Fix ClassCastException when using dynamic template with flat_object mapping and dots in field names

[cwperks]

Description

Opening a draft PR to solicit feedback. This fixes an issue that can cause the DocumentParser to throw a ClassCastException when there is a dynamic template with a flat_object mapping and trying to index a document that contains field names with dots.

Instead of the ClassCastException, this PR will still fail the request but with a more descriptive error message saying that dots in field names is forbidden using a dynamic template with flat_object mapping. This is similar to existing behavior with dynamic templates with a nested mapping. See similar test.

Related Issues

Resolves #12298

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)
• Public documentation issue/PR created

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[reta]

@cwperks it supposed to be fixed by #11425, tldr;' the field names with dots should be handled properly I believe, if it is not the case - the previous fix looks incomplete, @msfroh fyi

[cwperks]

@reta I can reproduce the issue described in #12298 using the steps provided. The test I wrote will also throw the ClassCastException without the corresponding change in DocumentParser.java.

[github-actions]

Compatibility status:

Checks if related components are compatible with change fce90d2

Incompatible components

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/flow-framework.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/opensearch-oci-object-storage.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/performance-analyzer.git]

[reta]

@reta I can reproduce the issue described in #12298 using the steps provided. The test I wrote will also throw the ClassCastException without the corresponding change in DocumentParser.java.

@cwperks sure, the issue is there, the fix was incomplete?

[github-actions]

❌ Gradle check result for b886c7e: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❕ Gradle check result for fce90d2: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.index.shard.RemoteIndexShardTests.testNRTReplicaWithRemoteStorePromotedAsPrimaryCommitCommit

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.48%. Comparing base (b15cb0c) to head (fce90d2).
Report is 133 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13081      +/-   ##
============================================
+ Coverage     71.42%   71.48%   +0.06%     
- Complexity    59978    60462     +484     
============================================
  Files          4985     5026      +41     
  Lines        282275   284456    +2181     
  Branches      40946    41197     +251     
============================================
+ Hits         201603   203350    +1747     
- Misses        63999    64311     +312     
- Partials      16673    16795     +122     

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[cwperks]

Closing this PR in favor of revisiting #11425 for completeness. Thank you @reta!