[AstonKrss]

Resolves #7949

Motivation

Errors raised while interpreting declarative configuration were generic and
ambiguous, and did not tell you where in the document the problem was:

batch span processor exporter is required but is null

A document can contain several processors, so this is hard to act on. The issue
asks for the message to include the path to the offending node:

.tracer_provider.processors[0].batch exporter is required but is null

Implementation

DeclarativeConfigContext now tracks the path of the configuration node
currently being interpreted:

• getConfigPath() returns "" at the root, otherwise "." + join(".", segments).
• withConfigPath(segment, supplier) pushes/pops around a supplier (restores in finally).
• pushConfigPath(segment) / popConfigPath() for statement-style call sites
  (loops and multi-statement blocks) where a lambda is awkward or where NullAway
  cannot carry the null-check of a nullable getter into the lambda.

FileConfigUtil.requireNonNull(context, object, description) prefixes the message
with getConfigPath(), and a new FileConfigUtil.withConfigPath(context, message)
helper covers messages that are not built via requireNonNull.

Each factory descends into its children by pushing a path segment named after the
corresponding configuration model field, so the segment matches the documented key:

Factory	Segments
OpenTelemetryConfigurationFactory	propagator, resource, meter_provider, logger_provider, tracer_provider
TracerProviderFactory	sampler, processors[i], id_generator, tracer_configurator/development.tracers[i]
LoggerProviderFactory	processors[i], logger_configurator/development.loggers[i]
MeterProviderFactory	readers[i], views[i], meter_configurator/development.meters[i]
MetricReaderFactory	periodic, pull
SpanProcessorFactory	batch, simple
LogRecordProcessorFactory	batch, simple
SamplerFactory	always_record
ComposableSamplerFactory	rule_based, parent_threshold
ComposableRuleBasedSamplerFactory	rules[i], attribute_values, attribute_patterns
AttributeListFactory	attributes[i]

Before / after

- batch span processor exporter is required but is null
+ .tracer_provider.processors[0].batch exporter is required but is null

- always_record sampler .root is required
+ .tracer_provider.sampler.always_record root is required but is null

- parent threshold sampler root is required but is null
+ .tracer_provider.sampler.parent_threshold root is required but is null

Testing

• New end-to-end test parseAndCreate_ErrorIncludesDocumentPath in
  DeclarativeConfigurationCreateTest reproduces the exact scenario from the issue
  (YAML with tracer_provider.processors[0].batch missing exporter).
• Updated expectations in SpanProcessorFactoryTest, LogRecordProcessorFactoryTest,
  MetricReaderFactoryTest, and SamplerFactoryTest; the factory calls are now wrapped
  in the corresponding withConfigPath(...) so the assertions verify the real document path.

./gradlew :sdk-extensions:declarative-config:test        # 541 tests, 0 failures
./gradlew :sdk-extensions:declarative-config:spotlessCheck

Notes

• Change is limited to the declarative-config module and does not alter the public API surface.
• NullAway (enforced in this repo) requires nullable getters to be hoisted into a local
  variable before use inside a lambda, which is why some call sites use
  push/popConfigPath in try/finally rather than withConfigPath.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: AstonKrss / name: AstonKrss (d498416)

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[codecov]

Codecov Report

❌ Patch coverage is 96.98492% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.68%. Comparing base (1522a4d) to head (d498416).

Files with missing lines	Patch %	Lines
...nfigure/declarativeconfig/MetricReaderFactory.java	75.00%	2 Missing and 1 partial ⚠️
...ativeconfig/ComposableRuleBasedSamplerFactory.java	94.87%	0 Missing and 2 partials ⚠️
...re/declarativeconfig/ComposableSamplerFactory.java	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8953      +/-   ##
============================================
+ Coverage     90.66%   90.68%   +0.02%     
- Complexity    10888    10914      +26     
============================================
  Files          1015     1015              
  Lines         29736    29806      +70     
  Branches       3877     3882       +5     
============================================
+ Hits          26959    27029      +70     
- Misses         1860     1861       +1     
+ Partials        917      916       -1     

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