDocCollection()

[aparnasuresh85]

https://issues.apache.org/jira/browse/SOLR-17153

Description

Resolve an IndexOutOfBoundsException in HttpSolrCall.resolveDocCollection(), at line:
String collectionName = collectionsList.get(0);

Solution

Check if collectionsList is empty, in that case return early.

Tests

Ensured existing tests pass

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

[dsmiley]

+1 to the change.
needs "tidy" clearly (you don't have a space to the left of the parenthesis)

Also something was eating at it me a bit... the method you added, resolveDocCollection, returns a DocCollection but in HttpSolrCall.init you added a call to it that does nothing with the response. Feels weird. Instead, shouldn't HttpSolrCall.getCoreByCollection use this method?

[dsmiley]

This PR looks weird; looks like the old PR but one commit added. Should be a new PR.

[aparnasuresh85]

+1 to the change. needs "tidy" clearly (you don't have a space to the left of the parenthesis)

Also something was eating at it me a bit... the method you added, resolveDocCollection, returns a DocCollection but in HttpSolrCall.init you added a call to it that does nothing with the response. Feels weird. Instead, shouldn't HttpSolrCall.getCoreByCollection use this method?

I agree. The reason I kept the call to resolveDocCollection() outside of getCoreByCollection() is because the doc around the latter (if getCoreByCollection returned null ) said "// this collection exists , but this node does not have a replica for that collection".

Instead, should we throw a SolrException (collection or alias not found) if inside getCoreByCollection, the call to resolveDocCollection() returned null?

[aparnasuresh85]

+1 to the change. needs "tidy" clearly (you don't have a space to the left of the parenthesis)
Also something was eating at it me a bit... the method you added, resolveDocCollection, returns a DocCollection but in HttpSolrCall.init you added a call to it that does nothing with the response. Feels weird. Instead, shouldn't HttpSolrCall.getCoreByCollection use this method?

I agree. The reason I kept the call to resolveDocCollection() outside of getCoreByCollection() is because the doc around the latter (if getCoreByCollection returned null ) said "// this collection exists , but this node does not have a replica for that collection".

Instead, should we throw a SolrException (collection or alias not found) if inside getCoreByCollection, the call to resolveDocCollection() returned null?

Maybe not. I see a number of tests fail if an exception is thrown in case collection is null from resolveDocCollection(). The tests pass otherwise. I will send a new PR.