Forward SegmentDirectoryLoaderContext in DefaultSegmentDirectoryLoader

[raghavyadav01]

What

#18806 ("Replace segmentDirectoryConfigs map with ReadMode in SegmentDirectoryLoaderContext") refactored DefaultSegmentDirectoryLoader.load and inadvertently dropped the segmentLoaderContext argument when constructing SegmentLocalFSDirectory:

// Before #18806
return new SegmentLocalFSDirectory(directory, segmentLoaderContext,
    ReadMode.valueOf(segmentDirectoryConfigs.getProperty(IndexLoadingConfig.READ_MODE_KEY)));

// After #18806 (current master)
return new SegmentLocalFSDirectory(directory, segmentLoaderContext.getReadMode());

The 2-arg SegmentLocalFSDirectory(File, ReadMode) constructor sets the underlying SingleFileIndexDirectory#_segmentDirectoryLoaderContext to null. This silently breaks the task-config propagation introduced in #18264 — SingleFileIndexDirectory#serializeTaskConfigToJsonFromContext() short-circuits at its first guard:

private String serializeTaskConfigToJsonFromContext() {
  if (_segmentDirectoryLoaderContext == null) {
    return null;     // ← #18806 makes this always true on the default loader path
  }
  ...
}

As a result, task.config.json is never injected into EmptyIndexBuffer.properties, and downstream consumers that depend on the table's task configuration to resolve their own configuration silently fall back to ambient defaults

[Jackie-Jiang]

Good catch

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 37.18%. Comparing base (3be6236) to head (a09daac).

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18863      +/-   ##
============================================
+ Coverage     37.16%   37.18%   +0.01%     
  Complexity     1321     1321              
============================================
  Files          3393     3393              
  Lines        211305   211306       +1     
  Branches      33226    33226              
============================================
+ Hits          78541    78578      +37     
+ Misses       125557   125519      -38     
- Partials       7207     7209       +2     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (ø)
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-21	37.18% <100.00%> (+0.01%)	⬆️
temurin	37.18% <100.00%> (+0.01%)	⬆️
unittests	37.18% <100.00%> (+0.01%)	⬆️
unittests2	37.18% <100.00%> (+0.01%)	⬆️

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